How to add swap space in linux

http://www.thegeekstuff.com/2010/08/how-to-add-swap-space/

 

dd if=/dev/zero of=/extraswap bs=1M count=512
mkswap /extraswap
cp /etc/fstab /etc/fstab.mybackup
Add this line at the end of the file
/extraswap   none   swap   sw   0   0
or
swapon /extraswap

Verify whether the newly created swap area is available for your use.
swapon -s