How to add swap space in centos

Add system swap space for virtual memory paging:

Swap space may be a swap partition, a swap file or a combination of the two. One should size swap space to be at least twice the size of the computer's RAM. (but less than 2GB)

   dd if=/dev/zero of=/swapfile bs=1024 count=265032 - Create file filled with zeros of size 256Mb

   mkswap /swapfile         - Create swap file

   swapon /swapfile         - Begin use of given swap file. Assign a priority with the "-p" flag.

   swapon -s                - List swap files

   cat /proc/swaps          - Same as above

   

This example refers to a swap file. One may also use a swap partition. Make entry to /etc/fstab to permanently use swap file or partition.

/swapfile               swap                    swap    defaults        0 0

Note: To remove the use of swap space, use the command swapoff. If using a swap partition, the partition must be unmounted.