doc: mention mkswap long options in man page
The update will also expand kernel version numbers to have a month and year next to them. This should help users can get idea how long, for example, swap v1 has been around. [kzak@redhat.com: - modify synopsis, remove duplicate info about page size] Signed-off-by: Sami Kerola <kerolasa@iki.fi> Signed-off-by: Karel Zak <kzak@redhat.com>
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mkswap \- set up a Linux swap area
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.SH SYNOPSIS
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.B mkswap
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.RB [ \-c ]
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.RB [ \-f ]
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.RB [ \-p
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.IR PSZ ]
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.RB [ \-L
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.IR label ]
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.RB [ \-U
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.IR uuid ]
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.I device
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.RI [ size ]
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.RB [ options ]
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.IR device
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.RB [ size ]
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.SH DESCRIPTION
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.B mkswap
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sets up a Linux swap area on a device or in a file.
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@ -41,18 +34,6 @@ parameter is superfluous but retained for backwards compatibility.
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will use the entire partition or file if it is omitted.
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Specifying it is unwise -- a typo may destroy your disk.)
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The
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.I PSZ
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parameter specifies the page size to use. It is almost always
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unnecessary (even unwise) to specify it, but certain old libc
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versions lie about the page size, so it is possible that
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.B mkswap
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gets it wrong. The symptom is that a subsequent
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.B swapon
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fails because no swap signature is found. Typical values for
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.I PSZ
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are 4096 or 8192.
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After creating the swap area, you need the
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.B swapon
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command to start using it. Usually swap areas are listed in
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@ -75,12 +56,12 @@ label (SUN, BSD, ...) or on a whole disk (e.g. /dev/sda).
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.SH OPTIONS
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.TP
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.B \-c
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.BR \-c , " \-\-check"
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Check the device (if it is a block device) for bad blocks
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before creating the swap area.
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If any are found, the count is printed.
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.TP
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.B \-f
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.BR \-f , " \-\-force"
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Force -- go ahead even if the command is stupid.
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This allows the creation of a swap area larger than the file
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or partition it resides on.
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@ -90,41 +71,46 @@ Without this option,
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will refuse to erase the first block on a device with a partition table or on
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a whole disk (e.g. /dev/sda).
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.TP
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.BI \-L \ label
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.BR \-L , " \-\-label" \ device-label
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Specify a label, to allow
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.B swapon
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by label.
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.TP
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.BI \-p \ PSZ
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.BR \-p , " \-\-pagesize" \ SIZE
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Specify the page size (in bytes) to use. This option is usually unnecessary,
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.B mkswap
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reads the size from the kernel.
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.TP
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.BI \-U \ uuid
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.BR \-U , " \-\-uuid" \ UUID
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Specify the uuid to use. The default is to generate a UUID.
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.TP
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.BR \-v1
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Specify the swap-space version. The old \-v0 option has become obsolete
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and now only \-v1 is supported.
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.BR \-v , " \-\-swapversion" \ 1
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Specify the swap-space version. The old \-v 0 option has become obsolete
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and now only \-v 1 is supported.
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The kernel has not supported v0 swap-space format since 2.5.22.
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The new version v1 is supported since 2.1.117.
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The kernel has not supported v0 swap-space format since 2.5.22 (Jun 2002).
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The new version v1 is supported since 2.1.117 (Aug 1998).
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.TP
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.BR \-V , " \-\-version"
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Output version information and exit.
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.BR \-h , " \-\-help"
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Output help screen and exit.
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.SH NOTES
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The maximum useful size of a swap area depends on the architecture and
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the kernel version.
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It is roughly 2GiB on i386, PPC, m68k and ARM, 1GiB on sparc, 512MiB on mips,
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128GiB on alpha, and 3TiB on sparc64. For kernels after 2.3.3 there is no
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128GiB on alpha, and 3TiB on sparc64. For kernels after 2.3.3 (May 1999) there is no
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such limitation.
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Note that before version 2.1.117 the kernel allocated one byte for each page,
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while it now allocates two bytes, so that taking into use a swap area of 2 GiB
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might require 2 MiB of kernel memory.
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Presently, Linux allows 32 swap areas (this was 8 before Linux 2.4.10).
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Presently, Linux allows 32 swap areas (this was 8 before Linux 2.4.10 (Sep 2001)).
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The areas in use can be seen in the file
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.I /proc/swaps
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(since 2.1.25).
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(since 2.1.25 (Sep 1997)).
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.B mkswap
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refuses areas smaller than 10 pages.
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