Swapon

swapon is the command used to show active swap areas, or activate a swap area (file or partition.)

Usage
Enable a swap area swapon [-v] 

Enable all swap areas mentioned in /etc/fstab swapon -a [-v]

Disable a swap area swapoff [-v] 

Show active swap areas swapon -s [-v]

where the target is a swap file or partition

Provided by
Most (all?) Linux distributions incorporate this from the util-linux package