173 lines
5.9 KiB
Groff
173 lines
5.9 KiB
Groff
'\" t
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.\" Title: mkswap
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.\" Author: [see the "AUTHOR(S)" section]
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.\" Generator: Asciidoctor 2.0.15
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.\" Date: 2022-05-11
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.\" Manual: System Administration
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.\" Source: util-linux 2.38.1
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.\" Language: English
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.\"
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.TH "MKSWAP" "8" "2022-05-11" "util\-linux 2.38.1" "System Administration"
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.ss \n[.ss] 0
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.nh
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.de URL
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..
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.als MTO URL
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.if \n[.g] \{\
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. mso www.tmac
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. .
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. am MTO
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. .
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. LINKSTYLE blue R < >
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.\}
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.SH "NAME"
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mkswap \- set up a Linux swap area
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.SH "SYNOPSIS"
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.sp
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\fBmkswap\fP [options] \fIdevice\fP [\fIsize\fP]
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.SH "DESCRIPTION"
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.sp
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\fBmkswap\fP sets up a Linux swap area on a device or in a file.
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.sp
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The \fIdevice\fP argument will usually be a disk partition (something like \fI/dev/sdb7\fP) but can also be a file. The Linux kernel does not look at partition IDs, but many installation scripts will assume that partitions of hex type 82 (LINUX_SWAP) are meant to be swap partitions. (\fBWarning: Solaris also uses this type. Be careful not to kill your Solaris partitions.\fP)
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.sp
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The \fIsize\fP parameter is superfluous but retained for backwards compatibility. (It specifies the desired size of the swap area in 1024\-byte blocks. \fBmkswap\fP will use the entire partition or file if it is omitted. Specifying it is unwise \- a typo may destroy your disk.)
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.sp
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After creating the swap area, you need the \fBswapon\fP(8) command to start using it. Usually swap areas are listed in \fI/etc/fstab\fP so that they can be taken into use at boot time by a \fBswapon \-a\fP command in some boot script.
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.SH "WARNING"
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.sp
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The swap header does not touch the first block. A boot loader or disk label can be there, but it is not a recommended setup. The recommended setup is to use a separate partition for a Linux swap area.
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.sp
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\fBmkswap\fP, like many others mkfs\-like utils, \fBerases the first partition block to make any previous filesystem invisible.\fP
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.sp
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However, \fBmkswap\fP refuses to erase the first block on a device with a disk label (SUN, BSD, ...).
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.SH "OPTIONS"
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.sp
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\fB\-c\fP, \fB\-\-check\fP
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.RS 4
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Check the device (if it is a block device) for bad blocks before creating the swap area. If any bad blocks are found, the count is printed.
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.RE
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.sp
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\fB\-f\fP, \fB\-\-force\fP
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.RS 4
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Go ahead even if the command is stupid. This allows the creation of a swap area larger than the file or partition it resides on.
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.sp
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Also, without this option, \fBmkswap\fP will refuse to erase the first block on a device with a partition table.
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.RE
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.sp
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\fB\-q\fP, \fB\-\-quiet\fP
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.RS 4
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Suppress output and warning messages.
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.RE
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.sp
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\fB\-L\fP, \fB\-\-label\fP \fIlabel\fP
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.RS 4
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Specify a \fIlabel\fP for the device, to allow \fBswapon\fP(8) by label.
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.RE
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.sp
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\fB\-\-lock\fP[=\fImode\fP]
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.RS 4
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Use exclusive BSD lock for device or file it operates. The optional argument \fImode\fP can be \fByes\fP, \fBno\fP (or 1 and 0) or \fBnonblock\fP. If the \fImode\fP argument is omitted, it defaults to \fByes\fP. This option overwrites environment variable \fB$LOCK_BLOCK_DEVICE\fP. The default is not to use any lock at all, but it\(cqs recommended to avoid collisions with \fBsystemd\-udevd\fP(8) or other tools.
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.RE
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.sp
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\fB\-p\fP, \fB\-\-pagesize\fP \fIsize\fP
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.RS 4
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Specify the page \fIsize\fP (in bytes) to use. This option is usually unnecessary; \fBmkswap\fP reads the size from the kernel.
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.RE
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.sp
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\fB\-U\fP, \fB\-\-uuid\fP \fIUUID\fP
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.RS 4
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Specify the \fIUUID\fP to use. The default is to generate a UUID. The format of the UUID is a series of
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hex digits separated by hyphens, like this: "c1b9d5a2\-f162\-11cf\-9ece\-0020afc76f16". The UUID parameter
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may also be one of the following:
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.sp
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\fBclear\fP
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.RS 4
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clear the filesystem UUID
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.RE
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.sp
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\fBrandom\fP
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.RS 4
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generate a new randomly\-generated UUID
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.RE
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.sp
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\fBtime\fP
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.RS 4
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generate a new time\-based UUID
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.RE
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.RE
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.sp
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\fB\-v\fP, \fB\-\-swapversion 1\fP
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.RS 4
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Specify the swap\-space version. (This option is currently pointless, as the old \fB\-v 0\fP option has become obsolete and now only \fB\-v 1\fP is supported. The kernel has not supported v0 swap\-space format since 2.5.22 (June 2002). The new version v1 is supported since 2.1.117 (August 1998).)
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.RE
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.sp
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\fB\-\-verbose\fP
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.RS 4
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Verbose execution. With this option \fBmkswap\fP will output more details about detected problems during swap area set up.
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.RE
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.sp
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\fB\-h\fP, \fB\-\-help\fP
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.RS 4
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Display help text and exit.
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.RE
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.sp
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\fB\-V\fP, \fB\-\-version\fP
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.RS 4
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Print version and exit.
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.RE
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.SH "ENVIRONMENT"
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.sp
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LIBBLKID_DEBUG=all
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.RS 4
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enables libblkid debug output.
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.RE
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.sp
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LOCK_BLOCK_DEVICE=<mode>
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.RS 4
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use exclusive BSD lock. The mode is "1" or "0". See \fB\-\-lock\fP for more details.
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.RE
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.SH "NOTES"
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.sp
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The maximum useful size of a swap area depends on the architecture and the kernel version.
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.sp
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The maximum number of the pages that is possible to address by swap area header is 4294967295 (32\-bit unsigned int). The remaining space on the swap device is ignored.
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.sp
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Presently, Linux allows 32 swap areas. The areas in use can be seen in the file \fI/proc/swaps\fP.
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.sp
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\fBmkswap\fP refuses areas smaller than 10 pages.
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.sp
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If you don\(cqt know the page size that your machine uses, you can look it up with \fBgetconf PAGESIZE\fP.
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.sp
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To set up a swap file, it is necessary to create that file before initializing it with \fBmkswap\fP, e.g. using a command like
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.sp
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.if n .RS 4
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.nf
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.fam C
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# dd if=/dev/zero of=swapfile bs=1MiB count=$((8*1024))
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.fam
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.fi
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.if n .RE
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.sp
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to create 8GiB swapfile.
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.sp
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Please read notes from \fBswapon\fP(8) about \fBthe swap file use restrictions\fP (holes, preallocation and copy\-on\-write issues).
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.SH "SEE ALSO"
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.sp
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\fBfdisk\fP(8),
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\fBswapon\fP(8)
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.SH "REPORTING BUGS"
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.sp
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For bug reports, use the issue tracker at \c
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.URL "https://github.com/util\-linux/util\-linux/issues" "" "."
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.SH "AVAILABILITY"
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.sp
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The \fBmkswap\fP command is part of the util\-linux package which can be downloaded from \c
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.URL "https://www.kernel.org/pub/linux/utils/util\-linux/" "Linux Kernel Archive" "." |