freebsd-nq/man/man8/zfs.8

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.\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
.\" Copyright 2011 Joshua M. Clulow <josh@sysmgr.org>
.\" Copyright (c) 2011, 2016 by Delphix. All rights reserved.
.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
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.\" Copyright (c) 2014 Integros [integros.com]
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.Dd June 28, 2017
.Dt ZFS 8 SMM
.Os Linux
.Sh NAME
.Nm zfs
.Nd configures ZFS file systems
.Sh SYNOPSIS
.Nm
.Fl ?
.Nm
.Cm create
.Op Fl p
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Ar filesystem
.Nm
.Cm create
.Op Fl ps
.Op Fl b Ar blocksize
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Fl V Ar size Ar volume
.Nm
.Cm destroy
.Op Fl Rfnprv
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm destroy
.Op Fl Rdnprv
.Ar filesystem Ns | Ns Ar volume Ns @ Ns Ar snap Ns
.Oo % Ns Ar snap Ns Oo , Ns Ar snap Ns Oo % Ns Ar snap Oc Oc Oc Ns ...
.Nm
.Cm destroy
.Ar filesystem Ns | Ns Ar volume Ns # Ns Ar bookmark
.Nm
.Cm snapshot
.Op Fl r
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Ar filesystem Ns @ Ns Ar snapname Ns | Ns Ar volume Ns @ Ns Ar snapname Ns ...
.Nm
.Cm rollback
.Op Fl Rfr
.Ar snapshot
.Nm
.Cm clone
.Op Fl p
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Ar snapshot Ar filesystem Ns | Ns Ar volume
.Nm
.Cm promote
.Ar clone-filesystem
.Nm
.Cm rename
.Op Fl f
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Nm
.Cm rename
.Op Fl fp
.Ar filesystem Ns | Ns Ar volume
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm rename
.Fl r
.Ar snapshot Ar snapshot
.Nm
.Cm list
.Op Fl r Ns | Ns Fl d Ar depth
.Op Fl Hp
.Oo Fl o Ar property Ns Oo , Ns Ar property Oc Ns ... Oc
.Oo Fl s Ar property Oc Ns ...
.Oo Fl S Ar property Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Oo Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Oc Ns ...
.Nm
.Cm set
.Ar property Ns = Ns Ar value Oo Ar property Ns = Ns Ar value Oc Ns ...
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns ...
.Nm
.Cm get
.Op Fl r Ns | Ns Fl d Ar depth
.Op Fl Hp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar source Ns Oo , Ns Ar source Oc Ns ... Oc
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Cm all | Ar property Ns Oo , Ns Ar property Oc Ns ...
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns | Ns Ar bookmark Ns ...
.Nm
.Cm inherit
.Op Fl rS
.Ar property Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns ...
.Nm
.Cm upgrade
.Nm
.Cm upgrade
.Fl v
.Nm
.Cm upgrade
.Op Fl r
.Op Fl V Ar version
.Fl a | Ar filesystem
.Nm
.Cm userspace
.Op Fl Hinp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar field Oc Ns ...
.Oo Fl S Ar field Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar snapshot
.Nm
.Cm groupspace
.Op Fl Hinp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar field Oc Ns ...
.Oo Fl S Ar field Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar snapshot
.Nm
.Cm mount
.Nm
.Cm mount
.Op Fl Olv
.Op Fl o Ar options
.Fl a | Ar filesystem
.Nm
.Cm unmount
.Op Fl f
.Fl a | Ar filesystem Ns | Ns Ar mountpoint
.Nm
.Cm share
.Fl a | Ar filesystem
.Nm
.Cm unshare
.Fl a | Ar filesystem Ns | Ns Ar mountpoint
.Nm
.Cm bookmark
.Ar snapshot bookmark
.Nm
.Cm send
.Op Fl DLPRcenpvw
.Op Oo Fl I Ns | Ns Fl i Oc Ar snapshot
.Ar snapshot
.Nm
.Cm send
.Op Fl LPcenvw
.Op Fl i Ar snapshot Ns | Ns Ar bookmark
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Nm
.Cm send
.Op Fl Penv
.Fl t Ar receive_resume_token
.Nm
.Cm receive
.Op Fl Fnsuv
.Op Fl o Sy origin Ns = Ns Ar snapshot
.Op Fl o Ar property Ns = Ns Ar value
.Op Fl x Ar property
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Nm
.Cm receive
.Op Fl Fnsuv
.Op Fl d Ns | Ns Fl e
.Op Fl o Sy origin Ns = Ns Ar snapshot
.Op Fl o Ar property Ns = Ns Ar value
.Op Fl x Ar property
.Ar filesystem
.Nm
.Cm receive
.Fl A
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm allow
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm allow
.Op Fl dglu
.Ar user Ns | Ns Ar group Ns Oo , Ns Ar user Ns | Ns Ar group Oc Ns ...
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm allow
.Op Fl dl
.Fl e Ns | Ns Sy everyone
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm allow
.Fl c
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm allow
.Fl s No @ Ns Ar setname
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm unallow
.Op Fl dglru
.Ar user Ns | Ns Ar group Ns Oo , Ns Ar user Ns | Ns Ar group Oc Ns ...
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm unallow
.Op Fl dlr
.Fl e Ns | Ns Sy everyone
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm unallow
.Op Fl r
.Fl c
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm unallow
.Op Fl r
.Fl s @ Ns Ar setname
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Nm
.Cm hold
.Op Fl r
.Ar tag Ar snapshot Ns ...
.Nm
.Cm holds
.Op Fl r
.Ar snapshot Ns ...
.Nm
.Cm release
.Op Fl r
.Ar tag Ar snapshot Ns ...
.Nm
.Cm diff
.Op Fl FHt
.Ar snapshot Ar snapshot Ns | Ns Ar filesystem
.Nm
.Cm load-key
.Op Fl nr
.Op Fl L Ar keylocation
.Fl a | Ar filesystem
.Nm
.Cm unload-key
.Op Fl r
.Fl a | Ar filesystem
.Nm
.Cm change-key
.Op Fl l
.Op Fl o Ar keylocation Ns = Ns Ar value
.Op Fl o Ar keyformat Ns = Ns Ar value
.Op Fl o Ar pbkdf2iters Ns = Ns Ar value
.Ar filesystem
.Nm
.Cm change-key
.Fl i
.Op Fl l
.Ar filesystem
.Sh DESCRIPTION
The
.Nm
command configures ZFS datasets within a ZFS storage pool, as described in
.Xr zpool 8 .
A dataset is identified by a unique path within the ZFS namespace.
For example:
.Bd -literal
pool/{filesystem,volume,snapshot}
.Ed
.Pp
where the maximum length of a dataset name is
.Dv MAXNAMELEN
.Pq 256 bytes .
.Pp
A dataset can be one of the following:
.Bl -tag -width "file system"
.It Sy file system
A ZFS dataset of type
.Sy filesystem
can be mounted within the standard system namespace and behaves like other file
systems.
While ZFS file systems are designed to be POSIX compliant, known issues exist
that prevent compliance in some cases.
Applications that depend on standards conformance might fail due to non-standard
behavior when checking file system free space.
.It Sy volume
A logical volume exported as a raw or block device.
This type of dataset should only be used under special circumstances.
File systems are typically used in most environments.
.It Sy snapshot
A read-only version of a file system or volume at a given point in time.
It is specified as
.Ar filesystem Ns @ Ns Ar name
or
.Ar volume Ns @ Ns Ar name .
.It Sy bookmark
Much like a
.Sy snapshot ,
but without the hold on on-disk data. It can be used as the source of a send
(but not for a receive). It is specified as
.Ar filesystem Ns # Ns Ar name
or
.Ar volume Ns # Ns Ar name .
.El
.Ss ZFS File System Hierarchy
A ZFS storage pool is a logical collection of devices that provide space for
datasets.
A storage pool is also the root of the ZFS file system hierarchy.
.Pp
The root of the pool can be accessed as a file system, such as mounting and
unmounting, taking snapshots, and setting properties.
The physical storage characteristics, however, are managed by the
.Xr zpool 8
command.
.Pp
See
.Xr zpool 8
for more information on creating and administering pools.
.Ss Snapshots
A snapshot is a read-only copy of a file system or volume.
Snapshots can be created extremely quickly, and initially consume no additional
space within the pool.
As data within the active dataset changes, the snapshot consumes more data than
would otherwise be shared with the active dataset.
.Pp
Snapshots can have arbitrary names.
Snapshots of volumes can be cloned or rolled back, visibility is determined
by the
.Sy snapdev
property of the parent volume.
.Pp
File system snapshots can be accessed under the
.Pa .zfs/snapshot
directory in the root of the file system.
Snapshots are automatically mounted on demand and may be unmounted at regular
intervals.
The visibility of the
.Pa .zfs
directory can be controlled by the
.Sy snapdir
property.
.Ss Bookmarks
A bookmark is like a snapshot, a read-only copy of a file system or volume.
Bookmarks can be created extremely quickly, compared to snapshots, and they
consume no additional space within the pool. Bookmarks can also have arbitrary
names, much like snapshots.
.Pp
Unlike snapshots, bookmarks can not be accessed through the filesystem in any
way. From a storage standpoint a bookmark just provides a way to reference
when a snapshot was created as a distinct object. Bookmarks are initially
tied to a snapshot, not the filesystem or volume, and they will survive if the
snapshot itself is destroyed. Since they are very light weight there's little
incentive to destroy them.
.Ss Clones
A clone is a writable volume or file system whose initial contents are the same
as another dataset.
As with snapshots, creating a clone is nearly instantaneous, and initially
consumes no additional space.
.Pp
Clones can only be created from a snapshot.
When a snapshot is cloned, it creates an implicit dependency between the parent
and child.
Even though the clone is created somewhere else in the dataset hierarchy, the
original snapshot cannot be destroyed as long as a clone exists.
The
.Sy origin
property exposes this dependency, and the
.Cm destroy
command lists any such dependencies, if they exist.
.Pp
The clone parent-child dependency relationship can be reversed by using the
.Cm promote
subcommand.
This causes the
.Qq origin
file system to become a clone of the specified file system, which makes it
possible to destroy the file system that the clone was created from.
.Ss "Mount Points"
Creating a ZFS file system is a simple operation, so the number of file systems
per system is likely to be numerous.
To cope with this, ZFS automatically manages mounting and unmounting file
systems without the need to edit the
.Pa /etc/fstab
file.
All automatically managed file systems are mounted by ZFS at boot time.
.Pp
By default, file systems are mounted under
.Pa /path ,
where
.Ar path
is the name of the file system in the ZFS namespace.
Directories are created and destroyed as needed.
.Pp
A file system can also have a mount point set in the
.Sy mountpoint
property.
This directory is created as needed, and ZFS automatically mounts the file
system when the
.Nm zfs Cm mount Fl a
command is invoked
.Po without editing
.Pa /etc/fstab
.Pc .
The
.Sy mountpoint
property can be inherited, so if
.Em pool/home
has a mount point of
.Pa /export/stuff ,
then
.Em pool/home/user
automatically inherits a mount point of
.Pa /export/stuff/user .
.Pp
A file system
.Sy mountpoint
property of
.Sy none
prevents the file system from being mounted.
.Pp
If needed, ZFS file systems can also be managed with traditional tools
.Po
.Nm mount ,
.Nm umount ,
.Pa /etc/fstab
.Pc .
If a file system's mount point is set to
.Sy legacy ,
ZFS makes no attempt to manage the file system, and the administrator is
responsible for mounting and unmounting the file system. Because pools must
be imported before a legacy mount can succeed, administrators should ensure
that legacy mounts are only attempted after the zpool import process
finishes at boot time. For example, on machines using systemd, the mount
option
.Pp
.Nm x-systemd.requires=zfs-import.target
.Pp
will ensure that the zfs-import completes before systemd attempts mounting
the filesystem. See systemd.mount(5) for details.
.Ss Deduplication
Deduplication is the process for removing redundant data at the block level,
reducing the total amount of data stored. If a file system has the
.Sy dedup
property enabled, duplicate data blocks are removed synchronously. The result
is that only unique data is stored and common components are shared among files.
.Pp
Deduplicating data is a very resource-intensive operation. It is generally
recommended that you have at least 1.25 GiB of RAM per 1 TiB of storage when
you enable deduplication. Calculating the exact requirement depends heavily
on the type of data stored in the pool.
.Pp
Enabling deduplication on an improperly-designed system can result in
performance issues (slow IO and administrative operations). It can potentially
lead to problems importing a pool due to memory exhaustion. Deduplication
can consume significant processing power (CPU) and memory as well as generate
additional disk IO.
.Pp
Before creating a pool with deduplication enabled, ensure that you have planned
your hardware requirements appropriately and implemented appropriate recovery
practices, such as regular backups. As an alternative to deduplication
consider using
.Sy compression=on ,
as a less resource-intensive alternative.
.Ss Native Properties
Properties are divided into two types, native properties and user-defined
.Po or
.Qq user
.Pc
properties.
Native properties either export internal statistics or control ZFS behavior.
In addition, native properties are either editable or read-only.
User properties have no effect on ZFS behavior, but you can use them to annotate
datasets in a way that is meaningful in your environment.
For more information about user properties, see the
.Sx User Properties
section, below.
.Pp
Every dataset has a set of properties that export statistics about the dataset
as well as control various behaviors.
Properties are inherited from the parent unless overridden by the child.
Some properties apply only to certain types of datasets
.Pq file systems, volumes, or snapshots .
.Pp
The values of numeric properties can be specified using human-readable suffixes
.Po for example,
.Sy k ,
.Sy KB ,
.Sy M ,
.Sy Gb ,
and so forth, up to
.Sy Z
for zettabyte
.Pc .
The following are all valid
.Pq and equal
specifications:
.Li 1536M, 1.5g, 1.50GB .
.Pp
The values of non-numeric properties are case sensitive and must be lowercase,
except for
.Sy mountpoint ,
.Sy sharenfs ,
and
.Sy sharesmb .
.Pp
The following native properties consist of read-only statistics about the
dataset.
These properties can be neither set, nor inherited.
Native properties apply to all dataset types unless otherwise noted.
.Bl -tag -width "usedbyrefreservation"
.It Sy available
The amount of space available to the dataset and all its children, assuming that
there is no other activity in the pool.
Because space is shared within a pool, availability can be limited by any number
of factors, including physical pool size, quotas, reservations, or other
datasets within the pool.
.Pp
This property can also be referred to by its shortened column name,
.Sy avail .
.It Sy compressratio
For non-snapshots, the compression ratio achieved for the
.Sy used
space of this dataset, expressed as a multiplier.
The
.Sy used
property includes descendant datasets, and, for clones, does not include the
space shared with the origin snapshot.
For snapshots, the
.Sy compressratio
is the same as the
.Sy refcompressratio
property.
Compression can be turned on by running:
.Nm zfs Cm set Sy compression Ns = Ns Sy on Ar dataset .
The default value is
.Sy off .
.It Sy createtxg
The transaction group (txg) in which the dataset was created. Bookmarks have
the same
.Sy createtxg
as the snapshot they are initially tied to. This property is suitable for
ordering a list of snapshots, e.g. for incremental send and receive.
.It Sy creation
The time this dataset was created.
.It Sy clones
For snapshots, this property is a comma-separated list of filesystems or volumes
which are clones of this snapshot.
The clones'
.Sy origin
property is this snapshot.
If the
.Sy clones
property is not empty, then this snapshot can not be destroyed
.Po even with the
.Fl r
or
.Fl f
options
.Pc .
The roles of origin and clone can be swapped by promoting the clone with the
.Nm zfs Cm promote
command.
.It Sy defer_destroy
This property is
.Sy on
if the snapshot has been marked for deferred destroy by using the
.Nm zfs Cm destroy Fl d
command.
Otherwise, the property is
.Sy off .
.It Sy encryptionroot
For encrypted datasets, indicates where the dataset is currently inheriting its
encryption key from. Loading or unloading a key for the
.Sy encryptionroot
will implicitly load / unload the key for any inheriting datasets (see
.Nm zfs Cm load-key
and
.Nm zfs Cm unload-key
for details).
Clones will always share an
encryption key with their origin. See the
.Sx Encryption
section for details.
.It Sy filesystem_count
The total number of filesystems and volumes that exist under this location in
the dataset tree.
This value is only available when a
.Sy filesystem_limit
has been set somewhere in the tree under which the dataset resides.
.It Sy keystatus
Indicates if an encryption key is currently loaded into ZFS. The possible
values are
.Sy none ,
.Sy available ,
and
.Sy unavailable .
See
.Nm zfs Cm load-key
and
.Nm zfs Cm unload-key .
.It Sy guid
The 64 bit GUID of this dataset or bookmark which does not change over its
entire lifetime. When a snapshot is sent to another pool, the received
snapshot has the same GUID. Thus, the
.Sy guid
is suitable to identify a snapshot across pools.
.It Sy logicalreferenced
The amount of space that is
.Qq logically
accessible by this dataset.
See the
.Sy referenced
property.
The logical space ignores the effect of the
.Sy compression
and
.Sy copies
properties, giving a quantity closer to the amount of data that applications
see.
However, it does include space consumed by metadata.
.Pp
This property can also be referred to by its shortened column name,
.Sy lrefer .
.It Sy logicalused
The amount of space that is
.Qq logically
consumed by this dataset and all its descendents.
See the
.Sy used
property.
The logical space ignores the effect of the
.Sy compression
and
.Sy copies
properties, giving a quantity closer to the amount of data that applications
see.
However, it does include space consumed by metadata.
.Pp
This property can also be referred to by its shortened column name,
.Sy lused .
.It Sy mounted
For file systems, indicates whether the file system is currently mounted.
This property can be either
.Sy yes
or
.Sy no .
.It Sy origin
For cloned file systems or volumes, the snapshot from which the clone was
created.
See also the
.Sy clones
property.
.It Sy receive_resume_token
For filesystems or volumes which have saved partially-completed state from
.Sy zfs receive -s ,
this opaque token can be provided to
.Sy zfs send -t
to resume and complete the
.Sy zfs receive .
.It Sy referenced
The amount of data that is accessible by this dataset, which may or may not be
shared with other datasets in the pool.
When a snapshot or clone is created, it initially references the same amount of
space as the file system or snapshot it was created from, since its contents are
identical.
.Pp
This property can also be referred to by its shortened column name,
.Sy refer .
.It Sy refcompressratio
The compression ratio achieved for the
.Sy referenced
space of this dataset, expressed as a multiplier.
See also the
.Sy compressratio
property.
.It Sy snapshot_count
The total number of snapshots that exist under this location in the dataset
tree.
This value is only available when a
.Sy snapshot_limit
has been set somewhere in the tree under which the dataset resides.
.It Sy type
The type of dataset:
.Sy filesystem ,
.Sy volume ,
or
.Sy snapshot .
.It Sy used
The amount of space consumed by this dataset and all its descendents.
This is the value that is checked against this dataset's quota and reservation.
The space used does not include this dataset's reservation, but does take into
account the reservations of any descendent datasets.
The amount of space that a dataset consumes from its parent, as well as the
amount of space that is freed if this dataset is recursively destroyed, is the
greater of its space used and its reservation.
.Pp
The used space of a snapshot
.Po see the
.Sx Snapshots
section
.Pc
is space that is referenced exclusively by this snapshot.
If this snapshot is destroyed, the amount of
.Sy used
space will be freed.
Space that is shared by multiple snapshots isn't accounted for in this metric.
When a snapshot is destroyed, space that was previously shared with this
snapshot can become unique to snapshots adjacent to it, thus changing the used
space of those snapshots.
The used space of the latest snapshot can also be affected by changes in the
file system.
Note that the
.Sy used
space of a snapshot is a subset of the
.Sy written
space of the snapshot.
.Pp
The amount of space used, available, or referenced does not take into account
pending changes.
Pending changes are generally accounted for within a few seconds.
Committing a change to a disk using
.Xr fsync 2
or
.Dv O_SYNC
does not necessarily guarantee that the space usage information is updated
immediately.
.It Sy usedby*
The
.Sy usedby*
properties decompose the
.Sy used
properties into the various reasons that space is used.
Specifically,
.Sy used No =
.Sy usedbychildren No +
.Sy usedbydataset No +
.Sy usedbyrefreservation No +
.Sy usedbysnapshots .
These properties are only available for datasets created on
.Nm zpool
.Qo version 13 Qc
pools.
.It Sy usedbychildren
The amount of space used by children of this dataset, which would be freed if
all the dataset's children were destroyed.
.It Sy usedbydataset
The amount of space used by this dataset itself, which would be freed if the
dataset were destroyed
.Po after first removing any
.Sy refreservation
and destroying any necessary snapshots or descendents
.Pc .
.It Sy usedbyrefreservation
The amount of space used by a
.Sy refreservation
set on this dataset, which would be freed if the
.Sy refreservation
was removed.
.It Sy usedbysnapshots
The amount of space consumed by snapshots of this dataset.
In particular, it is the amount of space that would be freed if all of this
dataset's snapshots were destroyed.
Note that this is not simply the sum of the snapshots'
.Sy used
properties because space can be shared by multiple snapshots.
.It Sy userused Ns @ Ns Em user
The amount of space consumed by the specified user in this dataset.
Space is charged to the owner of each file, as displayed by
.Nm ls Fl l .
The amount of space charged is displayed by
.Nm du
and
.Nm ls Fl s .
See the
.Nm zfs Cm userspace
subcommand for more information.
.Pp
Unprivileged users can access only their own space usage.
The root user, or a user who has been granted the
.Sy userused
privilege with
.Nm zfs Cm allow ,
can access everyone's usage.
.Pp
The
.Sy userused Ns @ Ns Em ...
properties are not displayed by
.Nm zfs Cm get Sy all .
The user's name must be appended after the @ symbol, using one of the following
forms:
.Bl -bullet -width ""
.It
.Em POSIX name
.Po for example,
.Sy joe
.Pc
.It
.Em POSIX numeric ID
.Po for example,
.Sy 789
.Pc
.It
.Em SID name
.Po for example,
.Sy joe.smith@mydomain
.Pc
.It
.Em SID numeric ID
.Po for example,
.Sy S-1-123-456-789
.Pc
.El
.Pp
Files created on Linux always have POSIX owners.
.It Sy userobjused Ns @ Ns Em user
The
.Sy userobjused
property is similar to
.Sy userused
but instead it counts the number of objects consumed by a user. This property
counts all objects allocated on behalf of the user, it may differ from the
results of system tools such as
.Nm df Fl i .
.Pp
When the property
.Sy xattr=on
is set on a file system additional objects will be created per-file to store
extended attributes. These additional objects are reflected in the
.Sy userobjused
value and are counted against the user's
.Sy userobjquota .
When a file system is configured to use
.Sy xattr=sa
no additional internal objects are normally required.
.It Sy userrefs
This property is set to the number of user holds on this snapshot.
User holds are set by using the
.Nm zfs Cm hold
command.
.It Sy groupused Ns @ Ns Em group
The amount of space consumed by the specified group in this dataset.
Space is charged to the group of each file, as displayed by
.Nm ls Fl l .
See the
.Sy userused Ns @ Ns Em user
property for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupused
privilege with
.Nm zfs Cm allow ,
can access all groups' usage.
.It Sy groupobjused Ns @ Ns Em group
The number of objects consumed by the specified group in this dataset.
Multiple objects may be charged to the group for each file when extended
attributes are in use. See the
.Sy userobjused Ns @ Ns Em user
property for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupobjused
privilege with
.Nm zfs Cm allow ,
can access all groups' usage.
.It Sy volblocksize
For volumes, specifies the block size of the volume.
The
.Sy blocksize
cannot be changed once the volume has been written, so it should be set at
volume creation time.
The default
.Sy blocksize
for volumes is 8 Kbytes.
Any power of 2 from 512 bytes to 128 Kbytes is valid.
.Pp
This property can also be referred to by its shortened column name,
.Sy volblock .
.It Sy written
The amount of space
.Sy referenced
by this dataset, that was written since the previous snapshot
.Pq i.e. that is not referenced by the previous snapshot .
.It Sy written Ns @ Ns Em snapshot
The amount of
.Sy referenced
space written to this dataset since the specified snapshot.
This is the space that is referenced by this dataset but was not referenced by
the specified snapshot.
.Pp
The
.Em snapshot
may be specified as a short snapshot name
.Po just the part after the
.Sy @
.Pc ,
in which case it will be interpreted as a snapshot in the same filesystem as
this dataset.
The
.Em snapshot
may be a full snapshot name
.Po Em filesystem Ns @ Ns Em snapshot Pc ,
which for clones may be a snapshot in the origin's filesystem
.Pq or the origin of the origin's filesystem, etc.
.El
.Pp
The following native properties can be used to change the behavior of a ZFS
dataset.
.Bl -tag -width ""
.It Xo
.Sy aclinherit Ns = Ns Sy discard Ns | Ns Sy noallow Ns | Ns
.Sy restricted Ns | Ns Sy passthrough Ns | Ns Sy passthrough-x
.Xc
Controls how ACEs are inherited when files and directories are created.
.Bl -tag -width "passthrough-x"
.It Sy discard
does not inherit any ACEs.
.It Sy noallow
only inherits inheritable ACEs that specify
.Qq deny
permissions.
.It Sy restricted
default, removes the
.Sy write_acl
and
.Sy write_owner
permissions when the ACE is inherited.
.It Sy passthrough
inherits all inheritable ACEs without any modifications.
.It Sy passthrough-x
same meaning as
.Sy passthrough ,
except that the
.Sy owner@ ,
.Sy group@ ,
and
.Sy everyone@
ACEs inherit the execute permission only if the file creation mode also requests
the execute bit.
.El
.Pp
When the property value is set to
.Sy passthrough ,
files are created with a mode determined by the inheritable ACEs.
If no inheritable ACEs exist that affect the mode, then the mode is set in
accordance to the requested mode from the application.
.Pp
The
.Sy aclinherit
property does not apply to posix ACLs.
.It Sy acltype Ns = Ns Sy off Ns | Ns Sy noacl Ns | Ns Sy posixacl
Controls whether ACLs are enabled and if so what type of ACL to use.
.Bl -tag -width "posixacl"
.It Sy off
default, when a file system has the
.Sy acltype
property set to off then ACLs are disabled.
.It Sy noacl
an alias for
.Sy off
.It Sy posixacl
indicates posix ACLs should be used. Posix ACLs are specific to Linux and are
not functional on other platforms. Posix ACLs are stored as an extended
attribute and therefore will not overwrite any existing NFSv4 ACLs which
may be set.
.El
.Pp
To obtain the best performance when setting
.Sy posixacl
users are strongly encouraged to set the
.Sy xattr=sa
property. This will result in the posix ACL being stored more efficiently on
disk. But as a consequence of this all new extended attributes will only be
accessible from OpenZFS implementations which support the
.Sy xattr=sa
property. See the
.Sy xattr
property for more details.
.It Sy atime Ns = Ns Sy on Ns | Ns Sy off
Controls whether the access time for files is updated when they are read.
Turning this property off avoids producing write traffic when reading files and
can result in significant performance gains, though it might confuse mailers
and other similar utilities. The values
.Sy on
and
.Sy off
are equivalent to the
.Sy atime
and
.Sy noatime
mount options. The default value is
.Sy on .
See also
.Sy relatime
below.
.It Sy canmount Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy noauto
If this property is set to
.Sy off ,
the file system cannot be mounted, and is ignored by
.Nm zfs Cm mount Fl a .
Setting this property to
.Sy off
is similar to setting the
.Sy mountpoint
property to
.Sy none ,
except that the dataset still has a normal
.Sy mountpoint
property, which can be inherited.
Setting this property to
.Sy off
allows datasets to be used solely as a mechanism to inherit properties.
One example of setting
.Sy canmount Ns = Ns Sy off
is to have two datasets with the same
.Sy mountpoint ,
so that the children of both datasets appear in the same directory, but might
have different inherited characteristics.
.Pp
When set to
.Sy noauto ,
a dataset can only be mounted and unmounted explicitly.
The dataset is not mounted automatically when the dataset is created or
imported, nor is it mounted by the
.Nm zfs Cm mount Fl a
command or unmounted by the
.Nm zfs Cm unmount Fl a
command.
.Pp
This property is not inherited.
.It Xo
.Sy checksum Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy fletcher2 Ns | Ns
.Sy fletcher4 Ns | Ns Sy sha256 Ns | Ns Sy noparity Ns | Ns
.Sy sha512 Ns | Ns Sy skein Ns | Ns Sy edonr
.Xc
Controls the checksum used to verify data integrity.
The default value is
.Sy on ,
which automatically selects an appropriate algorithm
.Po currently,
.Sy fletcher4 ,
but this may change in future releases
.Pc .
The value
.Sy off
disables integrity checking on user data.
The value
.Sy noparity
not only disables integrity but also disables maintaining parity for user data.
This setting is used internally by a dump device residing on a RAID-Z pool and
should not be used by any other dataset.
Disabling checksums is
.Sy NOT
a recommended practice.
.Pp
The
.Sy sha512 ,
.Sy skein ,
and
.Sy edonr
checksum algorithms require enabling the appropriate features on the pool.
Please see
.Xr zpool-features 5
for more information on these algorithms.
.Pp
Changing this property affects only newly-written data.
.It Xo
.Sy compression Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy gzip Ns | Ns
.Sy gzip- Ns Em N Ns | Ns Sy lz4 Ns | Ns Sy lzjb Ns | Ns Sy zle
.Xc
Controls the compression algorithm used for this dataset.
.Pp
Setting compression to
.Sy on
indicates that the current default compression algorithm should be used.
The default balances compression and decompression speed, with compression ratio
and is expected to work well on a wide variety of workloads.
Unlike all other settings for this property,
.Sy on
does not select a fixed compression type.
As new compression algorithms are added to ZFS and enabled on a pool, the
default compression algorithm may change.
The current default compression algorithm is either
.Sy lzjb
or, if the
.Sy lz4_compress
feature is enabled,
.Sy lz4 .
.Pp
The
.Sy lz4
compression algorithm is a high-performance replacement for the
.Sy lzjb
algorithm.
It features significantly faster compression and decompression, as well as a
moderately higher compression ratio than
.Sy lzjb ,
but can only be used on pools with the
.Sy lz4_compress
feature set to
.Sy enabled .
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy lz4_compress
feature.
.Pp
The
.Sy lzjb
compression algorithm is optimized for performance while providing decent data
compression.
.Pp
The
.Sy gzip
compression algorithm uses the same compression as the
.Xr gzip 1
command.
You can specify the
.Sy gzip
level by using the value
.Sy gzip- Ns Em N ,
where
.Em N
is an integer from 1
.Pq fastest
to 9
.Pq best compression ratio .
Currently,
.Sy gzip
is equivalent to
.Sy gzip-6
.Po which is also the default for
.Xr gzip 1
.Pc .
.Pp
The
.Sy zle
compression algorithm compresses runs of zeros.
.Pp
This property can also be referred to by its shortened column name
.Sy compress .
Changing this property affects only newly-written data.
.It Xo
.Sy context Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for all files in the file system under
a mount point for that file system. See
.Xr selinux 8
for more information.
.It Xo
.Sy fscontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for the file system file system being
mounted. See
.Xr selinux 8
for more information.
.It Xo
.Sy defcontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux default context for unlabeled files. See
.Xr selinux 8
for more information.
.It Xo
.Sy rootcontext Ns = Ns Sy none Ns | Ns
.Em SELinux_User:SElinux_Role:Selinux_Type:Sensitivity_Level
.Xc
This flag sets the SELinux context for the root inode of the file system. See
.Xr selinux 8
for more information.
.It Sy copies Ns = Ns Sy 1 Ns | Ns Sy 2 Ns | Ns Sy 3
Controls the number of copies of data stored for this dataset.
These copies are in addition to any redundancy provided by the pool, for
example, mirroring or RAID-Z.
The copies are stored on different disks, if possible.
The space used by multiple copies is charged to the associated file and dataset,
changing the
.Sy used
property and counting against quotas and reservations.
.Pp
Changing this property only affects newly-written data.
Therefore, set this property at file system creation time by using the
.Fl o Sy copies Ns = Ns Ar N
option.
.Pp
Remember that ZFS will not import a pool with a missing top-level vdev. Do
.Sy NOT
create, for example a two-disk striped pool and set
.Sy copies=2
on some datasets thinking you have setup redundancy for them. When a disk
fails you will not be able to import the pool and will have lost all of your
data.
.It Sy devices Ns = Ns Sy on Ns | Ns Sy off
Controls whether device nodes can be opened on this file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy dev
and
.Sy nodev
mount options.
.It Xo
.Sy dnodesize Ns = Ns Sy legacy Ns | Ns Sy auto Ns | Ns Sy 1k Ns | Ns
.Sy 2k Ns | Ns Sy 4k Ns | Ns Sy 8k Ns | Ns Sy 16k
.Xc
Specifies a compatibility mode or literal value for the size of dnodes in the
file system. The default value is
.Sy legacy .
Setting this property to a value other than
.Sy legacy
requires the large_dnode pool feature to be enabled.
.Pp
Consider setting
.Sy dnodesize
to
.Sy auto
if the dataset uses the
.Sy xattr=sa
property setting and the workload makes heavy use of extended attributes. This
may be applicable to SELinux-enabled systems, Lustre servers, and Samba
servers, for example. Literal values are supported for cases where the optimal
size is known in advance and for performance testing.
.Pp
Leave
.Sy dnodesize
set to
.Sy legacy
if you need to receive a send stream of this dataset on a pool that doesn't
enable the large_dnode feature, or if you need to import this pool on a system
that doesn't support the large_dnode feature.
.Pp
This property can also be referred to by its shortened column name,
.Sy dnsize .
.It Xo
.Sy encryption Ns = Ns Sy off Ns | Ns Sy on Ns | Ns Sy aes-128-ccm Ns | Ns
.Sy aes-192-ccm Ns | Ns Sy aes-256-ccm Ns | Ns Sy aes-128-gcm Ns | Ns
.Sy aes-192-gcm Ns | Ns Sy aes-256-gcm
.Xc
Controls the encryption cipher suite (block cipher, key length, and mode) used
for this dataset. Requires the
.Sy encryption
feature to be enabled on the pool.
Requires a
.Sy keyformat
to be set at dataset creation time.
.Pp
Selecting
.Sy encryption Ns = Ns Sy on
when creating a dataset indicates that the default encryption suite will be
selected, which is currently
.Sy aes-256-ccm .
In order to provide consistent data protection, encryption must be specified at
dataset creation time and it cannot be changed afterwards.
.Pp
For more details and caveats about encryption see the
.Sy Encryption
section.
.It Sy keyformat Ns = Ns Sy raw Ns | Ns Sy hex Ns | Ns Sy passphrase
Controls what format the user's encryption key will be provided as. This
property is only set when the dataset is encrypted.
.Pp
Raw keys and hex keys must be 32 bytes long (regardless of the chosen
encryption suite) and must be randomly generated. A raw key can be generated
with the following command:
.Bd -literal
# dd if=/dev/urandom of=/path/to/output/key bs=32 count=1
.Ed
.Pp
Passphrases must be between 8 and 512 bytes long and will be processed through
PBKDF2 before being used (see the
.Sy pbkdf2iters
property). Even though the
encryption suite cannot be changed after dataset creation, the keyformat can be
with
.Nm zfs Cm change-key .
.It Xo
.Sy keylocation Ns = Ns Sy prompt Ns | Ns Sy file:// Ns Em </absolute/file/path>
.Xc
Controls where the user's encryption key will be loaded from by default for
commands such as
.Nm zfs Cm load-key
and
.Nm zfs Cm mount Cm -l . This property is
only set for encrypted datasets which are encryption roots. If unspecified, the
default is
.Sy prompt.
.Pp
Even though the encryption suite cannot be changed after dataset creation, the
keylocation can be with either
.Nm zfs Cm set
or
.Nm zfs Cm change-key .
If
.Sy prompt
is selected ZFS will ask for the key at the command prompt when it is required
to access the encrypted data (see
.Nm zfs Cm load-key
for details). This setting will also allow the key to be passed in via STDIN,
but users should be careful not to place keys which should be kept secret on
the command line. If a file URI is selected, the key will be loaded from the
specified absolute file path.
.It Sy pbkdf2iters Ns = Ns Ar iterations
Controls the number of PBKDF2 iterations that a
.Sy passphrase
encryption key should be run through when processing it into an encryption key.
This property is only defined when encryption is enabled and a keyformat of
.Sy passphrase
is selected. The goal of PBKDF2 is to significantly increase the
computational difficulty needed to brute force a user's passphrase. This is
accomplished by forcing the attacker to run each passphrase through a
computationally expensive hashing function many times before they arrive at the
resulting key. A user who actually knows the passphrase will only have to pay
this cost once. As CPUs become better at processing, this number should be
raised to ensure that a brute force attack is still not possible. The current
default is
.Sy 350000
and the minimum is
.Sy 100000 .
This property may be changed with
.Nm zfs Cm change-key .
.It Sy exec Ns = Ns Sy on Ns | Ns Sy off
Controls whether processes can be executed from within this file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy exec
and
.Sy noexec
mount options.
.It Sy filesystem_limit Ns = Ns Em count Ns | Ns Sy none
Limits the number of filesystems and volumes that can exist under this point in
the dataset tree.
The limit is not enforced if the user is allowed to change the limit.
Setting a
.Sy filesystem_limit
to
.Sy on
a descendent of a filesystem that already has a
.Sy filesystem_limit
does not override the ancestor's
.Sy filesystem_limit ,
but rather imposes an additional limit.
This feature must be enabled to be used
.Po see
.Xr zpool-features 5
.Pc .
.It Sy mountpoint Ns = Ns Pa path Ns | Ns Sy none Ns | Ns Sy legacy
Controls the mount point used for this file system.
See the
.Sx Mount Points
section for more information on how this property is used.
.Pp
When the
.Sy mountpoint
property is changed for a file system, the file system and any children that
inherit the mount point are unmounted.
If the new value is
.Sy legacy ,
then they remain unmounted.
Otherwise, they are automatically remounted in the new location if the property
was previously
.Sy legacy
or
.Sy none ,
or if they were mounted before the property was changed.
In addition, any shared file systems are unshared and shared in the new
location.
.It Sy nbmand Ns = Ns Sy on Ns | Ns Sy off
Controls whether the file system should be mounted with
.Sy nbmand
.Pq Non Blocking mandatory locks .
This is used for SMB clients.
Changes to this property only take effect when the file system is umounted and
remounted.
See
.Xr mount 8
for more information on
.Sy nbmand
mounts. This property is not used on Linux.
.It Sy overlay Ns = Ns Sy off Ns | Ns Sy on
Allow mounting on a busy directory or a directory which already contains
files or directories. This is the default mount behavior for Linux file systems.
For consistency with OpenZFS on other platforms overlay mounts are
.Sy off
by default. Set to
.Sy on
to enable overlay mounts.
.It Sy primarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
Controls what is cached in the primary cache
.Pq ARC .
If this property is set to
.Sy all ,
then both user data and metadata is cached.
If this property is set to
.Sy none ,
then neither user data nor metadata is cached.
If this property is set to
.Sy metadata ,
then only metadata is cached.
The default value is
.Sy all .
.It Sy quota Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space a dataset and its descendents can consume.
This property enforces a hard limit on the amount of space used.
This includes all space consumed by descendents, including file systems and
snapshots.
Setting a quota on a descendent of a dataset that already has a quota does not
override the ancestor's quota, but rather imposes an additional limit.
.Pp
Quotas cannot be set on volumes, as the
.Sy volsize
property acts as an implicit quota.
.It Sy snapshot_limit Ns = Ns Em count Ns | Ns Sy none
Limits the number of snapshots that can be created on a dataset and its
descendents.
Setting a
.Sy snapshot_limit
on a descendent of a dataset that already has a
.Sy snapshot_limit
does not override the ancestor's
.Sy snapshot_limit ,
but rather imposes an additional limit.
The limit is not enforced if the user is allowed to change the limit.
For example, this means that recursive snapshots taken from the global zone are
counted against each delegated dataset within a zone.
This feature must be enabled to be used
.Po see
.Xr zpool-features 5
.Pc .
.It Sy userquota@ Ns Em user Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space consumed by the specified user.
User space consumption is identified by the
.Sy userspace@ Ns Em user
property.
.Pp
Enforcement of user quotas may be delayed by several seconds.
This delay means that a user might exceed their quota before the system notices
that they are over quota and begins to refuse additional writes with the
.Er EDQUOT
error message.
See the
.Nm zfs Cm userspace
subcommand for more information.
.Pp
Unprivileged users can only access their own groups' space usage.
The root user, or a user who has been granted the
.Sy userquota
privilege with
.Nm zfs Cm allow ,
can get and set everyone's quota.
.Pp
This property is not available on volumes, on file systems before version 4, or
on pools before version 15.
The
.Sy userquota@ Ns Em ...
properties are not displayed by
.Nm zfs Cm get Sy all .
The user's name must be appended after the
.Sy @
symbol, using one of the following forms:
.Bl -bullet
.It
.Em POSIX name
.Po for example,
.Sy joe
.Pc
.It
.Em POSIX numeric ID
.Po for example,
.Sy 789
.Pc
.It
.Em SID name
.Po for example,
.Sy joe.smith@mydomain
.Pc
.It
.Em SID numeric ID
.Po for example,
.Sy S-1-123-456-789
.Pc
.El
.Pp
Files created on Linux always have POSIX owners.
.It Sy userobjquota@ Ns Em user Ns = Ns Em size Ns | Ns Sy none
The
.Sy userobjquota
is similar to
.Sy userquota
but it limits the number of objects a user can create. Please refer to
.Sy userobjused
for more information about how objects are counted.
.It Sy groupquota@ Ns Em group Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space consumed by the specified group.
Group space consumption is identified by the
.Sy groupused@ Ns Em group
property.
.Pp
Unprivileged users can access only their own groups' space usage.
The root user, or a user who has been granted the
.Sy groupquota
privilege with
.Nm zfs Cm allow ,
can get and set all groups' quotas.
.It Sy groupobjquota@ Ns Em group Ns = Ns Em size Ns | Ns Sy none
The
.Sy groupobjquota
is similar to
.Sy groupquota
but it limits number of objects a group can consume. Please refer to
.Sy userobjused
for more information about how objects are counted.
.It Sy readonly Ns = Ns Sy on Ns | Ns Sy off
Controls whether this dataset can be modified.
The default value is
.Sy off .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy ro
and
.Sy rw
mount options.
.Pp
This property can also be referred to by its shortened column name,
.Sy rdonly .
.It Sy recordsize Ns = Ns Em size
Specifies a suggested block size for files in the file system.
This property is designed solely for use with database workloads that access
files in fixed-size records.
ZFS automatically tunes block sizes according to internal algorithms optimized
for typical access patterns.
.Pp
For databases that create very large files but access them in small random
chunks, these algorithms may be suboptimal.
Specifying a
.Sy recordsize
greater than or equal to the record size of the database can result in
significant performance gains.
Use of this property for general purpose file systems is strongly discouraged,
and may adversely affect performance.
.Pp
The size specified must be a power of two greater than or equal to 512 and less
than or equal to 128 Kbytes.
If the
.Sy large_blocks
feature is enabled on the pool, the size may be up to 1 Mbyte.
See
.Xr zpool-features 5
for details on ZFS feature flags.
.Pp
Changing the file system's
.Sy recordsize
affects only files created afterward; existing files are unaffected.
.Pp
This property can also be referred to by its shortened column name,
.Sy recsize .
.It Sy redundant_metadata Ns = Ns Sy all Ns | Ns Sy most
Controls what types of metadata are stored redundantly.
ZFS stores an extra copy of metadata, so that if a single block is corrupted,
the amount of user data lost is limited.
This extra copy is in addition to any redundancy provided at the pool level
.Pq e.g. by mirroring or RAID-Z ,
and is in addition to an extra copy specified by the
.Sy copies
property
.Pq up to a total of 3 copies .
For example if the pool is mirrored,
.Sy copies Ns = Ns 2 ,
and
.Sy redundant_metadata Ns = Ns Sy most ,
then ZFS stores 6 copies of most metadata, and 4 copies of data and some
metadata.
.Pp
When set to
.Sy all ,
ZFS stores an extra copy of all metadata.
If a single on-disk block is corrupt, at worst a single block of user data
.Po which is
.Sy recordsize
bytes long
.Pc
can be lost.
.Pp
When set to
.Sy most ,
ZFS stores an extra copy of most types of metadata.
This can improve performance of random writes, because less metadata must be
written.
In practice, at worst about 100 blocks
.Po of
.Sy recordsize
bytes each
.Pc
of user data can be lost if a single on-disk block is corrupt.
The exact behavior of which metadata blocks are stored redundantly may change in
future releases.
.Pp
The default value is
.Sy all .
.It Sy refquota Ns = Ns Em size Ns | Ns Sy none
Limits the amount of space a dataset can consume.
This property enforces a hard limit on the amount of space used.
This hard limit does not include space used by descendents, including file
systems and snapshots.
.It Sy refreservation Ns = Ns Em size Ns | Ns Sy none
The minimum amount of space guaranteed to a dataset, not including its
descendents.
When the amount of space used is below this value, the dataset is treated as if
it were taking up the amount of space specified by
.Sy refreservation .
The
.Sy refreservation
reservation is accounted for in the parent datasets' space used, and counts
against the parent datasets' quotas and reservations.
.Pp
If
.Sy refreservation
is set, a snapshot is only allowed if there is enough free pool space outside of
this reservation to accommodate the current number of
.Qq referenced
bytes in the dataset.
.Pp
This property can also be referred to by its shortened column name,
.Sy refreserv .
.It Sy relatime Ns = Ns Sy on Ns | Ns Sy off
Controls the manner in which the access time is updated when
.Sy atime=on
is set. Turning this property on causes the access time to be updated relative
to the modify or change time. Access time is only updated if the previous
access time was earlier than the current modify or change time or if the
existing access time hasn't been updated within the past 24 hours. The default
value is
.Sy off .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy relatime
and
.Sy norelatime
mount options.
.It Sy reservation Ns = Ns Em size Ns | Ns Sy none
The minimum amount of space guaranteed to a dataset and its descendants.
When the amount of space used is below this value, the dataset is treated as if
it were taking up the amount of space specified by its reservation.
Reservations are accounted for in the parent datasets' space used, and count
against the parent datasets' quotas and reservations.
.Pp
This property can also be referred to by its shortened column name,
.Sy reserv .
.It Sy secondarycache Ns = Ns Sy all Ns | Ns Sy none Ns | Ns Sy metadata
Controls what is cached in the secondary cache
.Pq L2ARC .
If this property is set to
.Sy all ,
then both user data and metadata is cached.
If this property is set to
.Sy none ,
then neither user data nor metadata is cached.
If this property is set to
.Sy metadata ,
then only metadata is cached.
The default value is
.Sy all .
.It Sy setuid Ns = Ns Sy on Ns | Ns Sy off
Controls whether the setuid bit is respected for the file system.
The default value is
.Sy on .
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy suid
and
.Sy nosuid
mount options.
.It Sy sharesmb Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Em opts
Controls whether the file system is shared by using
.Sy Samba USERSHARES
and what options are to be used. Otherwise, the file system is automatically
shared and unshared with the
.Nm zfs Cm share
and
.Nm zfs Cm unshare
commands. If the property is set to on, the
.Xr net 8
command is invoked to create a
.Sy USERSHARE .
.Pp
Because SMB shares requires a resource name, a unique resource name is
constructed from the dataset name. The constructed name is a copy of the
dataset name except that the characters in the dataset name, which would be
invalid in the resource name, are replaced with underscore (_) characters.
Linux does not currently support additional options which might be available
on Solaris.
.Pp
If the
.Sy sharesmb
property is set to
.Sy off ,
the file systems are unshared.
.Pp
The share is created with the ACL (Access Control List) "Everyone:F" ("F"
stands for "full permissions", ie. read and write permissions) and no guest
access (which means Samba must be able to authenticate a real user, system
passwd/shadow, LDAP or smbpasswd based) by default. This means that any
additional access control (disallow specific user specific access etc) must
be done on the underlying file system.
.It Sy sharenfs Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Em opts
Controls whether the file system is shared via NFS, and what options are to be
used.
A file system with a
.Sy sharenfs
property of
.Sy off
is managed with the
.Xr exportfs 8
command and entries in the
.Em /etc/exports
file.
Otherwise, the file system is automatically shared and unshared with the
.Nm zfs Cm share
and
.Nm zfs Cm unshare
commands.
If the property is set to
.Sy on ,
the dataset is shared using the default options:
.Pp
.Em sec=sys,rw,crossmnt,no_subtree_check,no_root_squash
.Pp
See
.Xr exports 5
for the meaning of the default options. Otherwise, the
.Xr exportfs 8
command is invoked with options equivalent to the contents of this property.
.Pp
When the
.Sy sharenfs
property is changed for a dataset, the dataset and any children inheriting the
property are re-shared with the new options, only if the property was previously
.Sy off ,
or if they were shared before the property was changed.
If the new property is
.Sy off ,
the file systems are unshared.
.It Sy logbias Ns = Ns Sy latency Ns | Ns Sy throughput
Provide a hint to ZFS about handling of synchronous requests in this dataset.
If
.Sy logbias
is set to
.Sy latency
.Pq the default ,
ZFS will use pool log devices
.Pq if configured
to handle the requests at low latency.
If
.Sy logbias
is set to
.Sy throughput ,
ZFS will not use configured pool log devices.
ZFS will instead optimize synchronous operations for global pool throughput and
efficient use of resources.
.It Sy snapdev Ns = Ns Sy hidden Ns | Ns Sy visible
Controls whether the volume snapshot devices under
.Em /dev/zvol/<pool>
are hidden or visible. The default value is
.Sy hidden .
.It Sy snapdir Ns = Ns Sy hidden Ns | Ns Sy visible
Controls whether the
.Pa .zfs
directory is hidden or visible in the root of the file system as discussed in
the
.Sx Snapshots
section.
The default value is
.Sy hidden .
.It Sy sync Ns = Ns Sy standard Ns | Ns Sy always Ns | Ns Sy disabled
Controls the behavior of synchronous requests
.Pq e.g. fsync, O_DSYNC .
.Sy standard
is the
.Tn POSIX
specified behavior of ensuring all synchronous requests are written to stable
storage and all devices are flushed to ensure data is not cached by device
controllers
.Pq this is the default .
.Sy always
causes every file system transaction to be written and flushed before its
system call returns.
This has a large performance penalty.
.Sy disabled
disables synchronous requests.
File system transactions are only committed to stable storage periodically.
This option will give the highest performance.
However, it is very dangerous as ZFS would be ignoring the synchronous
transaction demands of applications such as databases or NFS.
Administrators should only use this option when the risks are understood.
.It Sy version Ns = Ns Em N Ns | Ns Sy current
The on-disk version of this file system, which is independent of the pool
version.
This property can only be set to later supported versions.
See the
.Nm zfs Cm upgrade
command.
.It Sy volsize Ns = Ns Em size
For volumes, specifies the logical size of the volume.
By default, creating a volume establishes a reservation of equal size.
For storage pools with a version number of 9 or higher, a
.Sy refreservation
is set instead.
Any changes to
.Sy volsize
are reflected in an equivalent change to the reservation
.Po or
.Sy refreservation
.Pc .
The
.Sy volsize
can only be set to a multiple of
.Sy volblocksize ,
and cannot be zero.
.Pp
The reservation is kept equal to the volume's logical size to prevent unexpected
behavior for consumers.
Without the reservation, the volume could run out of space, resulting in
undefined behavior or data corruption, depending on how the volume is used.
These effects can also occur when the volume size is changed while it is in use
.Pq particularly when shrinking the size .
Extreme care should be used when adjusting the volume size.
.Pp
Though not recommended, a
.Qq sparse volume
.Po also known as
.Qq thin provisioning
.Pc
can be created by specifying the
.Fl s
option to the
.Nm zfs Cm create Fl V
command, or by changing the reservation after the volume has been created.
A
.Qq sparse volume
is a volume where the reservation is less then the volume size.
Consequently, writes to a sparse volume can fail with
.Er ENOSPC
when the pool is low on space.
For a sparse volume, changes to
.Sy volsize
are not reflected in the reservation.
.It Sy volmode Ns = Ns Cm default | full | geom | dev | none
This property specifies how volumes should be exposed to the OS.
Setting it to
.Sy full
exposes volumes as fully fledged block devices, providing maximal
functionality. The value
.Sy geom
is just an alias for
.Sy full
and is kept for compatibility.
Setting it to
.Sy dev
hides its partitions.
Volumes with property set to
.Sy none
are not exposed outside ZFS, but can be snapshoted, cloned, replicated, etc,
that can be suitable for backup purposes.
Value
.Sy default
means that volumes exposition is controlled by system-wide tunable
.Va zvol_volmode ,
where
.Sy full ,
.Sy dev
and
.Sy none
are encoded as 1, 2 and 3 respectively.
The default values is
.Sy full .
.It Sy vscan Ns = Ns Sy on Ns | Ns Sy off
Controls whether regular files should be scanned for viruses when a file is
opened and closed.
In addition to enabling this property, the virus scan service must also be
enabled for virus scanning to occur.
The default value is
.Sy off .
This property is not used on Linux.
.It Sy xattr Ns = Ns Sy on Ns | Ns Sy off Ns | Ns Sy sa
Controls whether extended attributes are enabled for this file system. Two
styles of extended attributes are supported either directory based or system
attribute based.
.Pp
The default value of
.Sy on
enables directory based extended attributes. This style of extended attribute
imposes no practical limit on either the size or number of attributes which
can be set on a file. Although under Linux the
.Xr getxattr 2
and
.Xr setxattr 2
system calls limit the maximum size to 64K. This is the most compatible
style of extended attribute and is supported by all OpenZFS implementations.
.Pp
System attribute based xattrs can be enabled by setting the value to
.Sy sa .
The key advantage of this type of xattr is improved performance. Storing
extended attributes as system attributes significantly decreases the amount of
disk IO required. Up to 64K of data may be stored per-file in the space
reserved for system attributes. If there is not enough space available for
an extended attribute then it will be automatically written as a directory
based xattr. System attribute based extended attributes are not accessible
on platforms which do not support the
.Sy xattr=sa
feature.
.Pp
The use of system attribute based xattrs is strongly encouraged for users of
SELinux or posix ACLs. Both of these features heavily rely of extended
attributes and benefit significantly from the reduced access time.
.Pp
The values
.Sy on
and
.Sy off
are equivalent to the
.Sy xattr
and
.Sy noxattr
mount options.
.It Sy zoned Ns = Ns Sy on Ns | Ns Sy off
Controls whether the dataset is managed from a non-global zone. Zones are a
Solaris feature and are not relevant on Linux. The default value is
.Sy off .
.El
.Pp
The following three properties cannot be changed after the file system is
created, and therefore, should be set when the file system is created.
If the properties are not set with the
.Nm zfs Cm create
or
.Nm zpool Cm create
commands, these properties are inherited from the parent dataset.
If the parent dataset lacks these properties due to having been created prior to
these features being supported, the new file system will have the default values
for these properties.
.Bl -tag -width ""
.It Xo
.Sy casesensitivity Ns = Ns Sy sensitive Ns | Ns
.Sy insensitive Ns | Ns Sy mixed
.Xc
Indicates whether the file name matching algorithm used by the file system
should be case-sensitive, case-insensitive, or allow a combination of both
styles of matching.
The default value for the
.Sy casesensitivity
property is
.Sy sensitive .
Traditionally,
.Ux
and
.Tn POSIX
file systems have case-sensitive file names.
.Pp
The
.Sy mixed
value for the
.Sy casesensitivity
property indicates that the file system can support requests for both
case-sensitive and case-insensitive matching behavior.
Currently, case-insensitive matching behavior on a file system that supports
mixed behavior is limited to the SMB server product.
For more information about the
.Sy mixed
value behavior, see the "ZFS Administration Guide".
.It Xo
.Sy normalization Ns = Ns Sy none Ns | Ns Sy formC Ns | Ns
.Sy formD Ns | Ns Sy formKC Ns | Ns Sy formKD
.Xc
Indicates whether the file system should perform a
.Sy unicode
normalization of file names whenever two file names are compared, and which
normalization algorithm should be used.
File names are always stored unmodified, names are normalized as part of any
comparison process.
If this property is set to a legal value other than
.Sy none ,
and the
.Sy utf8only
property was left unspecified, the
.Sy utf8only
property is automatically set to
.Sy on .
The default value of the
.Sy normalization
property is
.Sy none .
This property cannot be changed after the file system is created.
.It Sy utf8only Ns = Ns Sy on Ns | Ns Sy off
Indicates whether the file system should reject file names that include
characters that are not present in the
.Sy UTF-8
character code set.
If this property is explicitly set to
.Sy off ,
the normalization property must either not be explicitly set or be set to
.Sy none .
The default value for the
.Sy utf8only
property is
.Sy off .
This property cannot be changed after the file system is created.
.El
.Pp
The
.Sy casesensitivity ,
.Sy normalization ,
and
.Sy utf8only
properties are also new permissions that can be assigned to non-privileged users
by using the ZFS delegated administration feature.
.Ss "Temporary Mount Point Properties"
When a file system is mounted, either through
.Xr mount 8
for legacy mounts or the
.Nm zfs Cm mount
command for normal file systems, its mount options are set according to its
properties.
The correlation between properties and mount options is as follows:
.Bd -literal
    PROPERTY                MOUNT OPTION
    atime                   atime/noatime
    canmount                auto/noauto
    devices                 dev/nodev
    exec                    exec/noexec
    readonly                ro/rw
    relatime                relatime/norelatime
    setuid                  suid/nosuid
    xattr                   xattr/noxattr
.Ed
.Pp
In addition, these options can be set on a per-mount basis using the
.Fl o
option, without affecting the property that is stored on disk.
The values specified on the command line override the values stored in the
dataset.
The
.Sy nosuid
option is an alias for
.Sy nodevices Ns \&, Ns Sy nosetuid .
These properties are reported as
.Qq temporary
by the
.Nm zfs Cm get
command.
If the properties are changed while the dataset is mounted, the new setting
overrides any temporary settings.
.Ss "User Properties"
In addition to the standard native properties, ZFS supports arbitrary user
properties.
User properties have no effect on ZFS behavior, but applications or
administrators can use them to annotate datasets
.Pq file systems, volumes, and snapshots .
.Pp
User property names must contain a colon
.Pq Qq Sy \&:
character to distinguish them from native properties.
They may contain lowercase letters, numbers, and the following punctuation
characters: colon
.Pq Qq Sy \&: ,
dash
.Pq Qq Sy - ,
period
.Pq Qq Sy \&. ,
and underscore
.Pq Qq Sy _ .
The expected convention is that the property name is divided into two portions
such as
.Em module Ns \&: Ns Em property ,
but this namespace is not enforced by ZFS.
User property names can be at most 256 characters, and cannot begin with a dash
.Pq Qq Sy - .
.Pp
When making programmatic use of user properties, it is strongly suggested to use
a reversed
.Sy DNS
domain name for the
.Em module
component of property names to reduce the chance that two
independently-developed packages use the same property name for different
purposes.
.Pp
The values of user properties are arbitrary strings, are always inherited, and
are never validated.
All of the commands that operate on properties
.Po Nm zfs Cm list ,
.Nm zfs Cm get ,
.Nm zfs Cm set ,
and so forth
.Pc
can be used to manipulate both native properties and user properties.
Use the
.Nm zfs Cm inherit
command to clear a user property.
If the property is not defined in any parent dataset, it is removed entirely.
Property values are limited to 8192 bytes.
.Ss ZFS Volumes as Swap
ZFS volumes may be used as swap devices. After creating the volume with the
.Nm zfs Cm create Fl V
command set up and enable the swap area using the
.Xr mkswap 8
and
.Xr swapon 8
commands. Do not swap to a file on a ZFS file system. A ZFS swap file
configuration is not supported.
.Ss Encryption
Enabling the
.Sy encryption
feature allows for the creation of encrypted filesystems and volumes.
.Nm
will encrypt all user data including file and zvol data, file attributes,
ACLs, permission bits, directory listings, FUID mappings, and userused /
groupused data.
.Nm
will not encrypt metadata related to the pool structure, including dataset
names, dataset hierarchy, file size, file holes, and dedup tables. Key rotation
is managed internally by the  kernel module and changing the user's key does not
require re-encrypting the entire dataset. Datasets can be scrubbed, resilvered,
renamed, and deleted without the encryption keys being loaded (see the
.Nm zfs Cm load-key
subcommand for more info on key loading).
.Pp
Creating an encrypted dataset requires specifying the
.Sy encryption
and
.Sy keyformat
properties at creation time, along with an optional
.Sy keylocation
and
.Sy pbkdf2iters .
After entering an encryption key, the
created dataset will become an encryption root. Any descendant datasets will
inherit their encryption key from the encryption root by default, meaning that
loading, unloading, or changing the key for the encryption root will implicitly
do the same for all inheriting datasets. If this inheritance is not desired,
simply supply a
.Sy keyformat
when creating the child dataset or use
.Nm zfs Cm change-key
to break an existing relationship, creating a new encryption root on the child.
Note that the child's
.Sy keyformat
may match that of the parent while still creating a new encryption root, and
that changing the
.Sy encryption
property alone does not create a new encryption root; this would simply use a
different cipher suite with the same key as its encryption root. The one
exception is that clones will always use their origin's encryption key.
As a result of this exception, some encryption-related properties (namely
.Sy keystatus ,
.Sy keyformat ,
.Sy keylocation ,
and
.Sy pbkdf2iters )
do not inherit like other ZFS properties and instead use the value determined
by their encryption root. Encryption root inheritance can be tracked via the
read-only
.Sy encryptionroot
property.
.Pp
Encryption changes the behavior of a few
.Nm
operations. Encryption is applied after compression so compression ratios are
preserved. Normally checksums in ZFS are 256 bits long, but for encrypted data
the checksum is 128 bits of the user-chosen checksum and 128 bits of MAC from
the encryption suite, which provides additional protection against maliciously
altered data. Deduplication is still possible with encryption enabled but for
security, datasets will only dedup against themselves, their snapshots, and
their clones.
.Pp
There are a few limitations on encrypted datasets. Encrypted data cannot be
embedded via the
.Sy embedded_data
feature. Encrypted datasets may not have
.Sy copies Ns = Ns Em 3
since the implementation stores some encryption metadata where the third copy
would normally be. Since compression is applied before encryption datasets may
be vulnerable to a CRIME-like attack if applications accessing the data allow
for it. Deduplication with encryption will leak information about which blocks
are equivalent in a dataset and will incur an extra CPU cost per block written.
.Sh SUBCOMMANDS
All subcommands that modify state are logged persistently to the pool in their
original form.
.Bl -tag -width ""
.It Nm Fl ?
Displays a help message.
.It Xo
.Nm
.Cm create
.Op Fl p
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Ar filesystem
.Xc
Creates a new ZFS file system.
The file system is automatically mounted according to the
.Sy mountpoint
property inherited from the parent.
.Bl -tag -width "-o"
.It Fl o Ar property Ns = Ns Ar value
Sets the specified property as if the command
.Nm zfs Cm set Ar property Ns = Ns Ar value
was invoked at the same time the dataset was created.
Any editable ZFS property can also be set at creation time.
Multiple
.Fl o
options can be specified.
An error results if the same property is specified in multiple
.Fl o
options.
.It Fl p
Creates all the non-existing parent datasets.
Datasets created in this manner are automatically mounted according to the
.Sy mountpoint
property inherited from their parent.
Any property specified on the command line using the
.Fl o
option is ignored.
If the target filesystem already exists, the operation completes successfully.
.El
.It Xo
.Nm
.Cm create
.Op Fl ps
.Op Fl b Ar blocksize
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Fl V Ar size Ar volume
.Xc
Creates a volume of the given size.
The volume is exported as a block device in
.Pa /dev/zvol/path ,
where
.Em path
is the name of the volume in the ZFS namespace.
The size represents the logical size as exported by the device.
By default, a reservation of equal size is created.
.Pp
.Ar size
is automatically rounded up to the nearest 128 Kbytes to ensure that the volume
has an integral number of blocks regardless of
.Sy blocksize .
.Bl -tag -width "-b"
.It Fl b Ar blocksize
Equivalent to
.Fl o Sy volblocksize Ns = Ns Ar blocksize .
If this option is specified in conjunction with
.Fl o Sy volblocksize ,
the resulting behavior is undefined.
.It Fl o Ar property Ns = Ns Ar value
Sets the specified property as if the
.Nm zfs Cm set Ar property Ns = Ns Ar value
command was invoked at the same time the dataset was created.
Any editable ZFS property can also be set at creation time.
Multiple
.Fl o
options can be specified.
An error results if the same property is specified in multiple
.Fl o
options.
.It Fl p
Creates all the non-existing parent datasets.
Datasets created in this manner are automatically mounted according to the
.Sy mountpoint
property inherited from their parent.
Any property specified on the command line using the
.Fl o
option is ignored.
If the target filesystem already exists, the operation completes successfully.
.It Fl s
Creates a sparse volume with no reservation.
See
.Sy volsize
in the
.Sx Native Properties
section for more information about sparse volumes.
.El
.It Xo
.Nm
.Cm destroy
.Op Fl Rfnprv
.Ar filesystem Ns | Ns Ar volume
.Xc
Destroys the given dataset.
By default, the command unshares any file systems that are currently shared,
unmounts any file systems that are currently mounted, and refuses to destroy a
dataset that has active dependents
.Pq children or clones .
.Bl -tag -width "-R"
.It Fl R
Recursively destroy all dependents, including cloned file systems outside the
target hierarchy.
.It Fl f
Force an unmount of any file systems using the
.Nm unmount Fl f
command.
This option has no effect on non-file systems or unmounted file systems.
.It Fl n
Do a dry-run
.Pq Qq No-op
deletion.
No data will be deleted.
This is useful in conjunction with the
.Fl v
or
.Fl p
flags to determine what data would be deleted.
.It Fl p
Print machine-parsable verbose information about the deleted data.
.It Fl r
Recursively destroy all children.
.It Fl v
Print verbose information about the deleted data.
.El
.Pp
Extreme care should be taken when applying either the
.Fl r
or the
.Fl R
options, as they can destroy large portions of a pool and cause unexpected
behavior for mounted file systems in use.
.It Xo
.Nm
.Cm destroy
.Op Fl Rdnprv
.Ar filesystem Ns | Ns Ar volume Ns @ Ns Ar snap Ns
.Oo % Ns Ar snap Ns Oo , Ns Ar snap Ns Oo % Ns Ar snap Oc Oc Oc Ns ...
.Xc
The given snapshots are destroyed immediately if and only if the
.Nm zfs Cm destroy
command without the
.Fl d
option would have destroyed it.
Such immediate destruction would occur, for example, if the snapshot had no
clones and the user-initiated reference count were zero.
.Pp
If a snapshot does not qualify for immediate destruction, it is marked for
deferred deletion.
In this state, it exists as a usable, visible snapshot until both of the
preconditions listed above are met, at which point it is destroyed.
.Pp
An inclusive range of snapshots may be specified by separating the first and
last snapshots with a percent sign.
The first and/or last snapshots may be left blank, in which case the
filesystem's oldest or newest snapshot will be implied.
.Pp
Multiple snapshots
.Pq or ranges of snapshots
of the same filesystem or volume may be specified in a comma-separated list of
snapshots.
Only the snapshot's short name
.Po the part after the
.Sy @
.Pc
should be specified when using a range or comma-separated list to identify
multiple snapshots.
.Bl -tag -width "-R"
.It Fl R
Recursively destroy all clones of these snapshots, including the clones,
snapshots, and children.
If this flag is specified, the
.Fl d
flag will have no effect.
.It Fl d
Defer snapshot deletion.
.It Fl n
Do a dry-run
.Pq Qq No-op
deletion.
No data will be deleted.
This is useful in conjunction with the
.Fl p
or
.Fl v
flags to determine what data would be deleted.
.It Fl p
Print machine-parsable verbose information about the deleted data.
.It Fl r
Destroy
.Pq or mark for deferred deletion
all snapshots with this name in descendent file systems.
.It Fl v
Print verbose information about the deleted data.
.Pp
Extreme care should be taken when applying either the
.Fl r
or the
.Fl R
options, as they can destroy large portions of a pool and cause unexpected
behavior for mounted file systems in use.
.El
.It Xo
.Nm
.Cm destroy
.Ar filesystem Ns | Ns Ar volume Ns # Ns Ar bookmark
.Xc
The given bookmark is destroyed.
.It Xo
.Nm
.Cm snapshot
.Op Fl r
.Oo Fl o Ar property Ns = Ns value Oc Ns ...
.Ar filesystem Ns @ Ns Ar snapname Ns | Ns Ar volume Ns @ Ns Ar snapname Ns ...
.Xc
Creates snapshots with the given names.
All previous modifications by successful system calls to the file system are
part of the snapshots.
Snapshots are taken atomically, so that all snapshots correspond to the same
moment in time.
See the
.Sx Snapshots
section for details.
.Bl -tag -width "-o"
.It Fl o Ar property Ns = Ns Ar value
Sets the specified property; see
.Nm zfs Cm create
for details.
.It Fl r
Recursively create snapshots of all descendent datasets
.El
.It Xo
.Nm
.Cm rollback
.Op Fl Rfr
.Ar snapshot
.Xc
Roll back the given dataset to a previous snapshot.
When a dataset is rolled back, all data that has changed since the snapshot is
discarded, and the dataset reverts to the state at the time of the snapshot.
By default, the command refuses to roll back to a snapshot other than the most
recent one.
In order to do so, all intermediate snapshots and bookmarks must be destroyed by
specifying the
.Fl r
option.
.Pp
The
.Fl rR
options do not recursively destroy the child snapshots of a recursive snapshot.
Only direct snapshots of the specified filesystem are destroyed by either of
these options.
To completely roll back a recursive snapshot, you must rollback the individual
child snapshots.
.Bl -tag -width "-R"
.It Fl R
Destroy any more recent snapshots and bookmarks, as well as any clones of those
snapshots.
.It Fl f
Used with the
.Fl R
option to force an unmount of any clone file systems that are to be destroyed.
.It Fl r
Destroy any snapshots and bookmarks more recent than the one specified.
.El
.It Xo
.Nm
.Cm clone
.Op Fl p
.Oo Fl o Ar property Ns = Ns Ar value Oc Ns ...
.Ar snapshot Ar filesystem Ns | Ns Ar volume
.Xc
Creates a clone of the given snapshot.
See the
.Sx Clones
section for details.
The target dataset can be located anywhere in the ZFS hierarchy, and is created
as the same type as the original.
.Bl -tag -width "-o"
.It Fl o Ar property Ns = Ns Ar value
Sets the specified property; see
.Nm zfs Cm create
for details.
.It Fl p
Creates all the non-existing parent datasets.
Datasets created in this manner are automatically mounted according to the
.Sy mountpoint
property inherited from their parent.
If the target filesystem or volume already exists, the operation completes
successfully.
.El
.It Xo
.Nm
.Cm promote
.Ar clone-filesystem
.Xc
Promotes a clone file system to no longer be dependent on its
.Qq origin
snapshot.
This makes it possible to destroy the file system that the clone was created
from.
The clone parent-child dependency relationship is reversed, so that the origin
file system becomes a clone of the specified file system.
.Pp
The snapshot that was cloned, and any snapshots previous to this snapshot, are
now owned by the promoted clone.
The space they use moves from the origin file system to the promoted clone, so
enough space must be available to accommodate these snapshots.
No new space is consumed by this operation, but the space accounting is
adjusted.
The promoted clone must not have any conflicting snapshot names of its own.
The
.Cm rename
subcommand can be used to rename any conflicting snapshots.
.It Xo
.Nm
.Cm rename
.Op Fl f
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Xc
.It Xo
.Nm
.Cm rename
.Op Fl fp
.Ar filesystem Ns | Ns Ar volume
.Ar filesystem Ns | Ns Ar volume
.Xc
Renames the given dataset.
The new target can be located anywhere in the ZFS hierarchy, with the exception
of snapshots.
Snapshots can only be renamed within the parent file system or volume.
When renaming a snapshot, the parent file system of the snapshot does not need
to be specified as part of the second argument.
Renamed file systems can inherit new mount points, in which case they are
unmounted and remounted at the new mount point.
.Bl -tag -width "-a"
.It Fl f
Force unmount any filesystems that need to be unmounted in the process.
.It Fl p
Creates all the nonexistent parent datasets.
Datasets created in this manner are automatically mounted according to the
.Sy mountpoint
property inherited from their parent.
.El
.It Xo
.Nm
.Cm rename
.Fl r
.Ar snapshot Ar snapshot
.Xc
Recursively rename the snapshots of all descendent datasets.
Snapshots are the only dataset that can be renamed recursively.
.It Xo
.Nm
.Cm list
.Op Fl r Ns | Ns Fl d Ar depth
.Op Fl Hp
.Oo Fl o Ar property Ns Oo , Ns Ar property Oc Ns ... Oc
.Oo Fl s Ar property Oc Ns ...
.Oo Fl S Ar property Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Oo Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Oc Ns ...
.Xc
Lists the property information for the given datasets in tabular form.
If specified, you can list property information by the absolute pathname or the
relative pathname.
By default, all file systems and volumes are displayed.
Snapshots are displayed if the
.Sy listsnaps
property is
.Sy on
.Po the default is
.Sy off
.Pc .
The following fields are displayed,
.Sy name Ns \&, Ns Sy used Ns \&, Ns Sy available Ns \&, Ns Sy referenced Ns \&, Ns
.Sy mountpoint .
.Bl -tag -width "-H"
.It Fl H
Used for scripting mode.
Do not print headers and separate fields by a single tab instead of arbitrary
white space.
.It Fl S Ar property
Same as the
.Fl s
option, but sorts by property in descending order.
.It Fl d Ar depth
Recursively display any children of the dataset, limiting the recursion to
.Ar depth .
A
.Ar depth
of
.Sy 1
will display only the dataset and its direct children.
.It Fl o Ar property
A comma-separated list of properties to display.
The property must be:
.Bl -bullet
.It
One of the properties described in the
.Sx Native Properties
section
.It
A user property
.It
The value
.Sy name
to display the dataset name
.It
The value
.Sy space
to display space usage properties on file systems and volumes.
This is a shortcut for specifying
.Fl o Sy name Ns \&, Ns Sy avail Ns \&, Ns Sy used Ns \&, Ns Sy usedsnap Ns \&, Ns
.Sy usedds Ns \&, Ns Sy usedrefreserv Ns \&, Ns Sy usedchild Fl t
.Sy filesystem Ns \&, Ns Sy volume
syntax.
.El
.It Fl p
Display numbers in parsable
.Pq exact
values.
.It Fl r
Recursively display any children of the dataset on the command line.
.It Fl s Ar property
A property for sorting the output by column in ascending order based on the
value of the property.
The property must be one of the properties described in the
.Sx Properties
section, or the special value
.Sy name
to sort by the dataset name.
Multiple properties can be specified at one time using multiple
.Fl s
property options.
Multiple
.Fl s
options are evaluated from left to right in decreasing order of importance.
The following is a list of sorting criteria:
.Bl -bullet
.It
Numeric types sort in numeric order.
.It
String types sort in alphabetical order.
.It
Types inappropriate for a row sort that row to the literal bottom, regardless of
the specified ordering.
.El
.Pp
If no sorting options are specified the existing behavior of
.Nm zfs Cm list
is preserved.
.It Fl t Ar type
A comma-separated list of types to display, where
.Ar type
is one of
.Sy filesystem ,
.Sy snapshot ,
.Sy volume ,
.Sy bookmark ,
or
.Sy all .
For example, specifying
.Fl t Sy snapshot
displays only snapshots.
.El
.It Xo
.Nm
.Cm set
.Ar property Ns = Ns Ar value Oo Ar property Ns = Ns Ar value Oc Ns ...
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns ...
.Xc
Sets the property or list of properties to the given value(s) for each dataset.
Only some properties can be edited.
See the
.Sx Properties
section for more information on what properties can be set and acceptable
values.
Numeric values can be specified as exact values, or in a human-readable form
with a suffix of
.Sy B , K , M , G , T , P , E , Z
.Po for bytes, kilobytes, megabytes, gigabytes, terabytes, petabytes, exabytes,
or zettabytes, respectively
.Pc .
User properties can be set on snapshots.
For more information, see the
.Sx User Properties
section.
.It Xo
.Nm
.Cm get
.Op Fl r Ns | Ns Fl d Ar depth
.Op Fl Hp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar source Ns Oo , Ns Ar source Oc Ns ... Oc
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Cm all | Ar property Ns Oo , Ns Ar property Oc Ns ...
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns | Ns Ar bookmark Ns ...
.Xc
Displays properties for the given datasets.
If no datasets are specified, then the command displays properties for all
datasets on the system.
For each property, the following columns are displayed:
.Bd -literal
    name      Dataset name
    property  Property name
    value     Property value
    source    Property source.  Can either be local, default,
              temporary, inherited, or none (-).
.Ed
.Pp
All columns are displayed by default, though this can be controlled by using the
.Fl o
option.
This command takes a comma-separated list of properties as described in the
.Sx Native Properties
and
.Sx User Properties
sections.
.Pp
The special value
.Sy all
can be used to display all properties that apply to the given dataset's type
.Pq filesystem, volume, snapshot, or bookmark .
.Bl -tag -width "-H"
.It Fl H
Display output in a form more easily parsed by scripts.
Any headers are omitted, and fields are explicitly separated by a single tab
instead of an arbitrary amount of space.
.It Fl d Ar depth
Recursively display any children of the dataset, limiting the recursion to
.Ar depth .
A depth of
.Sy 1
will display only the dataset and its direct children.
.It Fl o Ar field
A comma-separated list of columns to display.
.Sy name Ns \&, Ns Sy property Ns \&, Ns Sy value Ns \&, Ns Sy source
is the default value.
.It Fl p
Display numbers in parsable
.Pq exact
values.
.It Fl r
Recursively display properties for any children.
.It Fl s Ar source
A comma-separated list of sources to display.
Those properties coming from a source other than those in this list are ignored.
Each source must be one of the following:
.Sy local ,
.Sy default ,
.Sy inherited ,
.Sy temporary ,
and
.Sy none .
The default value is all sources.
.It Fl t Ar type
A comma-separated list of types to display, where
.Ar type
is one of
.Sy filesystem ,
.Sy snapshot ,
.Sy volume ,
.Sy bookmark ,
or
.Sy all .
.El
.It Xo
.Nm
.Cm inherit
.Op Fl rS
.Ar property Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot Ns ...
.Xc
Clears the specified property, causing it to be inherited from an ancestor,
restored to default if no ancestor has the property set, or with the
.Fl S
option reverted to the received value if one exists.
See the
.Sx Properties
section for a listing of default values, and details on which properties can be
inherited.
.Bl -tag -width "-r"
.It Fl r
Recursively inherit the given property for all children.
.It Fl S
Revert the property to the received value if one exists; otherwise operate as
if the
.Fl S
option was not specified.
.El
.It Xo
.Nm
.Cm upgrade
.Xc
Displays a list of file systems that are not the most recent version.
.It Xo
.Nm
.Cm upgrade
.Fl v
.Xc
Displays a list of currently supported file system versions.
.It Xo
.Nm
.Cm upgrade
.Op Fl r
.Op Fl V Ar version
.Fl a | Ar filesystem
.Xc
Upgrades file systems to a new on-disk version.
Once this is done, the file systems will no longer be accessible on systems
running older versions of the software.
.Nm zfs Cm send
streams generated from new snapshots of these file systems cannot be accessed on
systems running older versions of the software.
.Pp
In general, the file system version is independent of the pool version.
See
.Xr zpool 8
for information on the
.Nm zpool Cm upgrade
command.
.Pp
In some cases, the file system version and the pool version are interrelated and
the pool version must be upgraded before the file system version can be
upgraded.
.Bl -tag -width "-V"
.It Fl V Ar version
Upgrade to the specified
.Ar version .
If the
.Fl V
flag is not specified, this command upgrades to the most recent version.
This
option can only be used to increase the version number, and only up to the most
recent version supported by this software.
.It Fl a
Upgrade all file systems on all imported pools.
.It Ar filesystem
Upgrade the specified file system.
.It Fl r
Upgrade the specified file system and all descendent file systems.
.El
.It Xo
.Nm
.Cm userspace
.Op Fl Hinp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar field Oc Ns ...
.Oo Fl S Ar field Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar snapshot
.Xc
Displays space consumed by, and quotas on, each user in the specified filesystem
or snapshot.
This corresponds to the
.Sy userused@ Ns Em user ,
.Sy userobjused@ Ns Em user ,
.Sy userquota@ Ns Em user,
and
.Sy userobjquota@ Ns Em user
properties.
.Bl -tag -width "-H"
.It Fl H
Do not print headers, use tab-delimited output.
.It Fl S Ar field
Sort by this field in reverse order.
See
.Fl s .
.It Fl i
Translate SID to POSIX ID.
The POSIX ID may be ephemeral if no mapping exists.
Normal POSIX interfaces
.Po for example,
.Xr stat 2 ,
.Nm ls Fl l
.Pc
perform this translation, so the
.Fl i
option allows the output from
.Nm zfs Cm userspace
to be compared directly with those utilities.
However,
.Fl i
may lead to confusion if some files were created by an SMB user before a
SMB-to-POSIX name mapping was established.
In such a case, some files will be owned by the SMB entity and some by the POSIX
entity.
However, the
.Fl i
option will report that the POSIX entity has the total usage and quota for both.
.It Fl n
Print numeric ID instead of user/group name.
.It Fl o Ar field Ns Oo , Ns Ar field Oc Ns ...
Display only the specified fields from the following set:
.Sy type ,
.Sy name ,
.Sy used ,
.Sy quota .
The default is to display all fields.
.It Fl p
Use exact
.Pq parsable
numeric output.
.It Fl s Ar field
Sort output by this field.
The
.Fl s
and
.Fl S
flags may be specified multiple times to sort first by one field, then by
another.
The default is
.Fl s Sy type Fl s Sy name .
.It Fl t Ar type Ns Oo , Ns Ar type Oc Ns ...
Print only the specified types from the following set:
.Sy all ,
.Sy posixuser ,
.Sy smbuser ,
.Sy posixgroup ,
.Sy smbgroup .
The default is
.Fl t Sy posixuser Ns \&, Ns Sy smbuser .
The default can be changed to include group types.
.El
.It Xo
.Nm
.Cm groupspace
.Op Fl Hinp
.Oo Fl o Ar field Ns Oo , Ns Ar field Oc Ns ... Oc
.Oo Fl s Ar field Oc Ns ...
.Oo Fl S Ar field Oc Ns ...
.Oo Fl t Ar type Ns Oo , Ns Ar type Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar snapshot
.Xc
Displays space consumed by, and quotas on, each group in the specified
filesystem or snapshot.
This subcommand is identical to
.Nm zfs Cm userspace ,
except that the default types to display are
.Fl t Sy posixgroup Ns \&, Ns Sy smbgroup .
.It Xo
.Nm
.Cm mount
.Xc
Displays all ZFS file systems currently mounted.
.It Xo
.Nm
.Cm mount
.Op Fl Olv
.Op Fl o Ar options
.Fl a | Ar filesystem
.Xc
Mounts ZFS file systems.
.Bl -tag -width "-O"
.It Fl O
Perform an overlay mount.
See
.Xr mount 8
for more information.
.It Fl a
Mount all available ZFS file systems.
Invoked automatically as part of the boot process.
.It Ar filesystem
Mount the specified filesystem.
.It Fl o Ar options
An optional, comma-separated list of mount options to use temporarily for the
duration of the mount.
See the
.Sx Temporary Mount Point Properties
section for details.
.It Fl l
Load keys for encrypted filesystems as they are being mounted. This is
equivalent to executing
.Nm zfs Cm load-key
on each encryption root before mounting it. Note that if a filesystem has a
.Sy keylocation
of
.Sy prompt
this will cause the terminal to interactively block after asking for the key.
.It Fl v
Report mount progress.
.El
.It Xo
.Nm
.Cm unmount
.Op Fl f
.Fl a | Ar filesystem Ns | Ns Ar mountpoint
.Xc
Unmounts currently mounted ZFS file systems.
.Bl -tag -width "-a"
.It Fl a
Unmount all available ZFS file systems.
Invoked automatically as part of the shutdown process.
.It Ar filesystem Ns | Ns Ar mountpoint
Unmount the specified filesystem.
The command can also be given a path to a ZFS file system mount point on the
system.
.It Fl f
Forcefully unmount the file system, even if it is currently in use.
.El
.It Xo
.Nm
.Cm share
.Fl a | Ar filesystem
.Xc
Shares available ZFS file systems.
.Bl -tag -width "-a"
.It Fl a
Share all available ZFS file systems.
Invoked automatically as part of the boot process.
.It Ar filesystem
Share the specified filesystem according to the
.Sy sharenfs
and
.Sy sharesmb
properties.
File systems are shared when the
.Sy sharenfs
or
.Sy sharesmb
property is set.
.El
.It Xo
.Nm
.Cm unshare
.Fl a | Ar filesystem Ns | Ns Ar mountpoint
.Xc
Unshares currently shared ZFS file systems.
.Bl -tag -width "-a"
.It Fl a
Unshare all available ZFS file systems.
Invoked automatically as part of the shutdown process.
.It Ar filesystem Ns | Ns Ar mountpoint
Unshare the specified filesystem.
The command can also be given a path to a ZFS file system shared on the system.
.El
.It Xo
.Nm
.Cm bookmark
.Ar snapshot bookmark
.Xc
Creates a bookmark of the given snapshot.
Bookmarks mark the point in time when the snapshot was created, and can be used
as the incremental source for a
.Nm zfs Cm send
command.
.Pp
This feature must be enabled to be used.
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy bookmarks
feature.
.It Xo
.Nm
.Cm send
.Op Fl DLPRcenpvw
.Op Oo Fl I Ns | Ns Fl i Oc Ar snapshot
.Ar snapshot
.Xc
Creates a stream representation of the second
.Ar snapshot ,
which is written to standard output.
The output can be redirected to a file or to a different system
.Po for example, using
.Xr ssh 1
.Pc .
By default, a full stream is generated.
.Bl -tag -width "-D"
.It Fl D, -dedup
Generate a deduplicated stream.
Blocks which would have been sent multiple times in the send stream will only be
sent once.
The receiving system must also support this feature to receive a deduplicated
stream.
This flag can be used regardless of the dataset's
.Sy dedup
property, but performance will be much better if the filesystem uses a
dedup-capable checksum
.Po for example,
.Sy sha256
.Pc .
.It Fl I Ar snapshot
Generate a stream package that sends all intermediary snapshots from the first
snapshot to the second snapshot.
For example,
.Fl I Em @a Em fs@d
is similar to
.Fl i Em @a Em fs@b Ns \&; Fl i Em @b Em fs@c Ns \&; Fl i Em @c Em fs@d .
The incremental source may be specified as with the
.Fl i
option.
.It Fl L, -large-block
Generate a stream which may contain blocks larger than 128KB.
This flag has no effect if the
.Sy large_blocks
pool feature is disabled, or if the
.Sy recordsize
property of this filesystem has never been set above 128KB.
The receiving system must have the
.Sy large_blocks
pool feature enabled as well.
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy large_blocks
feature.
.It Fl P, -parsable
Print machine-parsable verbose information about the stream package generated.
.It Fl R, -replicate
Generate a replication stream package, which will replicate the specified
file system, and all descendent file systems, up to the named snapshot.
When received, all properties, snapshots, descendent file systems, and clones
are preserved.
.Pp
If the
.Fl i
or
.Fl I
flags are used in conjunction with the
.Fl R
flag, an incremental replication stream is generated.
The current values of properties, and current snapshot and file system names are
set when the stream is received.
If the
.Fl F
flag is specified when this stream is received, snapshots and file systems that
do not exist on the sending side are destroyed.
.It Fl e, -embed
Generate a more compact stream by using
.Sy WRITE_EMBEDDED
records for blocks which are stored more compactly on disk by the
.Sy embedded_data
pool feature.
This flag has no effect if the
.Sy embedded_data
feature is disabled.
The receiving system must have the
.Sy embedded_data
feature enabled.
If the
.Sy lz4_compress
feature is active on the sending system, then the receiving system must have
that feature enabled as well. Datasets that are sent with this flag may not be
received as an encrypted dataset, since encrypted datasets cannot use the
.Sy embedded_data
feature.
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy embedded_data
feature.
.It Fl c, -compressed
Generate a more compact stream by using compressed WRITE records for blocks
which are compressed on disk and in memory
.Po see the
.Sy compression
property for details
.Pc .
If the
.Sy lz4_compress
feature is active on the sending system, then the receiving system must have
that feature enabled as well.
If the
.Sy large_blocks
feature is enabled on the sending system but the
.Fl L
option is not supplied in conjunction with
.Fl c ,
then the data will be decompressed before sending so it can be split into
smaller block sizes.
.It Fl w, -raw
For encrypted datasets, send data exactly as it exists on disk. This allows
backups to be taken even if encryption keys are not currently loaded. The
backup may then be received on an untrusted machine since that machine will
not have the encryption keys to read the protected data or alter it without
being detected. Upon being received, the dataset will have the same encryption
keys as it did on the send side, although the
.Sy keylocation
property will be defaulted to
.Sy prompt
if not otherwise provided. For unencrypted datasets, this flag will be
equivalent to
.Fl Lec .
Note that if you do not use this flag for sending encrypted datasets, data will
be sent unencrypted and may be re-encrypted with a different encryption key on
the receiving system, which will disable the ability to do a raw send to that
system for incrementals.
.It Fl i Ar snapshot
Generate an incremental stream from the first
.Ar snapshot
.Pq the incremental source
to the second
.Ar snapshot
.Pq the incremental target .
The incremental source can be specified as the last component of the snapshot
name
.Po the
.Sy @
character and following
.Pc
and it is assumed to be from the same file system as the incremental target.
.Pp
If the destination is a clone, the source may be the origin snapshot, which must
be fully specified
.Po for example,
.Em pool/fs@origin ,
not just
.Em @origin
.Pc .
.It Fl n, -dryrun
Do a dry-run
.Pq Qq No-op
send.
Do not generate any actual send data.
This is useful in conjunction with the
.Fl v
or
.Fl P
flags to determine what data will be sent.
In this case, the verbose output will be written to standard output
.Po contrast with a non-dry-run, where the stream is written to standard output
and the verbose output goes to standard error
.Pc .
.It Fl p, -props
Include the dataset's properties in the stream.
This flag is implicit when
.Fl R
is specified.
The receiving system must also support this feature. Sends of encrypted datasets
must use
.Fl w
when using this flag.
.It Fl v, -verbose
Print verbose information about the stream package generated.
This information includes a per-second report of how much data has been sent.
.Pp
The format of the stream is committed.
You will be able to receive your streams on future versions of ZFS.
.El
.It Xo
.Nm
.Cm send
.Op Fl LPcenvw
.Op Fl i Ar snapshot Ns | Ns Ar bookmark
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Xc
Generate a send stream, which may be of a filesystem, and may be incremental
from a bookmark.
If the destination is a filesystem or volume, the pool must be read-only, or the
filesystem must not be mounted.
When the stream generated from a filesystem or volume is received, the default
snapshot name will be
.Qq --head-- .
.Bl -tag -width "-L"
.It Fl L, -large-block
Generate a stream which may contain blocks larger than 128KB.
This flag has no effect if the
.Sy large_blocks
pool feature is disabled, or if the
.Sy recordsize
property of this filesystem has never been set above 128KB.
The receiving system must have the
.Sy large_blocks
pool feature enabled as well.
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy large_blocks
feature.
.It Fl P, -parsable
Print machine-parsable verbose information about the stream package generated.
.It Fl c, -compressed
Generate a more compact stream by using compressed WRITE records for blocks
which are compressed on disk and in memory
.Po see the
.Sy compression
property for details
.Pc .
If the
.Sy lz4_compress
feature is active on the sending system, then the receiving system must have
that feature enabled as well.
If the
.Sy large_blocks
feature is enabled on the sending system but the
.Fl L
option is not supplied in conjunction with
.Fl c ,
then the data will be decompressed before sending so it can be split into
smaller block sizes.
.It Fl w, -raw
For encrypted datasets, send data exactly as it exists on disk. This allows
backups to be taken even if encryption keys are not currently loaded. The
backup may then be received on an untrusted machine since that machine will
not have the encryption keys to read the protected data or alter it without
being detected. Upon being received, the dataset will have the same encryption
keys as it did on the send side, although the
.Sy keylocation
property will be defaulted to
.Sy prompt
if not otherwise provided. For unencrypted datasets, this flag will be
equivalent to
.Fl Lec .
Note that if you do not use this flag for sending encrypted datasets, data will
be sent unencrypted and may be re-encrypted with a different encryption key on
the receiving system, which will disable the ability to do a raw send to that
system for incrementals.
.It Fl e, -embed
Generate a more compact stream by using
.Sy WRITE_EMBEDDED
records for blocks which are stored more compactly on disk by the
.Sy embedded_data
pool feature.
This flag has no effect if the
.Sy embedded_data
feature is disabled.
The receiving system must have the
.Sy embedded_data
feature enabled.
If the
.Sy lz4_compress
feature is active on the sending system, then the receiving system must have
that feature enabled as well. Datasets that are sent with this flag may not be
received as an encrypted dataset, since encrypted datasets cannot use the
.Sy embedded_data
feature.
See
.Xr zpool-features 5
for details on ZFS feature flags and the
.Sy embedded_data
feature.
.It Fl i Ar snapshot Ns | Ns Ar bookmark
Generate an incremental send stream.
The incremental source must be an earlier snapshot in the destination's history.
It will commonly be an earlier snapshot in the destination's file system, in
which case it can be specified as the last component of the name
.Po the
.Sy #
or
.Sy @
character and following
.Pc .
.Pp
If the incremental target is a clone, the incremental source can be the origin
snapshot, or an earlier snapshot in the origin's filesystem, or the origin's
origin, etc.
.It Fl n, -dryrun
Do a dry-run
.Pq Qq No-op
send.
Do not generate any actual send data.
This is useful in conjunction with the
.Fl v
or
.Fl P
flags to determine what data will be sent.
In this case, the verbose output will be written to standard output
.Po contrast with a non-dry-run, where the stream is written to standard output
and the verbose output goes to standard error
.Pc .
.It Fl v, -verbose
Print verbose information about the stream package generated.
This information includes a per-second report of how much data has been sent.
.El
.It Xo
.Nm
.Cm send
.Op Fl Penv
.Fl t
.Ar receive_resume_token
.Xc
Creates a send stream which resumes an interrupted receive.
The
.Ar receive_resume_token
is the value of this property on the filesystem or volume that was being
received into.
See the documentation for
.Sy zfs receive -s
for more details.
.It Xo
.Nm
.Cm receive
.Op Fl Fnsuv
.Op Fl o Sy origin Ns = Ns Ar snapshot
.Op Fl o Ar property Ns = Ns Ar value
.Op Fl x Ar property
.Ar filesystem Ns | Ns Ar volume Ns | Ns Ar snapshot
.Xc
.It Xo
.Nm
.Cm receive
.Op Fl Fnsuv
.Op Fl d Ns | Ns Fl e
.Op Fl o Sy origin Ns = Ns Ar snapshot
.Op Fl o Ar property Ns = Ns Ar value
.Op Fl x Ar property
.Ar filesystem
.Xc
Creates a snapshot whose contents are as specified in the stream provided on
standard input.
If a full stream is received, then a new file system is created as well.
Streams are created using the
.Nm zfs Cm send
subcommand, which by default creates a full stream.
.Nm zfs Cm recv
can be used as an alias for
.Nm zfs Cm receive.
.Pp
If an incremental stream is received, then the destination file system must
already exist, and its most recent snapshot must match the incremental stream's
source.
For
.Sy zvols ,
the destination device link is destroyed and recreated, which means the
.Sy zvol
cannot be accessed during the
.Cm receive
operation.
.Pp
When a snapshot replication package stream that is generated by using the
.Nm zfs Cm send Fl R
command is received, any snapshots that do not exist on the sending location are
destroyed by using the
.Nm zfs Cm destroy Fl d
command.
.Pp
If
.Fl o Em property Ns = Ns Ar value
or
.Fl x Em property
is specified, it applies to the effective value of the property throughout
the entire subtree of replicated datasets. Effective property values will be
set (
.Fl o
) or inherited (
.Fl x
) on the topmost in the replicated subtree. In descendant datasets, if the
property is set by the send stream, it will be overridden by forcing the
property to be inherited from the top‐most file system. Received properties
are retained in spite of being overridden and may be restored with
.Nm zfs Cm inherit Fl S .
Specifying
.Fl o Sy origin Ns = Ns Em snapshot
is a special case because, even if
.Sy origin
is a read-only property and cannot be set, it's allowed to receive the send
stream as a clone of the given snapshot.
.Pp
Raw encrypted send streams (created with
.Nm zfs Cm send Fl w
) may only be received as is, and cannot be re-encrypted, decrypted, or
recompressed by the receive process. Unencrypted streams can be received as
encrypted datasets, either through inheritance or by specifying encryption
parameters with the
.Fl o
options.
.Pp
The name of the snapshot
.Pq and file system, if a full stream is received
that this subcommand creates depends on the argument type and the use of the
.Fl d
or
.Fl e
options.
.Pp
If the argument is a snapshot name, the specified
.Ar snapshot
is created.
If the argument is a file system or volume name, a snapshot with the same name
as the sent snapshot is created within the specified
.Ar filesystem
or
.Ar volume .
If neither of the
.Fl d
or
.Fl e
options are specified, the provided target snapshot name is used exactly as
provided.
.Pp
The
.Fl d
and
.Fl e
options cause the file system name of the target snapshot to be determined by
appending a portion of the sent snapshot's name to the specified target
.Ar filesystem .
If the
.Fl d
option is specified, all but the first element of the sent snapshot's file
system path
.Pq usually the pool name
is used and any required intermediate file systems within the specified one are
created.
If the
.Fl e
option is specified, then only the last element of the sent snapshot's file
system name
.Pq i.e. the name of the source file system itself
is used as the target file system name.
.Bl -tag -width "-F"
.It Fl F
Force a rollback of the file system to the most recent snapshot before
performing the receive operation.
If receiving an incremental replication stream
.Po for example, one generated by
.Nm zfs Cm send Fl R Op Fl i Ns | Ns Fl I
.Pc ,
destroy snapshots and file systems that do not exist on the sending side.
.It Fl d
Discard the first element of the sent snapshot's file system name, using the
remaining elements to determine the name of the target file system for the new
snapshot as described in the paragraph above.
.It Fl e
Discard all but the last element of the sent snapshot's file system name, using
that element to determine the name of the target file system for the new
snapshot as described in the paragraph above.
.It Fl n
Do not actually receive the stream.
This can be useful in conjunction with the
.Fl v
option to verify the name the receive operation would use.
.It Fl o Sy origin Ns = Ns Ar snapshot
Forces the stream to be received as a clone of the given snapshot.
If the stream is a full send stream, this will create the filesystem
described by the stream as a clone of the specified snapshot.
Which snapshot was specified will not affect the success or failure of the
receive, as long as the snapshot does exist.
If the stream is an incremental send stream, all the normal verification will be
performed.
.It Fl o Em property Ns = Ns Ar value
Sets the specified property as if the command
.Nm zfs Cm set Em property Ns = Ns Ar value
was invoked immediately before the receive. When receiving a stream from
.Nm zfs Cm send Fl R ,
causes the property to be inherited by all descendant datasets, as through
.Nm zfs Cm inherit Em property
was run on any descendant datasets that have this property set on the
sending system.
.Pp
Any editable property can be set at receive time. Set-once properties bound
to the received data, such as
.Sy normalization
and
.Sy casesensitivity ,
cannot be set at receive time even when the datasets are newly created by
.Nm zfs Cm receive .
Additionally both settable properties
.Sy version
and
.Sy volsize
cannot be set at receive time.
.Pp
The
.Fl o
option may be specified multiple times, for different properties. An error
results if the same property is specified in multiple
.Fl o
or
.Fl x
options.
.It Fl s
If the receive is interrupted, save the partially received state, rather
than deleting it.
Interruption may be due to premature termination of the stream
.Po e.g. due to network failure or failure of the remote system
if the stream is being read over a network connection
.Pc ,
a checksum error in the stream, termination of the
.Nm zfs Cm receive
process, or unclean shutdown of the system.
.Pp
The receive can be resumed with a stream generated by
.Nm zfs Cm send Fl t Ar token ,
where the
.Ar token
is the value of the
.Sy receive_resume_token
property of the filesystem or volume which is received into.
.Pp
To use this flag, the storage pool must have the
.Sy extensible_dataset
feature enabled.
See
.Xr zpool-features 5
for details on ZFS feature flags.
.It Fl u
File system that is associated with the received stream is not mounted.
.It Fl v
Print verbose information about the stream and the time required to perform the
receive operation.
.It Fl x Em property
Ensures that the effective value of the specified property after the
receive is unaffected by the value of that property in the send stream (if any),
as if the property had been excluded from the send stream.
.Pp
If the specified property is not present in the send stream, this option does
nothing.
.Pp
If a received property needs to be overridden, the effective value will be
set or inherited, depending on whether the property is inheritable or not.
.Pp
In the case of an incremental update,
.Fl x
leaves any existing local setting or explicit inheritance unchanged.
.Pp
All
.Fl o
restrictions on set-once and special properties apply equally to
.Fl x .
.El
.It Xo
.Nm
.Cm receive
.Fl A
.Ar filesystem Ns | Ns Ar volume
.Xc
Abort an interrupted
.Nm zfs Cm receive Fl s ,
deleting its saved partially received state.
.It Xo
.Nm
.Cm allow
.Ar filesystem Ns | Ns Ar volume
.Xc
Displays permissions that have been delegated on the specified filesystem or
volume.
See the other forms of
.Nm zfs Cm allow
for more information.
.Pp
Delegations are supported under Linux with the exception of
.Sy mount ,
.Sy unmount ,
.Sy mountpoint ,
.Sy canmount ,
.Sy rename ,
and
.Sy share .
These permissions cannot be delegated because the Linux
.Xr mount 8
command restricts modifications of the global namespace to the root user.
.It Xo
.Nm
.Cm allow
.Op Fl dglu
.Ar user Ns | Ns Ar group Ns Oo , Ns Ar user Ns | Ns Ar group Oc Ns ...
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.br
.Nm
.Cm allow
.Op Fl dl
.Fl e Ns | Ns Sy everyone
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Xc
Delegates ZFS administration permission for the file systems to non-privileged
users.
.Bl -tag -width "-d"
.It Fl d
Allow only for the descendent file systems.
.It Fl e Ns | Ns Sy everyone
Specifies that the permissions be delegated to everyone.
.It Fl g Ar group Ns Oo , Ns Ar group Oc Ns ...
Explicitly specify that permissions are delegated to the group.
.It Fl l
Allow
.Qq locally
only for the specified file system.
.It Fl u Ar user Ns Oo , Ns Ar user Oc Ns ...
Explicitly specify that permissions are delegated to the user.
.It Ar user Ns | Ns Ar group Ns Oo , Ns Ar user Ns | Ns Ar group Oc Ns ...
Specifies to whom the permissions are delegated.
Multiple entities can be specified as a comma-separated list.
If neither of the
.Fl gu
options are specified, then the argument is interpreted preferentially as the
keyword
.Sy everyone ,
then as a user name, and lastly as a group name.
To specify a user or group named
.Qq everyone ,
use the
.Fl g
or
.Fl u
options.
To specify a group with the same name as a user, use the
.Fl g
options.
.It Xo
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Xc
The permissions to delegate.
Multiple permissions may be specified as a comma-separated list.
Permission names are the same as ZFS subcommand and property names.
See the property list below.
Property set names, which begin with
.Sy @ ,
may be specified.
See the
.Fl s
form below for details.
.El
.Pp
If neither of the
.Fl dl
options are specified, or both are, then the permissions are allowed for the
file system or volume, and all of its descendents.
.Pp
Permissions are generally the ability to use a ZFS subcommand or change a ZFS
property.
The following permissions are available:
.Bd -literal
NAME             TYPE           NOTES
allow            subcommand     Must also have the permission that is
                                being allowed
clone            subcommand     Must also have the 'create' ability and
                                'mount' ability in the origin file system
create           subcommand     Must also have the 'mount' ability
destroy          subcommand     Must also have the 'mount' ability
diff             subcommand     Allows lookup of paths within a dataset
                                given an object number, and the ability
                                to create snapshots necessary to
                                'zfs diff'.
load-key         subcommand     Allows loading and unloading of encryption key
                                (see 'zfs load-key' and 'zfs unload-key').
change-key       subcommand     Allows changing an encryption key via
                                'zfs change-key'.
mount            subcommand     Allows mount/umount of ZFS datasets
promote          subcommand     Must also have the 'mount' and 'promote'
                                ability in the origin file system
receive          subcommand     Must also have the 'mount' and 'create'
                                ability
rename           subcommand     Must also have the 'mount' and 'create'
                                ability in the new parent
rollback         subcommand     Must also have the 'mount' ability
send             subcommand
share            subcommand     Allows sharing file systems over NFS
                                or SMB protocols
snapshot         subcommand     Must also have the 'mount' ability

groupquota       other          Allows accessing any groupquota@...
                                property
groupused        other          Allows reading any groupused@... property
userprop         other          Allows changing any user property
userquota        other          Allows accessing any userquota@...
                                property
userused         other          Allows reading any userused@... property

aclinherit       property
acltype          property
atime            property
canmount         property
casesensitivity  property
checksum         property
compression      property
copies           property
devices          property
exec             property
filesystem_limit property
mountpoint       property
nbmand           property
normalization    property
primarycache     property
quota            property
readonly         property
recordsize       property
refquota         property
refreservation   property
reservation      property
secondarycache   property
setuid           property
sharenfs         property
sharesmb         property
snapdir          property
snapshot_limit   property
utf8only         property
version          property
volblocksize     property
volsize          property
vscan            property
xattr            property
zoned            property
.Ed
.It Xo
.Nm
.Cm allow
.Fl c
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Xc
Sets
.Qq create time
permissions.
These permissions are granted
.Pq locally
to the creator of any newly-created descendent file system.
.It Xo
.Nm
.Cm allow
.Fl s No @ Ns Ar setname
.Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ...
.Ar filesystem Ns | Ns Ar volume
.Xc
Defines or adds permissions to a permission set.
The set can be used by other
.Nm zfs Cm allow
commands for the specified file system and its descendents.
Sets are evaluated dynamically, so changes to a set are immediately reflected.
Permission sets follow the same naming restrictions as ZFS file systems, but the
name must begin with
.Sy @ ,
and can be no more than 64 characters long.
.It Xo
.Nm
.Cm unallow
.Op Fl dglru
.Ar user Ns | Ns Ar group Ns Oo , Ns Ar user Ns | Ns Ar group Oc Ns ...
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.br
.Nm
.Cm unallow
.Op Fl dlr
.Fl e Ns | Ns Sy everyone
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.br
.Nm
.Cm unallow
.Op Fl r
.Fl c
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Xc
Removes permissions that were granted with the
.Nm zfs Cm allow
command.
No permissions are explicitly denied, so other permissions granted are still in
effect.
For example, if the permission is granted by an ancestor.
If no permissions are specified, then all permissions for the specified
.Ar user ,
.Ar group ,
or
.Sy everyone
are removed.
Specifying
.Sy everyone
.Po or using the
.Fl e
option
.Pc
only removes the permissions that were granted to everyone, not all permissions
for every user and group.
See the
.Nm zfs Cm allow
command for a description of the
.Fl ldugec
options.
.Bl -tag -width "-r"
.It Fl r
Recursively remove the permissions from this file system and all descendents.
.El
.It Xo
.Nm
.Cm unallow
.Op Fl r
.Fl s No @ Ns Ar setname
.Oo Ar perm Ns | Ns @ Ns Ar setname Ns Oo , Ns Ar perm Ns | Ns @ Ns
.Ar setname Oc Ns ... Oc
.Ar filesystem Ns | Ns Ar volume
.Xc
Removes permissions from a permission set.
If no permissions are specified, then all permissions are removed, thus removing
the set entirely.
.It Xo
.Nm
.Cm hold
.Op Fl r
.Ar tag Ar snapshot Ns ...
.Xc
Adds a single reference, named with the
.Ar tag
argument, to the specified snapshot or snapshots.
Each snapshot has its own tag namespace, and tags must be unique within that
space.
.Pp
If a hold exists on a snapshot, attempts to destroy that snapshot by using the
.Nm zfs Cm destroy
command return
.Er EBUSY .
.Bl -tag -width "-r"
.It Fl r
Specifies that a hold with the given tag is applied recursively to the snapshots
of all descendent file systems.
.El
.It Xo
.Nm
.Cm holds
.Op Fl r
.Ar snapshot Ns ...
.Xc
Lists all existing user references for the given snapshot or snapshots.
.Bl -tag -width "-r"
.It Fl r
Lists the holds that are set on the named descendent snapshots, in addition to
listing the holds on the named snapshot.
.El
.It Xo
.Nm
.Cm release
.Op Fl r
.Ar tag Ar snapshot Ns ...
.Xc
Removes a single reference, named with the
.Ar tag
argument, from the specified snapshot or snapshots.
The tag must already exist for each snapshot.
If a hold exists on a snapshot, attempts to destroy that snapshot by using the
.Nm zfs Cm destroy
command return
.Er EBUSY .
.Bl -tag -width "-r"
.It Fl r
Recursively releases a hold with the given tag on the snapshots of all
descendent file systems.
.El
.It Xo
.Nm
.Cm diff
.Op Fl FHt
.Ar snapshot Ar snapshot Ns | Ns Ar filesystem
.Xc
Display the difference between a snapshot of a given filesystem and another
snapshot of that filesystem from a later time or the current contents of the
filesystem.
The first column is a character indicating the type of change, the other columns
indicate pathname, new pathname
.Pq in case of rename ,
change in link count, and optionally file type and/or change time.
The types of change are:
.Bd -literal
-       The path has been removed
+       The path has been created
M       The path has been modified
R       The path has been renamed
.Ed
.Bl -tag -width "-F"
.It Fl F
Display an indication of the type of file, in a manner similar to the
.Fl
option of
.Xr ls 1 .
.Bd -literal
B       Block device
C       Character device
/       Directory
>       Door
|       Named pipe
@       Symbolic link
P       Event port
=       Socket
F       Regular file
.Ed
.It Fl H
Give more parsable tab-separated output, without header lines and without
arrows.
.It Fl t
Display the path's inode change time as the first column of output.
.El
.It Xo
.Nm
.Cm load-key
.Op Fl nr
.Op Fl L Ar keylocation
.Fl a | Ar filesystem
.Xc
Load the key for
.Ar filesystem ,
allowing it and all children that inherit the
.Sy keylocation
property to be accessed. The key will be expected in the format specified by the
.Sy keyformat
and location specified by the
.Sy keylocation
property. Note that if the
.Sy keylocation
is set to
.Sy prompt
the terminal will interactively wait for the key to be entered. Loading a key
will not automatically mount the dataset. If that functionality is desired,
.Nm zfs Cm mount Sy -l
will ask for the key and mount the dataset. Once the key is loaded the
.Sy keystatus
property will become
.Sy available .
.Bl -tag -width "-r"
.It Fl r
Recursively loads the keys for the specified filesystem and all descendent
encryption roots.
.It Fl a
Loads the keys for all encryption roots in all imported pools.
.It Fl n
Do a dry-run
.Pq Qq No-op
load-key. This will cause zfs to simply check that the
provided key is correct. This command may be run even if the key is already
loaded.
.It Fl L Ar keylocation
Use
.Ar keylocation
instead of the
.Sy keylocation
property. This will not change the value of the property on the dataset. Note
that if used with either
.Fl r
or
.Fl a ,
.Ar keylocation
may only be given as
.Sy prompt .
.El
.It Xo
.Nm
.Cm unload-key
.Op Fl r
.Fl a | Ar filesystem
.Xc
Unloads a key from ZFS, removing the ability to access the dataset and all of
its children that inherit the
.Sy keylocation
property. This requires that the dataset is not currently open or mounted. Once
the key is unloaded the
.Sy keystatus
property will become
.Sy unavailable .
.Bl -tag -width "-r"
.It Fl r
Recursively unloads the keys for the specified filesystem and all descendent
encryption roots.
.It Fl a
Unloads the keys for all encryption roots in all imported pools.
.El
.It Xo
.Nm
.Cm change-key
.Op Fl l
.Op Fl o Ar keylocation Ns = Ns Ar value
.Op Fl o Ar keyformat Ns = Ns Ar value
.Op Fl o Ar pbkdf2iters Ns = Ns Ar value
.Ar filesystem
.Xc
.It Xo
.Nm
.Cm change-key
.Fl i
.Op Fl l
.Ar filesystem
.Xc
Allows a user to change the encryption key used to access a dataset. This
command requires that the existing key for the dataset is already loaded into
ZFS. This command may also be used to change the
.Sy keylocation ,
.Sy keyformat ,
and
.Sy pbkdf2iters
properties as needed. If the dataset was not previously an encryption root it
will become one. Alternatively, the
.Fl i
flag may be provided to cause an encryption root to inherit the parent's key
instead.
.Bl -tag -width "-r"
.It Fl l
Ensures the key is loaded before attempting to change the key. This is
effectively equivalent to
.Qq Nm zfs Cm load-key Ar filesystem ; Nm zfs Cm change-key Ar filesystem
.It Fl o Ar property Ns = Ns Ar value
Allows the user to set encryption key properties (
.Sy keyformat ,
.Sy keylocation ,
and
.Sy pbkdf2iters
) while changing the key. This is the only way to alter
.Sy keyformat
and
.Sy pbkdf2iters
after the dataset has been created.
.It Fl i
Indicates that zfs should make
.Ar filesystem
inherit the key of its parent. Note that this command can only be run on an
encryption root that has an encrypted parent.
.El
.El
.Sh EXIT STATUS
The
.Nm
utility exits 0 on success, 1 if an error occurs, and 2 if invalid command line
options were specified.
.Sh EXAMPLES
.Bl -tag -width ""
.It Sy Example 1 No Creating a ZFS File System Hierarchy
The following commands create a file system named
.Em pool/home
and a file system named
.Em pool/home/bob .
The mount point
.Pa /export/home
is set for the parent file system, and is automatically inherited by the child
file system.
.Bd -literal
# zfs create pool/home
# zfs set mountpoint=/export/home pool/home
# zfs create pool/home/bob
.Ed
.It Sy Example 2 No Creating a ZFS Snapshot
The following command creates a snapshot named
.Sy yesterday .
This snapshot is mounted on demand in the
.Pa .zfs/snapshot
directory at the root of the
.Em pool/home/bob
file system.
.Bd -literal
# zfs snapshot pool/home/bob@yesterday
.Ed
.It Sy Example 3 No Creating and Destroying Multiple Snapshots
The following command creates snapshots named
.Sy yesterday
of
.Em pool/home
and all of its descendent file systems.
Each snapshot is mounted on demand in the
.Pa .zfs/snapshot
directory at the root of its file system.
The second command destroys the newly created snapshots.
.Bd -literal
# zfs snapshot -r pool/home@yesterday
# zfs destroy -r pool/home@yesterday
.Ed
.It Sy Example 4 No Disabling and Enabling File System Compression
The following command disables the
.Sy compression
property for all file systems under
.Em pool/home .
The next command explicitly enables
.Sy compression
for
.Em pool/home/anne .
.Bd -literal
# zfs set compression=off pool/home
# zfs set compression=on pool/home/anne
.Ed
.It Sy Example 5 No Listing ZFS Datasets
The following command lists all active file systems and volumes in the system.
Snapshots are displayed if the
.Sy listsnaps
property is
.Sy on .
The default is
.Sy off .
See
.Xr zpool 8
for more information on pool properties.
.Bd -literal
# zfs list
NAME                      USED  AVAIL  REFER  MOUNTPOINT
pool                      450K   457G    18K  /pool
pool/home                 315K   457G    21K  /export/home
pool/home/anne             18K   457G    18K  /export/home/anne
pool/home/bob             276K   457G   276K  /export/home/bob
.Ed
.It Sy Example 6 No Setting a Quota on a ZFS File System
The following command sets a quota of 50 Gbytes for
.Em pool/home/bob .
.Bd -literal
# zfs set quota=50G pool/home/bob
.Ed
.It Sy Example 7 No Listing ZFS Properties
The following command lists all properties for
.Em pool/home/bob .
.Bd -literal
# zfs get all pool/home/bob
NAME           PROPERTY              VALUE                  SOURCE
pool/home/bob  type                  filesystem             -
pool/home/bob  creation              Tue Jul 21 15:53 2009  -
pool/home/bob  used                  21K                    -
pool/home/bob  available             20.0G                  -
pool/home/bob  referenced            21K                    -
pool/home/bob  compressratio         1.00x                  -
pool/home/bob  mounted               yes                    -
pool/home/bob  quota                 20G                    local
pool/home/bob  reservation           none                   default
pool/home/bob  recordsize            128K                   default
pool/home/bob  mountpoint            /pool/home/bob         default
pool/home/bob  sharenfs              off                    default
pool/home/bob  checksum              on                     default
pool/home/bob  compression           on                     local
pool/home/bob  atime                 on                     default
pool/home/bob  devices               on                     default
pool/home/bob  exec                  on                     default
pool/home/bob  setuid                on                     default
pool/home/bob  readonly              off                    default
pool/home/bob  zoned                 off                    default
pool/home/bob  snapdir               hidden                 default
pool/home/bob  acltype               off                    default
pool/home/bob  aclinherit            restricted             default
pool/home/bob  canmount              on                     default
pool/home/bob  xattr                 on                     default
pool/home/bob  copies                1                      default
pool/home/bob  version               4                      -
pool/home/bob  utf8only              off                    -
pool/home/bob  normalization         none                   -
pool/home/bob  casesensitivity       sensitive              -
pool/home/bob  vscan                 off                    default
pool/home/bob  nbmand                off                    default
pool/home/bob  sharesmb              off                    default
pool/home/bob  refquota              none                   default
pool/home/bob  refreservation        none                   default
pool/home/bob  primarycache          all                    default
pool/home/bob  secondarycache        all                    default
pool/home/bob  usedbysnapshots       0                      -
pool/home/bob  usedbydataset         21K                    -
pool/home/bob  usedbychildren        0                      -
pool/home/bob  usedbyrefreservation  0                      -
.Ed
.Pp
The following command gets a single property value.
.Bd -literal
# zfs get -H -o value compression pool/home/bob
on
.Ed
The following command lists all properties with local settings for
.Em pool/home/bob .
.Bd -literal
# zfs get -r -s local -o name,property,value all pool/home/bob
NAME           PROPERTY              VALUE
pool/home/bob  quota                 20G
pool/home/bob  compression           on
.Ed
.It Sy Example 8 No Rolling Back a ZFS File System
The following command reverts the contents of
.Em pool/home/anne
to the snapshot named
.Sy yesterday ,
deleting all intermediate snapshots.
.Bd -literal
# zfs rollback -r pool/home/anne@yesterday
.Ed
.It Sy Example 9 No Creating a ZFS Clone
The following command creates a writable file system whose initial contents are
the same as
.Em pool/home/bob@yesterday .
.Bd -literal
# zfs clone pool/home/bob@yesterday pool/clone
.Ed
.It Sy Example 10 No Promoting a ZFS Clone
The following commands illustrate how to test out changes to a file system, and
then replace the original file system with the changed one, using clones, clone
promotion, and renaming:
.Bd -literal
# zfs create pool/project/production
  populate /pool/project/production with data
# zfs snapshot pool/project/production@today
# zfs clone pool/project/production@today pool/project/beta
  make changes to /pool/project/beta and test them
# zfs promote pool/project/beta
# zfs rename pool/project/production pool/project/legacy
# zfs rename pool/project/beta pool/project/production
  once the legacy version is no longer needed, it can be destroyed
# zfs destroy pool/project/legacy
.Ed
.It Sy Example 11 No Inheriting ZFS Properties
The following command causes
.Em pool/home/bob
and
.Em pool/home/anne
to inherit the
.Sy checksum
property from their parent.
.Bd -literal
# zfs inherit checksum pool/home/bob pool/home/anne
.Ed
.It Sy Example 12 No Remotely Replicating ZFS Data
The following commands send a full stream and then an incremental stream to a
remote machine, restoring them into
.Em poolB/received/fs@a
and
.Em poolB/received/fs@b ,
respectively.
.Em poolB
must contain the file system
.Em poolB/received ,
and must not initially contain
.Em poolB/received/fs .
.Bd -literal
# zfs send pool/fs@a | \e
  ssh host zfs receive poolB/received/fs@a
# zfs send -i a pool/fs@b | \e
  ssh host zfs receive poolB/received/fs
.Ed
.It Sy Example 13 No Using the zfs receive -d Option
The following command sends a full stream of
.Em poolA/fsA/fsB@snap
to a remote machine, receiving it into
.Em poolB/received/fsA/fsB@snap .
The
.Em fsA/fsB@snap
portion of the received snapshot's name is determined from the name of the sent
snapshot.
.Em poolB
must contain the file system
.Em poolB/received .
If
.Em poolB/received/fsA
does not exist, it is created as an empty file system.
.Bd -literal
# zfs send poolA/fsA/fsB@snap | \e
  ssh host zfs receive -d poolB/received
.Ed
.It Sy Example 14 No Setting User Properties
The following example sets the user-defined
.Sy com.example:department
property for a dataset.
.Bd -literal
# zfs set com.example:department=12345 tank/accounting
.Ed
.It Sy Example 15 No Performing a Rolling Snapshot
The following example shows how to maintain a history of snapshots with a
consistent naming scheme.
To keep a week's worth of snapshots, the user destroys the oldest snapshot,
renames the remaining snapshots, and then creates a new snapshot, as follows:
.Bd -literal
# zfs destroy -r pool/users@7daysago
# zfs rename -r pool/users@6daysago @7daysago
# zfs rename -r pool/users@5daysago @6daysago
# zfs rename -r pool/users@yesterday @5daysago
# zfs rename -r pool/users@yesterday @4daysago
# zfs rename -r pool/users@yesterday @3daysago
# zfs rename -r pool/users@yesterday @2daysago
# zfs rename -r pool/users@today @yesterday
# zfs snapshot -r pool/users@today
.Ed
.It Sy Example 16 No Setting sharenfs Property Options on a ZFS File System
The following commands show how to set
.Sy sharenfs
property options to enable
.Sy rw
access for a set of
.Sy IP
addresses and to enable root access for system
.Sy neo
on the
.Em tank/home
file system.
.Bd -literal
# zfs set sharenfs='rw=@123.123.0.0/16,root=neo' tank/home
.Ed
.Pp
If you are using
.Sy DNS
for host name resolution, specify the fully qualified hostname.
.It Sy Example 17 No Delegating ZFS Administration Permissions on a ZFS Dataset
The following example shows how to set permissions so that user
.Sy cindys
can create, destroy, mount, and take snapshots on
.Em tank/cindys .
The permissions on
.Em tank/cindys
are also displayed.
.Bd -literal
# zfs allow cindys create,destroy,mount,snapshot tank/cindys
# zfs allow tank/cindys
---- Permissions on tank/cindys --------------------------------------
Local+Descendent permissions:
        user cindys create,destroy,mount,snapshot
.Ed
.Pp
Because the
.Em tank/cindys
mount point permission is set to 755 by default, user
.Sy cindys
will be unable to mount file systems under
.Em tank/cindys .
Add an ACE similar to the following syntax to provide mount point access:
.Bd -literal
# chmod A+user:cindys:add_subdirectory:allow /tank/cindys
.Ed
.It Sy Example 18 No Delegating Create Time Permissions on a ZFS Dataset
The following example shows how to grant anyone in the group
.Sy staff
to create file systems in
.Em tank/users .
This syntax also allows staff members to destroy their own file systems, but not
destroy anyone else's file system.
The permissions on
.Em tank/users
are also displayed.
.Bd -literal
# zfs allow staff create,mount tank/users
# zfs allow -c destroy tank/users
# zfs allow tank/users
---- Permissions on tank/users ---------------------------------------
Permission sets:
        destroy
Local+Descendent permissions:
        group staff create,mount
.Ed
.It Sy Example 19 No Defining and Granting a Permission Set on a ZFS Dataset
The following example shows how to define and grant a permission set on the
.Em tank/users
file system.
The permissions on
.Em tank/users
are also displayed.
.Bd -literal
# zfs allow -s @pset create,destroy,snapshot,mount tank/users
# zfs allow staff @pset tank/users
# zfs allow tank/users
---- Permissions on tank/users ---------------------------------------
Permission sets:
        @pset create,destroy,mount,snapshot
Local+Descendent permissions:
        group staff @pset
.Ed
.It Sy Example 20 No Delegating Property Permissions on a ZFS Dataset
The following example shows to grant the ability to set quotas and reservations
on the
.Em users/home
file system.
The permissions on
.Em users/home
are also displayed.
.Bd -literal
# zfs allow cindys quota,reservation users/home
# zfs allow users/home
---- Permissions on users/home ---------------------------------------
Local+Descendent permissions:
        user cindys quota,reservation
cindys% zfs set quota=10G users/home/marks
cindys% zfs get quota users/home/marks
NAME              PROPERTY  VALUE  SOURCE
users/home/marks  quota     10G    local
.Ed
.It Sy Example 21 No Removing ZFS Delegated Permissions on a ZFS Dataset
The following example shows how to remove the snapshot permission from the
.Sy staff
group on the
.Em tank/users
file system.
The permissions on
.Em tank/users
are also displayed.
.Bd -literal
# zfs unallow staff snapshot tank/users
# zfs allow tank/users
---- Permissions on tank/users ---------------------------------------
Permission sets:
        @pset create,destroy,mount,snapshot
Local+Descendent permissions:
        group staff @pset
.Ed
.It Sy Example 22 No Showing the differences between a snapshot and a ZFS Dataset
The following example shows how to see what has changed between a prior
snapshot of a ZFS dataset and its current state.
The
.Fl F
option is used to indicate type information for the files affected.
.Bd -literal
# zfs diff -F tank/test@before tank/test
M       /       /tank/test/
M       F       /tank/test/linked      (+1)
R       F       /tank/test/oldname -> /tank/test/newname
-       F       /tank/test/deleted
+       F       /tank/test/created
M       F       /tank/test/modified
.Ed
.It Sy Example 23 No Creating a bookmark
The following example create a bookmark to a snapshot. This bookmark
can then be used instead of snapshot in send streams.
.Bd -literal
# zfs bookmark rpool@snapshot rpool#bookmark
.Ed
.It Sy Example 24 No Setting sharesmb Property Options on a ZFS File System
The following example show how to share SMB filesystem through ZFS. Note that
that a user and his/her password must be given.
.Bd -literal
# smbmount //127.0.0.1/share_tmp /mnt/tmp \\
  -o user=workgroup/turbo,password=obrut,uid=1000
.Ed
.Pp
Minimal
.Em /etc/samba/smb.conf
configuration required:
.Pp
Samba will need to listen to 'localhost' (127.0.0.1) for the ZFS utilities to
communicate with Samba. This is the default behavior for most Linux
distributions.
.Pp
Samba must be able to authenticate a user. This can be done in a number of
ways, depending on if using the system password file, LDAP or the Samba
specific smbpasswd file. How to do this is outside the scope of this manual.
Please refer to the
.Xr smb.conf 5
man page for more information.
.Pp
See the
.Sy USERSHARE section
of the
.Xr smb.conf 5
man page for all configuration options in case you need to modify any options
to the share afterwards. Do note that any changes done with the
.Xr net 8
command will be undone if the share is ever unshared (such as at a reboot etc).
.El
.Sh INTERFACE STABILITY
.Sy Committed .
.Sh SEE ALSO
.Xr attr 1 ,
.Xr gzip 1 ,
.Xr ssh 1 ,
.Xr chmod 2 ,
.Xr fsync 2 ,
.Xr stat 2 ,
.Xr write 2 ,
.Xr acl 5 ,
.Xr attributes 5 ,
.Xr exports 5 ,
.Xr exportfs 8 ,
.Xr mount 8 ,
.Xr net 8 ,
.Xr selinux 8 ,
.Xr zpool 8