Learn the Linux Command - swapon

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


/sbin/swapon [-h -V] 
/sbin/swapon -a [-v] [-e] 
/sbin/swapon [-v] [-p priorityspecialfile ... 
/sbin/swapon [-s] 
/sbin/swapoff [-h -V] 
/sbin/swapoff -a 
/sbin/swapoff specialfile ...  


Swapon is used to specify devices on which paging and swapping are to take place. Calls to swapon normally occur in the system multi-user initialization file /etc/rc making all swap devices available, so that the paging and swapping activity is interleaved across several devices and files.

Normally, the first form is used:


Provide help


Display version


Display swap usage summary by device. Equivalent to "cat /proc/swaps". Not available before Linux 2.1.25.


All devices marked as ``swap'' swap devices in /etc/fstab are made available. Devices that are already running as swap are silently skipped.


When -a is used with swapon, -e makes swapon silently skip devices that do not exist.

-p priority

Specify priority for swapon. This option is only available if swapon was compiled under and is used under a 1.3.2 or later kernel. priority is a value between 0 and 32767. 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.

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). 


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