[Query] Confusion of the Swap when using 'free -m' command

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LEARN ABOUT REDHAT

swapon

SWAPON(8)						     Linux Programmer's Manual							 SWAPON(8)

NAME

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

SYNOPSIS

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

DESCRIPTION

       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:

       -h     Provide help

       -V     Display version

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

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

       -e     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).

NOTE

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

SEE ALSO

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

FILES

       /dev/hd??  standard paging devices
       /dev/sd??  standard (SCSI) paging devices
       /etc/fstab ascii filesystem description table

HISTORY

       The swapon command appeared in 4.0BSD.

Linux 1.x							 25 September 1995							 SWAPON(8)

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