243 lines
5.6 KiB
Groff
243 lines
5.6 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. 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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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93
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.\"
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.Dd November 29, 2021
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.Dt SWAPON 8
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.Os
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.Sh NAME
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.Nm swapon , swapoff , swapctl
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.Nd "specify devices for paging and swapping"
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.Sh SYNOPSIS
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.Nm swapon
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.Oo Fl F Ar fstab
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.Oc
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.Fl aLq | E Ar
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.Nm swapoff
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.Oo Fl F Ar fstab
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.Oc
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.Fl afLq | Ar
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.Nm swapctl
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.Op Fl AfghklmsU
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.Oo
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.Fl a Ar
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.Fl d Ar
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.Oc
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.Sh DESCRIPTION
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The
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.Nm swapon , swapoff
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and
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.Nm swapctl
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utilities are used to control swap devices in the system.
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At boot time all swap entries in
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.Pa /etc/fstab
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are added automatically when the system goes multi-user.
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Swap devices use a fixed interleave; the maximum number of devices
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is unlimited.
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There is no priority mechanism.
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.Pp
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The
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.Nm swapon
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utility adds the specified swap devices to the system.
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If the
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.Fl a
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option is used, all swap devices in
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.Pa /etc/fstab
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will be added, unless their
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.Dq noauto
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or
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.Dq late
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option is also set.
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If the
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.Fl L
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option is specified,
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swap devices with the
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.Dq late
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option will be added as well as ones with no option.
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If the
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.Fl q
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option is used,
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informational messages will not be
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written to standard output when a swap device is added.
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The
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.Fl E
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option causes each of following devices to receive a
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.Dv BIO_DELETE
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command.
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This command marks the device's blocks as unused, except those that
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might store a disk label.
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This marking can erase a crash dump.
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To delay
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.Nm swapon
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for a device until after
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.Nm savecore
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has copied the crash dump to another location, use the
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.Dq late
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option.
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.Pp
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The
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.Nm swapoff
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utility removes the specified swap devices from the system.
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If the
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.Fl a
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option is used, all swap devices in
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.Pa /etc/fstab
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will be removed, unless their
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.Dq noauto
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option is also set.
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If the
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.Fl L
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option is specified,
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only swap devices with the
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.Dq late
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option will be removed.
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If the
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.Fl q
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option is used,
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informational messages will not be
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written to standard output when a swap device is removed.
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Note that
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.Nm swapoff
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will fail and refuse to remove a swap device if a very conservative
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check does not conclude that there is sufficient VM (memory +
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remaining swap devices) to run the system.
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The
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.Fl f
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option turns off this check, which could deadlock the system
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if there is insufficient swap space remaining.
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.Pp
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The
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.Nm swapoff
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utility
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must move swapped pages out of the device being removed which could
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lead to high system loads for a period of time, depending on how
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much data has been swapped out to that device.
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.Pp
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Other options supported by both
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.Nm swapon
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and
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.Nm swapoff
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are as follows:
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.Bl -tag -width indent
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.It Fl F Ar fstab
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Specify the
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.Pa fstab
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file to use (in conjunction with
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.Fl a Ns ).
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.El
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.Pp
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The
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.Nm swapctl
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utility exists primarily for those familiar with other
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.Bx Ns s
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and may be
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used to add, remove, or list swap devices.
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Note that the
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.Fl a
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option is used differently in
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.Nm swapctl
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and indicates that a specific list of devices should be added.
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The
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.Fl d
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option indicates that a specific list should be removed.
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The
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.Fl A
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and
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.Fl U
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options to
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.Nm swapctl
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operate on all swap entries in
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.Pa /etc/fstab
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which do not have their
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.Dq noauto
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option set.
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.Pp
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Swap information can be generated using the
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.Xr swapinfo 8
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utility,
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.Nm pstat
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.Fl s ,
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or
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.Nm swapctl
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.Fl l .
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The
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.Nm swapctl
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utility has the following options for listing swap:
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.Bl -tag -width indent
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.It Fl h
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Output values in human-readable form.
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.It Fl g
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Output values in gigabytes.
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.It Fl k
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Output values in kilobytes.
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.It Fl m
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Output values in megabytes.
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.It Fl l
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List the devices making up system swap.
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.It Fl s
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Print a summary line for system swap.
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.Pp
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The
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.Ev BLOCKSIZE
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environment variable is used if not specifically
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overridden.
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512 byte blocks are used by default.
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.El
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.Sh FILES
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.Bl -tag -width ".Pa /dev/{ada,da}?s?b" -compact
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.It Pa /dev/{ada,da}?s?b
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standard paging devices
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.It Pa /dev/md?
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memory disk devices
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.It Pa /etc/fstab
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.Tn ASCII
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file system description table
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.El
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.Sh DIAGNOSTICS
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These utilities may fail for the reasons described in
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.Xr swapon 2 .
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.Sh SEE ALSO
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.Xr swapon 2 ,
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.Xr fstab 5 ,
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.Xr init 8 ,
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.Xr mdconfig 8 ,
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.Xr pstat 8 ,
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.Xr rc 8
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.Sh HISTORY
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The
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.Nm swapon
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utility appeared in
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.Bx 4.0 .
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The
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.Nm swapoff
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and
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.Nm swapctl
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utilities appeared in
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.Fx 5.1 .
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