util-linux-ng-2.17.2/disk-utils/mkswap.8 - nest-learning-thermostat/5.1/util-linux-ng - Git at Google

 .\" Copyright 1998 Andries E. Brouwer (aeb@cwi.nl)
 .\"
 .\" May be distributed under the GNU General Public License
 .\" Rewritten for 2.1.117, aeb, 981010.
 .\"
 .TH MKSWAP 8 "13 March 2009" "Linux" "Linux Programmer's Manual"
 .SH NAME
 mkswap \- set up a Linux swap area
 .SH SYNOPSIS
 .B mkswap
 .RB [ \-c ]
 .RB [ \-f ]
 .RB [ \-p
 .IR PSZ ]
 .RB [ \-L
 .IR label ]
 .RB [ \-U
 .IR uuid ]
 .I device
 .RI [ size ]
 .SH DESCRIPTION
 .B mkswap
 sets up a Linux swap area on a device or in a file.

 The
 .I device
 argument will usually be a disk partition (something like
 .IR /dev/sdb7 )
 but can also be a file.
 The Linux kernel does not look at partition Id's, 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)

 The
 .I size
 parameter is superfluous but retained for backwards compatibility.
 (It specifies the desired size of the swap area in 1024-byte blocks.
 .B mkswap
 will use the entire partition or file if it is omitted.
 Specifying it is unwise - a typo may destroy your disk.)

 The
 .I PSZ
 parameter specifies the page size to use. It is almost always
 unnecessary (even unwise) to specify it, but certain old libc
 versions lie about the page size, so it is possible that
 .B mkswap
 gets it wrong. The symptom is that a subsequent
 .B swapon
 fails because no swap signature is found. Typical values for
 .I PSZ
 are 4096 or 8192.

 After creating the swap area, you need the
 .B swapon
 command to start using it. Usually swap areas are listed in
 .I /etc/fstab
 so that they can be taken into use at boot time by a
 .B swapon -a
 command in some boot script.

 .SH WARNING
 The swap header does not touch the first block. A boot loader or disk label
 can be there, but it is not recommended setup. The recommended setup is to
 use a separate partition for a Linux swap area.

 .B mkswap like many others mkfs-like utils erases the first block to remove
 .B old on-disk filesystems.

 .B mkswap
 refuses to erase the first block on a device with a disk
 label (SUN, BSD, ...) or on whole disk (e.g. /dev/sda).

 .SH OPTIONS
 .TP
 .B \-c
 Check the device (if it is a block device) for bad blocks
 before creating the swap area.
 If any are found, the count is printed.
 .TP
 .B \-f
 Force - 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.

 Without this option
 .B mkswap
 will refuse to erase the first block on a device with a partition table or on
 whole disk (e.g. /dec/sda).
 .TP
 .BI \-p \ PSZ
 Specify the page size to use.
 .TP
 .BI \-L \ label
 Specify a label, to allow swapon by label.
 (Only for new style swap areas.)
 .TP
 .BR \-v0 , \ \-v1
 Specify the swap space version. This option is deprecated and \-v1 is
 supported only.

 The kernel has not supported v0 swap space format since 2.5.22. The new version
 v1 is supported since 2.1.117.

 .TP
 .BI \-U \ uuid
 Specify the uuid to use. The default is to generate UUIDs.

 .SH NOTES
 The maximum useful size of a swap area depends on the architecture and
 the kernel version.
 It is roughly 2GiB on i386, PPC, m68k, ARM, 1GiB on sparc, 512MiB on mips,
 128GiB on alpha and 3TiB on sparc64. For kernels after 2.3.3 there is no
 such limitation.

 Note that before 2.1.117 the kernel allocated one byte for each page,
 while it now allocates two bytes, so that taking a swap area of 2 GiB
 in use might require 2 MiB of kernel memory.

 Presently, Linux allows 32 swap areas (this was 8 before Linux 2.4.10).
 The areas in use can be seen in the file
 .I /proc/swaps
 (since 2.1.25).

 .B mkswap
 refuses areas smaller than 10 pages.

 If you don't know the page size that your machine uses, you may be
 able to look it up with "cat /proc/cpuinfo" (or you may not -
 the contents of this file depend on architecture and kernel version).

 To setup a swap file, it is necessary to create that file before
 initializing it with
 .BR mkswap ,
 e.g. using a command like

 .nf
 .RS
 # dd if=/dev/zero of=swapfile bs=1024 count=65536
 .RE
 .fi

 Note that a swap file must not contain any holes (so, using
 .BR cp (1)
 to create the file is not acceptable).


 .SH "SEE ALSO"
 .BR fdisk (8),
 .BR swapon (8)
 .SH AVAILABILITY
 The mkswap command is part of the util-linux-ng package and is available from
 ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
	.\" Copyright 1998 Andries E. Brouwer (aeb@cwi.nl)
	.\"
	.\" May be distributed under the GNU General Public License
	.\" Rewritten for 2.1.117, aeb, 981010.
	.\"
	.TH MKSWAP 8 "13 March 2009" "Linux" "Linux Programmer's Manual"
	.SH NAME
	mkswap \- set up a Linux swap area
	.SH SYNOPSIS
	.B mkswap
	.RB [ \-c ]
	.RB [ \-f ]
	.RB [ \-p
	.IR PSZ ]
	.RB [ \-L
	.IR label ]
	.RB [ \-U
	.IR uuid ]
	.I device
	.RI [ size ]
	.SH DESCRIPTION
	.B mkswap
	sets up a Linux swap area on a device or in a file.

	The
	.I device
	argument will usually be a disk partition (something like
	.IR /dev/sdb7 )
	but can also be a file.
	The Linux kernel does not look at partition Id's, 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)

	The
	.I size
	parameter is superfluous but retained for backwards compatibility.
	(It specifies the desired size of the swap area in 1024-byte blocks.
	.B mkswap
	will use the entire partition or file if it is omitted.
	Specifying it is unwise - a typo may destroy your disk.)

	The
	.I PSZ
	parameter specifies the page size to use. It is almost always
	unnecessary (even unwise) to specify it, but certain old libc
	versions lie about the page size, so it is possible that
	.B mkswap
	gets it wrong. The symptom is that a subsequent
	.B swapon
	fails because no swap signature is found. Typical values for
	.I PSZ
	are 4096 or 8192.

	After creating the swap area, you need the
	.B swapon
	command to start using it. Usually swap areas are listed in
	.I /etc/fstab
	so that they can be taken into use at boot time by a
	.B swapon -a
	command in some boot script.

	.SH WARNING
	The swap header does not touch the first block. A boot loader or disk label
	can be there, but it is not recommended setup. The recommended setup is to
	use a separate partition for a Linux swap area.

	.B mkswap like many others mkfs-like utils erases the first block to remove
	.B old on-disk filesystems.

	.B mkswap
	refuses to erase the first block on a device with a disk
	label (SUN, BSD, ...) or on whole disk (e.g. /dev/sda).

	.SH OPTIONS
	.TP
	.B \-c
	Check the device (if it is a block device) for bad blocks
	before creating the swap area.
	If any are found, the count is printed.
	.TP
	.B \-f
	Force - 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.

	Without this option
	.B mkswap
	will refuse to erase the first block on a device with a partition table or on
	whole disk (e.g. /dec/sda).
	.TP
	.BI \-p \ PSZ
	Specify the page size to use.
	.TP
	.BI \-L \ label
	Specify a label, to allow swapon by label.
	(Only for new style swap areas.)
	.TP
	.BR \-v0 , \ \-v1
	Specify the swap space version. This option is deprecated and \-v1 is
	supported only.

	The kernel has not supported v0 swap space format since 2.5.22. The new version
	v1 is supported since 2.1.117.

	.TP
	.BI \-U \ uuid
	Specify the uuid to use. The default is to generate UUIDs.

	.SH NOTES
	The maximum useful size of a swap area depends on the architecture and
	the kernel version.
	It is roughly 2GiB on i386, PPC, m68k, ARM, 1GiB on sparc, 512MiB on mips,
	128GiB on alpha and 3TiB on sparc64. For kernels after 2.3.3 there is no
	such limitation.

	Note that before 2.1.117 the kernel allocated one byte for each page,
	while it now allocates two bytes, so that taking a swap area of 2 GiB
	in use might require 2 MiB of kernel memory.

	Presently, Linux allows 32 swap areas (this was 8 before Linux 2.4.10).
	The areas in use can be seen in the file
	.I /proc/swaps
	(since 2.1.25).

	.B mkswap
	refuses areas smaller than 10 pages.

	If you don't know the page size that your machine uses, you may be
	able to look it up with "cat /proc/cpuinfo" (or you may not -
	the contents of this file depend on architecture and kernel version).

	To setup a swap file, it is necessary to create that file before
	initializing it with
	.BR mkswap ,
	e.g. using a command like

	.nf
	.RS
	# dd if=/dev/zero of=swapfile bs=1024 count=65536
	.RE
	.fi

	Note that a swap file must not contain any holes (so, using
	.BR cp (1)
	to create the file is not acceptable).


	.SH "SEE ALSO"
	.BR fdisk (8),
	.BR swapon (8)
	.SH AVAILABILITY
	The mkswap command is part of the util-linux-ng package and is available from
	ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.