285 lines
7.5 KiB
Groff
285 lines
7.5 KiB
Groff
.\" $NetBSD: swapctl.2,v 1.38 2011/04/28 11:58:50 wiz 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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.\"
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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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.\" 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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.Dd May 17, 2010
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.Dt SWAPCTL 2
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.Os
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.Sh NAME
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.Nm swapctl
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.Nd modify swap configuration
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.In sys/swap.h
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.Ft int
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.Fn swapctl "int cmd" "void *arg" "int misc"
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.Sh DESCRIPTION
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The
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.Nm
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function is used to add and delete swap devices, and modify their
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configuration.
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.Pp
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The
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.Fa cmd
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parameter specifies the operation to be performed.
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The
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.Fa arg
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and
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.Fa misc
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parameters have different meanings, depending on the
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.Fa cmd
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parameter.
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.Bl -enum -offset indent
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_NSWAP ,
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the current number of swap devices in the system is returned.
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The
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.Fa arg
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and
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.Fa misc
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parameters are ignored.
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_STATS ,
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the current statistics for swap devices are returned in the
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.Fa arg
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parameter.
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No more than
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.Fa misc
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swap devices are returned.
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The
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.Fa arg
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parameter should point to an array of at least
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.Fa misc
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struct swapent structures:
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.Bd -literal
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struct swapent {
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dev_t se_dev; /* device id */
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int se_flags; /* entry flags */
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int se_nblks; /* total blocks */
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int se_inuse; /* blocks in use */
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int se_priority; /* priority */
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char se_path[PATH_MAX+1]; /* path to entry */
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};
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.Ed
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.Pp
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The flags are defined as
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.Bd -literal
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SWF_INUSE in use: we have swapped here
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SWF_ENABLE enabled: we can swap here
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SWF_BUSY busy: I/O happening here
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SWF_FAKE fake: still being built
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.Ed
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_ON ,
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the
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.Fa arg
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parameter is used as a pathname of a file to enable swapping to.
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The
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.Fa misc
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parameter is used to set the priority of this swap device.
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_OFF ,
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the
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.Fa arg
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parameter is used as the pathname of a file to disable swapping from.
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The
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.Fa misc
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parameter is ignored.
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_CTL ,
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the
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.Fa arg
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and
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.Fa misc
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parameters have the same function as for the
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.Dv SWAP_ON
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case, except that they change the priority of a currently enabled swap device.
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_DUMPDEV ,
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the
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.Fa arg
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parameter is used as the pathname of a device to use as the dump device,
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should the system panic.
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.It
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If
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.Fa cmd
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is
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.Dv SWAP_GETDUMPDEV ,
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the
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.Fa arg
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parameter points to a dev_t, which is filled in by the current dump device.
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.El
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.Pp
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When swapping is enabled on a block device, the first portion of the disk is
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left unused to prevent any disklabel present from being overwritten.
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This space is allocated from the swap device when the
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.Dv SWAP_ON
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command is used.
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.Pp
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The priority of a swap device can be used to fill faster swap devices before
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slower ones.
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A priority of 0 is the highest, with larger numbers having lower priority.
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For a fuller discussion on swap priority, see the
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.Sx SWAP PRIORITY
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section in
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.Xr swapctl 8 .
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.Sh RETURN VALUES
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If the
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.Fa cmd
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parameter is
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.Dv SWAP_NSWAP
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or
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.Dv SWAP_STATS ,
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.Fn swapctl
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returns the number of swap devices, if successful.
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The
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.Dv SWAP_NSWAP
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command is always successful.
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Otherwise it returns 0 on success and \-1
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on failure, setting the global variable
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.Va errno
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to indicate the error.
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.Sh ERRORS
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.Fn swapctl
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succeeds unless:
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.Bl -tag -width Er
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.It Bq Er EACCES
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Search permission is denied for a component of the path prefix.
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.It Bq Er EBUSY
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The device specified by
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.Fa arg
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has already been made available for swapping.
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.It Bq Er EFAULT
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.Fa arg
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points outside the process' allocated address space.
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.It Bq Er EINVAL
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The device configured by
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.Fa arg
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has no associated size, or the
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.Fa cmd
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was unknown.
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.It Bq Er EIO
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An I/O error occurred while opening the swap device.
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.It Bq Er ELOOP
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Too many symbolic links were encountered in translating the pathname.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Brq Dv NAME_MAX
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characters, or an entire path name exceeded
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.Brq Dv PATH_MAX
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characters.
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.It Bq Er ENOENT
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The named device does not exist.
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For the
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.Dv SWAP_CTL
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command, the named device is not currently enabled for swapping.
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.It Bq Er ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENXIO
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The major device number of
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.Fa arg
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is out of range (this indicates no device driver exists
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for the associated hardware); or
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the block device specified by
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.Fa arg
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is not marked as a swap partition in the disklabel.
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.It Bq Er EPERM
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The caller is not the super-user.
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.El
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.Sh SEE ALSO
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.Xr swapctl 8
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.Sh HISTORY
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The
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.Fn swapctl
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function call appeared in
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.Nx 1.3 .
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The
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.Fa se_path
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member was added to
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.Va struct swapent
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in
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.Nx 1.4 ,
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when the header file was also moved from
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.In vm/vm_swap.h
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to its current location in
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.In sys/swap.h .
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.Sh AUTHORS
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The current swap system was designed and implemented by
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Matthew Green
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.Aq mrg@eterna.com.au ,
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with help from Paul Kranenburg
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.Aq pk@NetBSD.org
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and Leo Weppelman
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.Aq leo@NetBSD.org ,
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and insights from Jason R. Thorpe
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.Aq thorpej@NetBSD.org .
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