Autres langues

Langue: en

Version: 25 September 1995 (fedora - 01/12/10)

Autres sections - même nom

Section: 8 (Commandes administrateur)


swapon, swapoff - enable/disable devices and files for paging and swapping


Get info:
swapon -s [-h] [-V]

swapon [-f] [-p priority] [-v] specialfile...
swapoff [-v] specialfile...

Enable/disable all:
swapon -a [-e] [-f] [-v]
swapoff -a [-v]


swapon is used to specify devices on which paging and swapping are to take place.

The device or file used is given by the specialfile parameter. It may be of the form -L label or -U uuid to indicate a device by label or uuid.

Calls to swapon normally occur in the system boot scripts making all swap devices available, so that the paging and swapping activity is interleaved across several devices and files.

swapoff disables swapping on the specified devices and files. When the -a flag is given, swapping is disabled on all known swap devices and files (as found in /proc/swaps or /etc/fstab).

-a, --all
All devices marked as ``swap'' in /etc/fstab are made available, except for those with the ``noauto'' option. Devices that are already being used as swap are silently skipped.
-e, --ifexists
Silently skip devices that do not exist.
-f, --fixpgsz
Reinitialize (exec /sbin/mkswap) the swap space if its page size does not match that of the the current running kernel. mkswap(2) initializes the whole device and does not check for bad blocks.
-h, --help
Provide help.
-L label
Use the partition that has the specified label. (For this, access to /proc/partitions is needed.)
-p, --priority priority
Specify the priority of the swap device. priority is a value between 0 and 32767. Higher numbers indicate higher priority. See swapon(2) for a full description of swap priorities. Add pri=value to the option field of /etc/fstab for use with swapon -a.
-s, --summary
Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25.
-U uuid
Use the partition that has the specified uuid.
-v, --verbose
Be verbose.
-V, --version
Display version.


You should not use swapon on a file with holes. Swap over NFS may not work.

swapon automatically detects and rewrites swap space signature with old software suspend data (e.g S1SUSPEND, S2SUSPEND, ...). The problem is that if we don't do it, then we get data corruption the next time an attempt at unsuspending is made.


swapon(2), swapoff(2), fstab(5), init(8), mkswap(8), rc(8), mount(8)


/dev/sd?? standard paging devices
/etc/fstab ascii filesystem description table


The swapon command appeared in 4.0BSD.


The swapon command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.