245 lines
6.1 KiB
Groff
245 lines
6.1 KiB
Groff
.\" $NetBSD: swapctl.8,v 1.15 1999/02/23 17:00:53 mrg Exp $
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.\"
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.\" Copyright (c) 1997 Matthew R. Green
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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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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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.\" BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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.\" AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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.\" 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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.Dd June 12, 1997
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.Dt SWAPCTL 8
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.Os NetBSD
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.Sh NAME
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.Nm swapctl ,
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.Nm swapon
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.Nd system swap management tool
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.Sh SYNOPSIS
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.Nm
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.Fl A
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.Op Fl D Ar dumpdev
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.Op Fl p Ar priority
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.Op Fl t Ar blk|noblk
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.Nm ""
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.Fl a
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.Op Fl p Ar priority
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.Ar path
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.Nm ""
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.Fl c
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.Fl p Ar priority
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.Ar path
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.Nm ""
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.Fl d
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.Ar path
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.Nm ""
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.Fl l | Fl s
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.Op Fl k
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.Nm swapon
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.Fl a | Ar path
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.Nm swapoff
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.Ar path
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.Sh DESCRIPTION
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The
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.Nm
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program adds, removes,
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lists and prioritizes swap devices and files for the system.
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The
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.Nm swapon
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program acts the same as the
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.Nm
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program, as if called with the
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.Fl a
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option, except if
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.Nm swapon
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itself is called with
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.Fl a
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in which case,
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.Nm swapon
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acts as
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.Nm
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with the
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.Fl A
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option.
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.Sh OPTIONS
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The following options are available:
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.Bl -tag -width 123456
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.It Fl A
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This option causes
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.Nm
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to read the
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.Pa /etc/fstab
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file for devices and files with a
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.Dq sw
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and
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.Dq dp
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type, and adds all these entries
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as swap devices, or for a dump device in the case of a
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.Dq dp
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type. If no swap devices are configured,
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.Nm
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will exit with an error code.
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.It Fl D
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The
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.Fl D
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option requires that a
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.Ar dumpdev
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also be in the argument list. The kernel dump device is set to
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.Ar dumpdev .
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This changed is made via the
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.Xr swapctl 2
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system call. The dump device is used when the system crashes
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to write a current snapshot of real memory, to be saved later with
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.Xr savecore 8
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at system reboot, and analyzed to determine the problem.
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.It Fl a
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The
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.Fl a
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option requires that a
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.Ar path
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also be in the argument list. The
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.Ar path
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is added to the kernel's list of swap devices using the
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.Xr swapctl 2
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system call. When using the
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.Nm swapon
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form of this command, the
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.Fl a
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option is treated the same as the
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.Fl A
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option, for backwards compatibility.
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.It Fl c
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The
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.Fl c
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option changes the priority of the listed swap device or file.
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.It Fl d
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The
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.Fl d
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option removes the listed
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.Ar path
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from the kernel's list of swap devices or files.
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.It Fl l
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The
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.Fl l
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option lists the current swap devices and files, and their usage statistics.
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.It Fl s
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The
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.Fl s
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option displays a single line summary of current swap statistics.
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.It Fl p
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The
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.Fl p
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option sets the priority of swap devices or files to the
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.Ar priority
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argument. This works with the
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.\" .Fl d ,
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.Fl a ,
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.Fl c
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and
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.Fl l
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options.
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.It Fl k
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The
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.Fl k
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option uses 1024 byte blocks instead of the default 512 byte.
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.It Fl t
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This flag modifies the function of the
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.Fl A
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option.
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The
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.Fl t
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option allows the type of device to add to be specified. An argument of
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.Ar blk
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causes all block devices in
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.Pa /etc/fstab
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to be added. An argument of
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.Ar noblk
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causes all non-block devices in
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.Pa /etc/fstab
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to be added. This option is useful in early system startup, where swapping
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may be needed before all file systems are available, such as during
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disk checks of large file systems.
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.El
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.Sh SWAP OPTIONS
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When parsing the
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.Pa /etc/fstab
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file for swap devices, the following options are recognized:
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.Pp
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.Bl -tag -width nfsmntpt=/path -compact
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.It priority=N
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This option sets the priority of the specified swap device to N. The
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highest priority is 0, second priority is 1, etc.
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.It nfsmntpt=/path
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This option is useful for swapping to NFS files. It specifies
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the local mount point to mount an NFS filesystem. Typically, once
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this mount has succeeded, the file to be used for swapping on will
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be available under this point mount. For example:
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.Bd -literal
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server:/export/swap/client none swap sw,nfsmntpt=/swap
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.Ed
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.El
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.Sh WARNINGS
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If no swap information is specified in
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.Pa /etc/fstab ,
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the system startup scripts (see
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.Xr rc 8 )
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will configure no swap space and your machine will behave very badly
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if (more likely when) it runs out of real memory.
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.Pp
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Local and remote swap files cannot be configured until after the file
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systems they reside on are mounted read/write. The system startup
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scripts need to
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.Xr fsck 8
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all local file systems before this can happen. This process requires
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substantial amounts of memory on some systems. If you configure no
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local block swap devices on a machine that has local file systems to
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check and rely only on swap files, the machine will have no swap space
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at all during system
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.Xr fsck 8
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and may run out of real memory, causing fsck to abnormally exit and
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startup scripts to fail.
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.Sh HISTORY
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The
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.Nm
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program was first made available in
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.Nx 1.3 .
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The original
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.Nm swapon
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program, provided for backwards compatibility, appeared in
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.Bx 4.0 .
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.Sh AUTHOR
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The
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.Nm
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program was written by Matthew R. Green <mrg@eterna.com.au>.
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.Sh BUGS
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The
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.Nm swapoff
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command and the
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.Fl d
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option of
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.Nm
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are not currently supported by
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.Nx .
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.Sh SEE ALSO
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.Xr swapctl 2 ,
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.Xr fstab 5 ,
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.Xr mount_nfs 8
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