1425 lines
42 KiB
Groff
1425 lines
42 KiB
Groff
.\" Copyright (c) 2000, 2003 Robert N. M. Watson
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.\" Copyright (c) 2008-2012 James Gritton
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd July 18, 2022
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.Dt JAIL 8
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.Os
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.Sh NAME
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.Nm jail
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.Nd "manage system jails"
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.Sh SYNOPSIS
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.Nm
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.Op Fl dhilqv
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.Op Fl J Ar jid_file
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.Op Fl u Ar username
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.Op Fl U Ar username
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.Op Fl cmr
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.Ar param Ns = Ns Ar value ...
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.Op Cm command Ns = Ns Ar command ...
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.Nm
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.Op Fl dqv
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.Op Fl f Ar conf_file
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.Op Fl p Ar limit
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.Op Fl cmr
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.Op Ar jail
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.Nm
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.Op Fl qv
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.Op Fl f Ar conf_file
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.Op Fl rR
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.Op Cm * | Ar jail ...
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.Nm
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.Op Fl dhilqv
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.Op Fl J Ar jid_file
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.Op Fl u Ar username
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.Op Fl U Ar username
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.Op Fl n Ar jailname
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.Op Fl s Ar securelevel
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.Ar path hostname ip Ns Op Cm \&, Ns Ar ...
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.Ar command ...
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.Nm
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.Op Fl f Ar conf_file
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.Fl e
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.Ar separator
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.Sh DESCRIPTION
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The
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.Nm
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utility creates new jails, or modifies or removes existing jails.
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It can also print a list of configured jails and their parameters.
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A jail
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.Pq or Dq prison
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is specified via parameters on the command line, or in the
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.Xr jail.conf 5
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file.
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.Pp
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At least one of the options
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.Fl c ,
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.Fl e ,
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.Fl m
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or
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.Fl r
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must be specified.
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These options are used alone or in combination to describe the operation to
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perform:
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.Bl -tag -width indent
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.It Fl c
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Create a new jail.
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The jail
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.Va jid
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and
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.Va name
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parameters (if specified on the command line)
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must not refer to an existing jail.
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.It Fl e Ar separator
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Exhibit a list of all configured non-wildcard jails and their parameters.
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No jail creation, modification or removal performed if this option is used.
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The
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.Ar separator
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string is used to separate parameters.
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Use
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.Xr jls 8
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utility to list running jails.
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.It Fl m
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Modify an existing jail.
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One of the
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.Va jid
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or
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.Va name
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parameters must exist and refer to an existing jail.
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Some parameters may not be changed on a running jail.
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.It Fl r
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Remove the
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.Ar jail
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specified by jid or name.
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All jailed processes are killed, and all jails that are
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children of this jail are also
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removed.
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.It Fl rc
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Restart an existing jail.
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The jail is first removed and then re-created, as if
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.Dq Nm Fl r
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and
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.Dq Nm Fl c
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were run in succession.
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.It Fl cm
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Create a jail if it does not exist, or modify the jail if it does exist.
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.It Fl mr
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Modify an existing jail.
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The jail may be restarted if necessary to modify parameters than could
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not otherwise be changed.
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.It Fl cmr
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Create a jail if it doesn't exist, or modify (and possibly restart) the
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jail if it does exist.
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.El
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.Pp
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Other available options are:
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.Bl -tag -width indent
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.It Fl d
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Allow making changes to a dying jail, equivalent to the
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.Va allow.dying
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parameter.
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.It Fl f Ar conf_file
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Use configuration file
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.Ar conf_file
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instead of the default
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.Pa /etc/jail.conf .
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.It Fl h
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Resolve the
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.Va host.hostname
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parameter (or
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.Va hostname )
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and add all IP addresses returned by the resolver
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to the list of addresses for this jail.
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This is equivalent to the
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.Va ip_hostname
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parameter.
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.It Fl i
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Output (only) the jail identifier of the newly created jail(s).
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This implies the
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.Fl q
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option.
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.It Fl J Ar jid_file
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Write a
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.Ar jid_file
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file, containing the parameters used to start the jail.
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.It Fl l
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Run commands in a clean environment.
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This is deprecated and is equivalent to the exec.clean parameter.
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.It Fl n Ar jailname
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Set the jail's name.
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This is deprecated and is equivalent to the
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.Va name
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parameter.
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.It Fl p Ar limit
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Limit the number of commands from
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.Va exec.*
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that can run simultaneously.
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.It Fl q
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Suppress the message printed whenever a jail is created, modified or removed.
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Only error messages will be printed.
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.It Fl R
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A variation of the
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.Fl r
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option that removes an existing jail without using the configuration file.
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No removal-related parameters for this jail will be used \(em the jail will
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simply be removed.
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.It Fl s Ar securelevel
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Set the
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.Va kern.securelevel
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MIB entry to the specified value inside the newly created jail.
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This is deprecated and is equivalent to the
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.Va securelevel
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parameter.
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.It Fl u Ar username
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The user name from host environment as whom jailed commands should run.
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This is deprecated and is equivalent to the
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.Va exec.jail_user
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and
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.Va exec.system_jail_user
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parameters.
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.It Fl U Ar username
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The user name from the jailed environment as whom jailed commands should run.
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This is deprecated and is equivalent to the
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.Va exec.jail_user
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parameter.
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.It Fl v
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Print a message on every operation, such as running commands and
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mounting filesystems.
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.El
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.Pp
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If no arguments are given after the options, the operation (except
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remove) will be performed on all jails specified in the
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.Xr jail.conf 5
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file.
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A single argument of a jail name will operate only on the specified jail.
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The
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.Fl r
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and
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.Fl R
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options can also remove running jails that aren't in the
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.Xr jail.conf 5
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file, specified by name or jid.
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.Pp
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An argument of
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.Dq *
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is a wildcard that will operate on all jails, regardless of whether
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they appear in
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.Xr jail.conf 5 ;
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this is the surest way for
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.Fl r
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to remove all jails.
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If hierarchical jails exist, a partial-matching wildcard definition may
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be specified.
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For example, an argument of
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.Dq foo.*
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would apply to jails with names like
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.Dq foo.bar
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and
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.Dq foo.bar.baz .
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.Pp
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A jail may be specified with parameters directly on the command line.
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In this case, the
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.Xr jail.conf 5
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file will not be used.
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For backward compatibility, the command line may also have four fixed
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parameters, without names:
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.Ar path ,
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.Ar hostname ,
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.Ar ip ,
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and
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.Ar command .
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This mode will always create a new jail, and the
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.Fl c
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and
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.Fl m
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options do not apply (and must not be present).
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.Ss Jail Parameters
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Parameters in the
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.Xr jail.conf 5
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file, or on the command line, are generally of the form
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.Dq name=value .
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|
Some parameters are boolean, and do not have a value but are set by the
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name alone with or without a
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.Dq no
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prefix, e.g.
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.Va persist
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or
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.Va nopersist .
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|
They can also be given the values
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.Dq true
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|
and
|
|
.Dq false .
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|
Other parameters may have more than one value, specified as a
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|
comma-separated list or with
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.Dq +=
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in the configuration file (see
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.Xr jail.conf 5
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for details).
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.Pp
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The
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.Nm
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utility recognizes two classes of parameters.
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There are the true jail
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parameters that are passed to the kernel when the jail is created,
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which can be seen with
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.Xr jls 8 ,
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and can (usually) be changed with
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.Dq Nm Fl m .
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Then there are pseudo-parameters that are only used by
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.Nm
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itself.
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.Pp
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Jails have a set of core parameters, and kernel modules can add their own
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jail parameters.
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The current set of available parameters can be retrieved via
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.Dq Nm sysctl Fl d Va security.jail.param .
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|
Any parameters not set will be given default values, often based on the
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current environment.
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The core parameters are:
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.Bl -tag -width indent
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.It Va jid
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The jail identifier.
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This will be assigned automatically to a new jail (or can be explicitly
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set), and can be used to identify the jail for later modification, or
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for such commands as
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.Xr jls 8
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or
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.Xr jexec 8 .
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.It Va name
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The jail name.
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This is an arbitrary string that identifies a jail (except it may not
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contain a
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.Sq \&. ) .
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Like the
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.Va jid ,
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it can be passed to later
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.Nm
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commands, or to
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.Xr jls 8
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or
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.Xr jexec 8 .
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If no
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.Va name
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is supplied, a default is assumed that is the same as the
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.Va jid .
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The
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.Va name
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parameter is implied by the
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.Xr jail.conf 5
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file format, and need not be explicitly set when using the configuration
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file.
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.It Va path
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The directory which is to be the root of the jail.
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Any commands run inside the jail, either by
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.Nm
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or from
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.Xr jexec 8 ,
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are run from this directory.
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.It Va ip4.addr
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A list of IPv4 addresses assigned to the jail.
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If this is set, the jail is restricted to using only these addresses.
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Any attempts to use other addresses fail, and attempts to use wildcard
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addresses silently use the jailed address instead.
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For IPv4 the first address given will be used as the source address
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when source address selection on unbound sockets cannot find a better
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match.
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It is only possible to start multiple jails with the same IP address
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if none of the jails has more than this single overlapping IP address
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assigned to itself.
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.It Va ip4.saddrsel
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A boolean option to change the formerly mentioned behaviour and disable
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IPv4 source address selection for the jail in favour of the primary
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IPv4 address of the jail.
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Source address selection is enabled by default for all jails and the
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.Va ip4.nosaddrsel
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setting of a parent jail is not inherited for any child jails.
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.It Va ip4
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Control the availability of IPv4 addresses.
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Possible values are
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.Dq inherit
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to allow unrestricted access to all system addresses,
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.Dq new
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to restrict addresses via
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.Va ip4.addr ,
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and
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.Dq disable
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to stop the jail from using IPv4 entirely.
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Setting the
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.Va ip4.addr
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parameter implies a value of
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.Dq new .
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.It Va ip6.addr , Va ip6.saddrsel , Va ip6
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A set of IPv6 options for the jail, the counterparts to
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.Va ip4.addr ,
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.Va ip4.saddrsel
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and
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.Va ip4
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above.
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.It Va vnet
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Create the jail with its own virtual network stack,
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with its own network interfaces, addresses, routing table, etc.
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The kernel must have been compiled with the
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.Sy VIMAGE option
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for this to be available.
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Possible values are
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.Dq inherit
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to use the system network stack, possibly with restricted IP addresses,
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and
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.Dq new
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to create a new network stack.
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.It Va host.hostname
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The hostname of the jail.
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Other similar parameters are
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.Va host.domainname ,
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.Va host.hostuuid
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and
|
|
.Va host.hostid .
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.It Va host
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Set the origin of hostname and related information.
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Possible values are
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.Dq inherit
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to use the system information and
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.Dq new
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for the jail to use the information from the above fields.
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Setting any of the above fields implies a value of
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.Dq new .
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.It Va securelevel
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The value of the jail's
|
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.Va kern.securelevel
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sysctl.
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A jail never has a lower securelevel than its parent system, but by
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setting this parameter it may have a higher one.
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If the system securelevel is changed, any jail securelevels will be at
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least as secure.
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.It Va devfs_ruleset
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The number of the devfs ruleset that is enforced for mounting devfs in
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this jail.
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A value of zero (default) means no ruleset is enforced.
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Descendant jails inherit the parent jail's devfs ruleset enforcement.
|
|
Mounting devfs inside a jail is possible only if the
|
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.Va allow.mount
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and
|
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.Va allow.mount.devfs
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permissions are effective and
|
|
.Va enforce_statfs
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is set to a value lower than 2.
|
|
Devfs rules and rulesets cannot be viewed or modified from inside a jail.
|
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.Pp
|
|
NOTE: It is important that only appropriate device nodes in devfs be
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exposed to a jail; access to disk devices in the jail may permit processes
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in the jail to bypass the jail sandboxing by modifying files outside of
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the jail.
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See
|
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.Xr devfs 8
|
|
for information on how to use devfs rules to limit access to entries
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|
in the per-jail devfs.
|
|
A simple devfs ruleset for jails is available as ruleset #4 in
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.Pa /etc/defaults/devfs.rules .
|
|
.It Va children.max
|
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The number of child jails allowed to be created by this jail (or by
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|
other jails under this jail).
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|
This limit is zero by default, indicating the jail is not allowed to
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|
create child jails.
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|
See the
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.Sx "Hierarchical Jails"
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|
section for more information.
|
|
.It Va children.cur
|
|
The number of descendants of this jail, including its own child jails
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|
and any jails created under them.
|
|
.It Va enforce_statfs
|
|
This determines what information processes in a jail are able to get
|
|
about mount points.
|
|
It affects the behaviour of the following syscalls:
|
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.Xr statfs 2 ,
|
|
.Xr fstatfs 2 ,
|
|
.Xr getfsstat 2 ,
|
|
and
|
|
.Xr fhstatfs 2
|
|
(as well as similar compatibility syscalls).
|
|
When set to 0, all mount points are available without any restrictions.
|
|
When set to 1, only mount points below the jail's chroot directory are
|
|
visible.
|
|
In addition to that, the path to the jail's chroot directory is removed
|
|
from the front of their pathnames.
|
|
When set to 2 (default), above syscalls can operate only on a mount-point
|
|
where the jail's chroot directory is located.
|
|
.It Va persist
|
|
Setting this boolean parameter allows a jail to exist without any
|
|
processes.
|
|
Normally, a command is run as part of jail creation, and then the jail
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|
is destroyed as its last process exits.
|
|
A new jail must have either the
|
|
.Va persist
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|
parameter or
|
|
.Va exec.start
|
|
or
|
|
.Va command
|
|
pseudo-parameter set.
|
|
.It Va cpuset.id
|
|
The ID of the cpuset associated with this jail (read-only).
|
|
.It Va dying
|
|
This is true if the jail is in the process of shutting down (read-only).
|
|
.It Va parent
|
|
The
|
|
.Va jid
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|
of the parent of this jail, or zero if this is a top-level jail
|
|
(read-only).
|
|
.It Va osrelease
|
|
The string for the jail's
|
|
.Va kern.osrelease
|
|
sysctl and uname -r.
|
|
.It Va osreldate
|
|
The number for the jail's
|
|
.Va kern.osreldate
|
|
and uname -K.
|
|
.It Va allow.*
|
|
Some restrictions of the jail environment may be set on a per-jail
|
|
basis.
|
|
With the exception of
|
|
.Va allow.set_hostname
|
|
and
|
|
.Va allow.reserved_ports ,
|
|
these boolean parameters are off by default.
|
|
.Bl -tag -width indent
|
|
.It Va allow.set_hostname
|
|
The jail's hostname may be changed via
|
|
.Xr hostname 1
|
|
or
|
|
.Xr sethostname 3 .
|
|
.It Va allow.sysvipc
|
|
A process within the jail has access to System V IPC primitives.
|
|
This is deprecated in favor of the per-module parameters (see below).
|
|
When this parameter is set, it is equivalent to setting
|
|
.Va sysvmsg ,
|
|
.Va sysvsem ,
|
|
and
|
|
.Va sysvshm
|
|
all to
|
|
.Dq inherit .
|
|
.It Va allow.raw_sockets
|
|
The jail root is allowed to create raw sockets.
|
|
Setting this parameter allows utilities like
|
|
.Xr ping 8
|
|
and
|
|
.Xr traceroute 8
|
|
to operate inside the jail.
|
|
If this is set, the source IP addresses are enforced to comply
|
|
with the IP address bound to the jail, regardless of whether or not
|
|
the
|
|
.Dv IP_HDRINCL
|
|
flag has been set on the socket.
|
|
Since raw sockets can be used to configure and interact with various
|
|
network subsystems, extra caution should be used where privileged access
|
|
to jails is given out to untrusted parties.
|
|
.It Va allow.chflags
|
|
Normally, privileged users inside a jail are treated as unprivileged by
|
|
.Xr chflags 2 .
|
|
When this parameter is set, such users are treated as privileged, and
|
|
may manipulate system file flags subject to the usual constraints on
|
|
.Va kern.securelevel .
|
|
.It Va allow.mount
|
|
privileged users inside the jail will be able to mount and unmount file
|
|
system types marked as jail-friendly.
|
|
The
|
|
.Xr lsvfs 1
|
|
command can be used to find file system types available for mount from
|
|
within a jail.
|
|
This permission is effective only if
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.devfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
devfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
The devfs ruleset should be restricted from the default by using the
|
|
.Va devfs_ruleset
|
|
option.
|
|
.It Va allow.quotas
|
|
The jail root may administer quotas on the jail's filesystem(s).
|
|
This includes filesystems that the jail may share with other jails or
|
|
with non-jailed parts of the system.
|
|
.It Va allow.read_msgbuf
|
|
Jailed users may read the kernel message buffer.
|
|
If the
|
|
.Va security.bsd.unprivileged_read_msgbuf
|
|
MIB entry is zero, this will be restricted to the root user.
|
|
.It Va allow.socket_af
|
|
Sockets within a jail are normally restricted to IPv4, IPv6, local
|
|
(UNIX), and route. This allows access to other protocol stacks that
|
|
have not had jail functionality added to them.
|
|
.It Va allow.mlock
|
|
Locking or unlocking physical pages in memory are normally not available
|
|
within a jail.
|
|
When this parameter is set, users may
|
|
.Xr mlock 2
|
|
or
|
|
.Xr munlock 2
|
|
memory subject to
|
|
.Va security.bsd.unprivileged_mlock
|
|
and resource limits.
|
|
.It Va allow.reserved_ports
|
|
The jail root may bind to ports lower than 1024.
|
|
.It Va allow.unprivileged_proc_debug
|
|
Unprivileged processes in the jail may use debugging facilities.
|
|
.It Va allow.suser
|
|
The value of the jail's
|
|
.Va security.bsd.suser_enabled
|
|
sysctl.
|
|
The super-user will be disabled automatically if its parent system has it
|
|
disabled.
|
|
The super-user is enabled by default.
|
|
.El
|
|
.El
|
|
.Pp
|
|
Kernel modules may add their own parameters, which only exist when the
|
|
module is loaded.
|
|
These are typically headed under a parameter named after the module,
|
|
with values of
|
|
.Dq inherit
|
|
to give the jail full use of the module,
|
|
.Dq new
|
|
to encapsulate the jail in some module-specific way,
|
|
and
|
|
.Dq disable
|
|
to make the module unavailable to the jail.
|
|
There also may be other parameters to define jail behavior within the module.
|
|
Module-specific parameters include:
|
|
.Bl -tag -width indent
|
|
.It Va allow.mount.fdescfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
fdescfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.fusefs
|
|
privileged users inside the jail will be able to mount and unmount
|
|
fuse-based file systems.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.nullfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
nullfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.procfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
procfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.linprocfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
linprocfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.linsysfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
linsysfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.tmpfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
tmpfs file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
.It Va allow.mount.zfs
|
|
privileged users inside the jail will be able to mount and unmount the
|
|
ZFS file system.
|
|
This permission is effective only together with
|
|
.Va allow.mount
|
|
and only when
|
|
.Va enforce_statfs
|
|
is set to a value lower than 2.
|
|
See
|
|
.Xr zfs 8
|
|
for information on how to configure the ZFS filesystem to operate from
|
|
within a jail.
|
|
.It Va allow.vmm
|
|
The jail may access
|
|
.Xr vmm 4 .
|
|
This flag is only available when the
|
|
.Xr vmm 4
|
|
kernel module is loaded.
|
|
.It Va linux
|
|
Determine how a jail's Linux emulation environment appears.
|
|
A value of
|
|
.Dq inherit
|
|
will keep the same environment, and
|
|
.Dq new
|
|
will give the jail its own environment (still originally inherited when
|
|
the jail is created).
|
|
.It Va linux.osname , linux.osrelease , linux.oss_version
|
|
The Linux OS name, OS release, and OSS version associated with this jail.
|
|
.It Va sysvmsg
|
|
Allow access to SYSV IPC message primitives.
|
|
If set to
|
|
.Dq inherit ,
|
|
all IPC objects on the system are visible to this jail, whether they
|
|
were created by the jail itself, the base system, or other jails.
|
|
If set to
|
|
.Dq new ,
|
|
the jail will have its own key namespace, and can only see the objects
|
|
that it has created;
|
|
the system (or parent jail) has access to the jail's objects, but not to
|
|
its keys.
|
|
If set to
|
|
.Dq disable ,
|
|
the jail cannot perform any sysvmsg-related system calls.
|
|
.It Va sysvsem, sysvshm
|
|
Allow access to SYSV IPC semaphore and shared memory primitives, in the
|
|
same manner as
|
|
.Va sysvmsg.
|
|
.El
|
|
.Pp
|
|
There are pseudo-parameters that are not passed to the kernel, but are
|
|
used by
|
|
.Nm
|
|
to set up the jail environment, often by running specified commands
|
|
when jails are created or removed.
|
|
The
|
|
.Va exec.*
|
|
command parameters are
|
|
.Xr sh 1
|
|
command lines that are run in either the system or jail environment.
|
|
They may be given multiple values, which would run the specified
|
|
commands in sequence.
|
|
All commands must succeed (return a zero exit status), or the jail will
|
|
not be created or removed, as appropriate.
|
|
.Pp
|
|
The pseudo-parameters are:
|
|
.Bl -tag -width indent
|
|
.It Va exec.prepare
|
|
Command(s) to run in the system environment to prepare a jail for creation.
|
|
These commands are executed before assigning IP addresses and mounting
|
|
filesystems, so they may be used to create a new jail filesystem if it does
|
|
not already exist.
|
|
.It Va exec.prestart
|
|
Command(s) to run in the system environment before a jail is created.
|
|
.It Va exec.created
|
|
Command(s) to run in the system environment right after a jail has been
|
|
created, but before commands (or services) get executed in the jail.
|
|
.It Va exec.start
|
|
Command(s) to run in the jail environment when a jail is created.
|
|
A typical command to run is
|
|
.Dq sh /etc/rc .
|
|
.It Va command
|
|
A synonym for
|
|
.Va exec.start
|
|
for use when specifying a jail directly on the command line.
|
|
Unlike other parameters whose value is a single string,
|
|
.Va command
|
|
uses the remainder of the
|
|
.Nm
|
|
command line as its own arguments.
|
|
.It Va exec.poststart
|
|
Command(s) to run in the system environment after a jail is created,
|
|
and after any
|
|
.Va exec.start
|
|
commands have completed.
|
|
.It Va exec.prestop
|
|
Command(s) to run in the system environment before a jail is removed.
|
|
.It Va exec.stop
|
|
Command(s) to run in the jail environment before a jail is removed,
|
|
and after any
|
|
.Va exec.prestop
|
|
commands have completed.
|
|
A typical command to run is
|
|
.Dq sh /etc/rc.shutdown jail .
|
|
.It Va exec.poststop
|
|
Command(s) to run in the system environment after a jail is removed.
|
|
.It Va exec.release
|
|
Command(s) to run in the system environment after all other actions are done.
|
|
These commands are executed after unmounting filesystems and removing IP
|
|
addresses, so they may be used to remove a jail filesystem if it is no longer
|
|
needed.
|
|
.It Va exec.clean
|
|
Run commands in a clean environment.
|
|
The environment is discarded except for
|
|
.Ev HOME , SHELL , TERM
|
|
and
|
|
.Ev USER .
|
|
.Ev HOME
|
|
and
|
|
.Ev SHELL
|
|
are set to the target login's default values.
|
|
.Ev USER
|
|
is set to the target login.
|
|
.Ev TERM
|
|
is imported from the current environment.
|
|
The environment variables from the login class capability database for the
|
|
target login are also set.
|
|
.It Va exec.jail_user
|
|
The user to run commands as, when running in the jail environment.
|
|
The default is to run the commands as the current user.
|
|
.It Va exec.system_jail_user
|
|
This boolean option looks for the
|
|
.Va exec.jail_user
|
|
in the system
|
|
.Xr passwd 5
|
|
file, instead of in the jail's file.
|
|
.It Va exec.system_user
|
|
The user to run commands as, when running in the system environment.
|
|
The default is to run the commands as the current user.
|
|
.It Va exec.timeout
|
|
The maximum amount of time to wait for a command to complete, in
|
|
seconds.
|
|
If a command is still running after this timeout has passed,
|
|
the jail will not be created or removed, as appropriate.
|
|
.It Va exec.consolelog
|
|
A file to direct command output (stdout and stderr) to.
|
|
.It Va exec.fib
|
|
The FIB (routing table) to set when running commands inside the jail.
|
|
.It Va stop.timeout
|
|
The maximum amount of time to wait for a jail's processes to exit
|
|
after sending them a
|
|
.Dv SIGTERM
|
|
signal (which happens after the
|
|
.Va exec.stop
|
|
commands have completed).
|
|
After this many seconds have passed, the jail will be removed, which
|
|
will kill any remaining processes.
|
|
If this is set to zero, no
|
|
.Dv SIGTERM
|
|
is sent and the jail is immediately removed.
|
|
The default is 10 seconds.
|
|
.It Va interface
|
|
A network interface to add the jail's IP addresses
|
|
.Va ( ip4.addr
|
|
and
|
|
.Va ip6.addr )
|
|
to.
|
|
An alias for each address will be added to the interface before the
|
|
jail is created, and will be removed from the interface after the
|
|
jail is removed.
|
|
.It Va ip4.addr
|
|
In addition to the IP addresses that are passed to the kernel, an
|
|
interface, netmask and additional parameters (as supported by
|
|
.Xr ifconfig 8 Ns )
|
|
may also be specified, in the form
|
|
.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar netmask param ... .
|
|
If an interface is given before the IP address, an alias for the address
|
|
will be added to that interface, as it is with the
|
|
.Va interface
|
|
parameter.
|
|
If a netmask in either dotted-quad or CIDR form is given
|
|
after an IP address, it will be used when adding the IP alias.
|
|
If additional parameters are specified then they will also be used when
|
|
adding the IP alias.
|
|
.It Va ip6.addr
|
|
In addition to the IP addresses that are passed to the kernel,
|
|
an interface, prefix and additional parameters (as supported by
|
|
.Xr ifconfig 8 Ns )
|
|
may also be specified, in the form
|
|
.Dq Ar interface Ns | Ns Ar ip-address Ns / Ns Ar prefix param ... .
|
|
.It Va vnet.interface
|
|
A network interface to give to a vnet-enabled jail after is it created.
|
|
The interface will automatically be released when the jail is removed.
|
|
.It Va ip_hostname
|
|
Resolve the
|
|
.Va host.hostname
|
|
parameter and add all IP addresses returned by the resolver
|
|
to the list of addresses
|
|
.Po Va ip4.addr
|
|
or
|
|
.Va ip6.addr Pc
|
|
for this jail.
|
|
This may affect default address selection for outgoing IPv4 connections
|
|
from jails.
|
|
The address first returned by the resolver for each address family
|
|
will be used as the primary address.
|
|
.It Va mount
|
|
A filesystem to mount before creating the jail (and to unmount after
|
|
removing it), given as a single
|
|
.Xr fstab 5
|
|
line.
|
|
.It Va mount.fstab
|
|
An
|
|
.Xr fstab 5
|
|
format file containing filesystems to mount before creating a jail.
|
|
.It Va mount.devfs
|
|
Mount a
|
|
.Xr devfs 5
|
|
filesystem on the chrooted
|
|
.Pa /dev
|
|
directory, and apply the ruleset in the
|
|
.Va devfs_ruleset
|
|
parameter (or a default of ruleset 4: devfsrules_jail)
|
|
to restrict the devices visible inside the jail.
|
|
.It Va mount.fdescfs
|
|
Mount a
|
|
.Xr fdescfs 5
|
|
filesystem on the chrooted
|
|
.Pa /dev/fd
|
|
directory.
|
|
.It Va mount.procfs
|
|
Mount a
|
|
.Xr procfs 5
|
|
filesystem on the chrooted
|
|
.Pa /proc
|
|
directory.
|
|
.It Va allow.dying
|
|
Allow making changes to a
|
|
.Va dying
|
|
jail.
|
|
.It Va depend
|
|
Specify a jail (or jails) that this jail depends on.
|
|
When this jail is to be created, any jail(s) it depends on must already exist.
|
|
If not, they will be created automatically, up to the completion of the last
|
|
.Va exec.poststart
|
|
command, before any action will taken to create this jail.
|
|
When jails are removed the opposite is true:
|
|
this jail will be removed, up to the last
|
|
.Va exec.poststop
|
|
command, before any jail(s) it depends on are stopped.
|
|
.El
|
|
.Sh EXAMPLES
|
|
Jails are typically set up using one of two philosophies: either to
|
|
constrain a specific application (possibly running with privilege), or
|
|
to create a
|
|
.Dq "virtual system image"
|
|
running a variety of daemons and services.
|
|
In both cases, a fairly complete file system install of
|
|
.Fx
|
|
is
|
|
required, so as to provide the necessary command line tools, daemons,
|
|
libraries, application configuration files, etc.
|
|
However, for a virtual server configuration, a fair amount of
|
|
additional work is required so as to replace the
|
|
.Dq boot
|
|
process.
|
|
This manual page documents the configuration steps necessary to support
|
|
either of these steps, although the configuration steps may need to be
|
|
refined based on local requirements.
|
|
.Ss "Setting up a Jail Directory Tree"
|
|
To set up a jail directory tree containing an entire
|
|
.Fx
|
|
distribution, the following
|
|
.Xr sh 1
|
|
command script can be used:
|
|
.Bd -literal -offset indent
|
|
D=/here/is/the/jail
|
|
cd /usr/src
|
|
mkdir -p $D
|
|
make world DESTDIR=$D
|
|
make distribution DESTDIR=$D
|
|
.Ed
|
|
.Pp
|
|
In many cases this example would put far more in the jail than needed.
|
|
In the other extreme case a jail might contain only one file:
|
|
the executable to be run in the jail.
|
|
.Pp
|
|
We recommend experimentation, and caution that it is a lot easier to
|
|
start with a
|
|
.Dq fat
|
|
jail and remove things until it stops working,
|
|
than it is to start with a
|
|
.Dq thin
|
|
jail and add things until it works.
|
|
.Ss "Setting Up a Jail"
|
|
Do what was described in
|
|
.Sx "Setting Up a Jail Directory Tree"
|
|
to build the jail directory tree.
|
|
For the sake of this example, we will
|
|
assume you built it in
|
|
.Pa /data/jail/testjail ,
|
|
for a jail named
|
|
.Dq testjail .
|
|
Substitute below as needed with your
|
|
own directory, IP address, and hostname.
|
|
.Ss "Setting up the Host Environment"
|
|
First, set up the real system's environment to be
|
|
.Dq jail-friendly .
|
|
For consistency, we will refer to the parent box as the
|
|
.Dq "host environment" ,
|
|
and to the jailed virtual machine as the
|
|
.Dq "jail environment" .
|
|
Since jails are implemented using IP aliases, one of the first things to do
|
|
is to disable IP services on the host system that listen on all local
|
|
IP addresses for a service.
|
|
If a network service is present in the host environment that binds all
|
|
available IP addresses rather than specific IP addresses, it may service
|
|
requests sent to jail IP addresses if the jail did not bind the port.
|
|
This means changing
|
|
.Xr inetd 8
|
|
to only listen on the
|
|
appropriate IP address, and so forth.
|
|
Add the following to
|
|
.Pa /etc/rc.conf
|
|
in the host environment:
|
|
.Bd -literal -offset indent
|
|
sendmail_enable="NO"
|
|
inetd_flags="-wW -a 192.0.2.23"
|
|
rpcbind_enable="NO"
|
|
.Ed
|
|
.Pp
|
|
.Li 192.0.2.23
|
|
is the native IP address for the host system, in this example.
|
|
Daemons that run out of
|
|
.Xr inetd 8
|
|
can be easily configured to use only the specified host IP address.
|
|
Other daemons
|
|
will need to be manually configured \(em for some this is possible through
|
|
.Xr rc.conf 5
|
|
flags entries; for others it is necessary to modify per-application
|
|
configuration files, or to recompile the application.
|
|
The following frequently deployed services must have their individual
|
|
configuration files modified to limit the application to listening
|
|
to a specific IP address:
|
|
.Pp
|
|
To configure
|
|
.Xr sshd 8 ,
|
|
it is necessary to modify
|
|
.Pa /etc/ssh/sshd_config .
|
|
.Pp
|
|
To configure
|
|
.Xr sendmail 8 ,
|
|
it is necessary to modify
|
|
.Pa /etc/mail/sendmail.cf .
|
|
.Pp
|
|
In addition, a number of services must be recompiled in order to run
|
|
them in the host environment.
|
|
This includes most applications providing services using
|
|
.Xr rpc 3 ,
|
|
such as
|
|
.Xr rpcbind 8 ,
|
|
.Xr nfsd 8 ,
|
|
and
|
|
.Xr mountd 8 .
|
|
In general, applications for which it is not possible to specify which
|
|
IP address to bind should not be run in the host environment unless they
|
|
should also service requests sent to jail IP addresses.
|
|
Attempting to serve
|
|
NFS from the host environment may also cause confusion, and cannot be
|
|
easily reconfigured to use only specific IPs, as some NFS services are
|
|
hosted directly from the kernel.
|
|
Any third-party network software running
|
|
in the host environment should also be checked and configured so that it
|
|
does not bind all IP addresses, which would result in those services also
|
|
appearing to be offered by the jail environments.
|
|
.Pp
|
|
Once
|
|
these daemons have been disabled or fixed in the host environment, it is
|
|
best to reboot so that all daemons are in a known state, to reduce the
|
|
potential for confusion later (such as finding that when you send mail
|
|
to a jail, and its sendmail is down, the mail is delivered to the host,
|
|
etc.).
|
|
.Ss "Configuring the Jail"
|
|
Start any jail for the first time without configuring the network
|
|
interface so that you can clean it up a little and set up accounts.
|
|
As
|
|
with any machine (virtual or not), you will need to set a root password, time
|
|
zone, etc.
|
|
Some of these steps apply only if you intend to run a full virtual server
|
|
inside the jail; others apply both for constraining a particular application
|
|
or for running a virtual server.
|
|
.Pp
|
|
Start a shell in the jail:
|
|
.Bd -literal -offset indent
|
|
jail -c path=/data/jail/testjail mount.devfs \\
|
|
host.hostname=testhostname ip4.addr=192.0.2.100 \\
|
|
command=/bin/sh
|
|
.Ed
|
|
.Pp
|
|
Assuming no errors, you will end up with a shell prompt within the jail.
|
|
You can now run
|
|
.Xr bsdconfig 8
|
|
and do the post-install configuration to set various configuration options,
|
|
or perform these actions manually by editing
|
|
.Pa /etc/rc.conf ,
|
|
etc.
|
|
.Pp
|
|
.Bl -bullet -offset indent -compact
|
|
.It
|
|
Configure
|
|
.Pa /etc/resolv.conf
|
|
so that name resolution within the jail will work correctly.
|
|
.It
|
|
Run
|
|
.Xr newaliases 1
|
|
to quell
|
|
.Xr sendmail 8
|
|
warnings.
|
|
.It
|
|
Set a root password, probably different from the real host system.
|
|
.It
|
|
Set the timezone.
|
|
.It
|
|
Add accounts for users in the jail environment.
|
|
.It
|
|
Install any packages the environment requires.
|
|
.El
|
|
.Pp
|
|
You may also want to perform any package-specific configuration (web servers,
|
|
SSH servers, etc), patch up
|
|
.Pa /etc/syslog.conf
|
|
so it logs as you would like, etc.
|
|
If you are not using a virtual server, you may wish to modify
|
|
.Xr syslogd 8
|
|
in the host environment to listen on the syslog socket in the jail
|
|
environment; in this example, the syslog socket would be stored in
|
|
.Pa /data/jail/testjail/var/run/log .
|
|
.Pp
|
|
Exit from the shell, and the jail will be shut down.
|
|
.Ss "Starting the Jail"
|
|
You are now ready to restart the jail and bring up the environment with
|
|
all of its daemons and other programs.
|
|
Create an entry for the jail in
|
|
.Pa /etc/jail.conf :
|
|
.Bd -literal -offset indent
|
|
testjail {
|
|
path = /tmp/jail/testjail;
|
|
mount.devfs;
|
|
host.hostname = testhostname;
|
|
ip4.addr = 192.0.2.100;
|
|
interface = em0;
|
|
exec.start = "/bin/sh /etc/rc";
|
|
exec.stop = "/bin/sh /etc/rc.shutdown jail";
|
|
}
|
|
.Ed
|
|
.Pp
|
|
To start a virtual server environment,
|
|
.Pa /etc/rc
|
|
is run to launch various daemons and services, and
|
|
.Pa /etc/rc.shutdown
|
|
is run to shut them down when the jail is removed.
|
|
If you are running a single application in the jail,
|
|
substitute the command used to start the application for
|
|
.Dq /bin/sh /etc/rc ;
|
|
there may be some script available to cleanly shut down the application,
|
|
or it may be sufficient to go without a stop command, and have
|
|
.Nm
|
|
send
|
|
.Dv SIGTERM
|
|
to the application.
|
|
.Pp
|
|
Start the jail by running:
|
|
.Bd -literal -offset indent
|
|
jail -c testjail
|
|
.Ed
|
|
.Pp
|
|
A few warnings may be produced; however, it should all work properly.
|
|
You should be able to see
|
|
.Xr inetd 8 ,
|
|
.Xr syslogd 8 ,
|
|
and other processes running within the jail using
|
|
.Xr ps 1 ,
|
|
with the
|
|
.Ql J
|
|
flag appearing beside jailed processes.
|
|
To see an active list of jails, use
|
|
.Xr jls 8 .
|
|
If
|
|
.Xr sshd 8
|
|
is enabled in the jail environment, you should be able to
|
|
.Xr ssh 1
|
|
to the hostname or IP address of the jailed environment, and log
|
|
in using the accounts you created previously.
|
|
.Pp
|
|
It is possible to have jails started at boot time.
|
|
Please refer to the
|
|
.Dq jail_*
|
|
variables in
|
|
.Xr rc.conf 5
|
|
for more information.
|
|
.Ss "Managing the Jail"
|
|
Normal machine shutdown commands, such as
|
|
.Xr halt 8 ,
|
|
.Xr reboot 8 ,
|
|
and
|
|
.Xr shutdown 8 ,
|
|
cannot be used successfully within the jail.
|
|
To kill all processes from within a jail, you may use one of the
|
|
following commands, depending on what you want to accomplish:
|
|
.Bd -literal -offset indent
|
|
kill -TERM -1
|
|
kill -KILL -1
|
|
.Ed
|
|
.Pp
|
|
This will send the
|
|
.Dv SIGTERM
|
|
or
|
|
.Dv SIGKILL
|
|
signals to all processes in the jail \(em be careful not to run this from
|
|
the host environment!
|
|
Once all of the jail's processes have died, unless the jail was created
|
|
with the
|
|
.Va persist
|
|
parameter, the jail will be removed.
|
|
Depending on
|
|
the intended use of the jail, you may also want to run
|
|
.Pa /etc/rc.shutdown
|
|
from within the jail.
|
|
.Pp
|
|
To shut down the jail from the outside, simply remove it with:
|
|
.Bd -literal -offset indent
|
|
jail -r
|
|
.Ed
|
|
.Pp
|
|
which will run any commands specified by
|
|
.Va exec.stop ,
|
|
and then send
|
|
.Dv SIGTERM
|
|
and eventually
|
|
.Dv SIGKILL
|
|
to any remaining jailed processes.
|
|
.Pp
|
|
The
|
|
.Pa /proc/ Ns Ar pid Ns Pa /status
|
|
file contains, as its last field, the name of the jail in which the
|
|
process runs, or
|
|
.Dq Li -
|
|
to indicate that the process is not running within a jail.
|
|
The
|
|
.Xr ps 1
|
|
command also shows a
|
|
.Ql J
|
|
flag for processes in a jail.
|
|
.Pp
|
|
You can also list/kill processes based on their jail ID.
|
|
To show processes and their jail ID, use the following command:
|
|
.Pp
|
|
.Dl "ps ax -o pid,jid,args"
|
|
.Pp
|
|
To show and then kill processes in jail number 3 use the following commands:
|
|
.Bd -literal -offset indent
|
|
pgrep -lfj 3
|
|
pkill -j 3
|
|
.Ed
|
|
or:
|
|
.Pp
|
|
.Dl "killall -j 3"
|
|
.Ss "Jails and File Systems"
|
|
It is not possible to
|
|
.Xr mount 8
|
|
or
|
|
.Xr umount 8
|
|
any file system inside a jail unless the file system is marked
|
|
jail-friendly, the jail's
|
|
.Va allow.mount
|
|
parameter is set, and the jail's
|
|
.Va enforce_statfs
|
|
parameter is lower than 2.
|
|
.Pp
|
|
Multiple jails sharing the same file system can influence each other.
|
|
For example, a user in one jail can fill the file system,
|
|
leaving no space for processes in the other jail.
|
|
Trying to use
|
|
.Xr quota 1
|
|
to prevent this will not work either, as the file system quotas
|
|
are not aware of jails but only look at the user and group IDs.
|
|
This means the same user ID in two jails share a single file
|
|
system quota.
|
|
One would need to use one file system per jail to make this work.
|
|
.Ss "Sysctl MIB Entries"
|
|
The read-only entry
|
|
.Va security.jail.jailed
|
|
can be used to determine if a process is running inside a jail (value
|
|
is one) or not (value is zero).
|
|
.Pp
|
|
The variable
|
|
.Va security.jail.max_af_ips
|
|
determines how may address per address family a jail may have.
|
|
The default is 255.
|
|
.Pp
|
|
Some MIB variables have per-jail settings.
|
|
Changes to these variables by a jailed process do not affect the host
|
|
environment, only the jail environment.
|
|
These variables are
|
|
.Va kern.securelevel ,
|
|
.Va security.bsd.suser_enabled ,
|
|
.Va kern.hostname ,
|
|
.Va kern.domainname ,
|
|
.Va kern.hostid ,
|
|
and
|
|
.Va kern.hostuuid .
|
|
.Ss "Hierarchical Jails"
|
|
By setting a jail's
|
|
.Va children.max
|
|
parameter, processes within a jail may be able to create jails of their own.
|
|
These child jails are kept in a hierarchy, with jails only able to see and/or
|
|
modify the jails they created (or those jails' children).
|
|
Each jail has a read-only
|
|
.Va parent
|
|
parameter, containing the
|
|
.Va jid
|
|
of the jail that created it; a
|
|
.Va jid
|
|
of 0 indicates the jail is a child of the current jail (or is a top-level
|
|
jail if the current process isn't jailed).
|
|
.Pp
|
|
Jailed processes are not allowed to confer greater permissions than they
|
|
themselves are given, e.g., if a jail is created with
|
|
.Va allow.nomount ,
|
|
it is not able to create a jail with
|
|
.Va allow.mount
|
|
set.
|
|
Similarly, such restrictions as
|
|
.Va ip4.addr
|
|
and
|
|
.Va securelevel
|
|
may not be bypassed in child jails.
|
|
.Pp
|
|
A child jail may in turn create its own child jails if its own
|
|
.Va children.max
|
|
parameter is set (remember it is zero by default).
|
|
These jails are visible to and can be modified by their parent and all
|
|
ancestors.
|
|
.Pp
|
|
Jail names reflect this hierarchy, with a full name being an MIB-type string
|
|
separated by dots.
|
|
For example, if a base system process creates a jail
|
|
.Dq foo ,
|
|
and a process under that jail creates another jail
|
|
.Dq bar ,
|
|
then the second jail will be seen as
|
|
.Dq foo.bar
|
|
in the base system (though it is only seen as
|
|
.Dq bar
|
|
to any processes inside jail
|
|
.Dq foo ) .
|
|
Jids on the other hand exist in a single space, and each jail must have a
|
|
unique jid.
|
|
.Pp
|
|
Like the names, a child jail's
|
|
.Va path
|
|
appears relative to its creator's own
|
|
.Va path .
|
|
This is by virtue of the child jail being created in the chrooted
|
|
environment of the first jail.
|
|
.Sh SEE ALSO
|
|
.Xr killall 1 ,
|
|
.Xr lsvfs 1 ,
|
|
.Xr newaliases 1 ,
|
|
.Xr pgrep 1 ,
|
|
.Xr pkill 1 ,
|
|
.Xr ps 1 ,
|
|
.Xr quota 1 ,
|
|
.Xr jail_set 2 ,
|
|
.Xr vmm 4 ,
|
|
.Xr devfs 5 ,
|
|
.Xr fdescfs 5 ,
|
|
.Xr jail.conf 5 ,
|
|
.Xr linprocfs 5 ,
|
|
.Xr linsysfs 5 ,
|
|
.Xr procfs 5 ,
|
|
.Xr rc.conf 5 ,
|
|
.Xr sysctl.conf 5 ,
|
|
.Xr bsdconfig 8 ,
|
|
.Xr chroot 8 ,
|
|
.Xr devfs 8 ,
|
|
.Xr halt 8 ,
|
|
.Xr ifconfig 8 ,
|
|
.Xr inetd 8 ,
|
|
.Xr jexec 8 ,
|
|
.Xr jls 8 ,
|
|
.Xr mount 8 ,
|
|
.Xr reboot 8 ,
|
|
.Xr rpcbind 8 ,
|
|
.Xr sendmail 8 ,
|
|
.Xr shutdown 8 ,
|
|
.Xr sysctl 8 ,
|
|
.Xr syslogd 8 ,
|
|
.Xr umount 8
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
utility appeared in
|
|
.Fx 4.0 .
|
|
Hierarchical/extensible jails were introduced in
|
|
.Fx 8.0 .
|
|
The configuration file was introduced in
|
|
.Fx 9.1 .
|
|
.Sh AUTHORS
|
|
.An -nosplit
|
|
The jail feature was written by
|
|
.An Poul-Henning Kamp
|
|
for R&D Associates
|
|
who contributed it to
|
|
.Fx .
|
|
.Pp
|
|
.An Robert Watson
|
|
wrote the extended documentation, found a few bugs, added
|
|
a few new features, and cleaned up the userland jail environment.
|
|
.Pp
|
|
.An Bjoern A. Zeeb
|
|
added multi-IP jail support for IPv4 and IPv6 based on a patch
|
|
originally done by
|
|
.An Pawel Jakub Dawidek
|
|
for IPv4.
|
|
.Pp
|
|
.An James Gritton
|
|
added the extensible jail parameters, hierarchical jails,
|
|
and the configuration file.
|
|
.Sh BUGS
|
|
It might be a good idea to add an
|
|
address alias flag such that daemons listening on all IPs
|
|
.Pq Dv INADDR_ANY
|
|
will not bind on that address, which would facilitate building a safe
|
|
host environment such that host daemons do not impose on services offered
|
|
from within jails.
|
|
Currently, the simplest answer is to minimize services
|
|
offered on the host, possibly limiting it to services offered from
|
|
.Xr inetd 8
|
|
which is easily configurable.
|
|
.Sh NOTES
|
|
Great care should be taken when managing directories visible within the jail.
|
|
For example, if a jailed process has its current working directory set to a
|
|
directory that is moved out of the jail's chroot, then the process may gain
|
|
access to the file space outside of the jail.
|
|
It is recommended that directories always be copied, rather than moved, out
|
|
of a jail.
|
|
.Pp
|
|
In addition, there are several ways in which an unprivileged user
|
|
outside the jail can cooperate with a privileged user inside the jail
|
|
and thereby obtain elevated privileges in the host environment.
|
|
Most of these attacks can be mitigated by ensuring that the jail root
|
|
is not accessible to unprivileged users in the host environment.
|
|
Regardless, as a general rule, untrusted users with privileged access
|
|
to a jail should not be given access to the host environment.
|