b2b49933f4
the advertising clause. Diffs provided in PR 22396 by Joel Baker, the changes were confirmed to the board by Matt Green.
255 lines
6.2 KiB
Groff
255 lines
6.2 KiB
Groff
.\" $NetBSD: swapctl.2,v 1.28 2003/10/13 14:22:20 agc Exp $
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.\"
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.\" Copyright (c) 1997 Matthew R. Green
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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 June 20, 1997
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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" "const 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 -item -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 ENOTDIR
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A component of the path prefix is not a directory.
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.It Bq Er ENAMETOOLONG
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A component of a pathname exceeded
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.Dv NAME_MAX
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characters, or an entire path name exceeded
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.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 EACCES
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Search permission is denied for a component of the path prefix.
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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 EPERM
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The caller is not the super-user.
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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 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 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).
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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 EFAULT
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.Fa arg
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points outside the process' allocated address space.
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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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.Pa \*[Lt]vm/vm_swap.h\*[Gt] ,
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to its current location in
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.Pa \*[Lt]sys/swap.h\*[Gt] .
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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 \*[Lt]mrg@eterna.com.au\*[Gt],
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with help from Paul Kranenburg \*[Lt]pk@NetBSD.ORG\*[Gt]
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and Leo Weppelman \*[Lt]leo@NetBSD.ORG\*[Gt],
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and insights from Jason R. Thorpe \*[Lt]thorpej@NetBSD.ORG\*[Gt].
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