Add swap file in CentOS 6.4

Add swap file in CentOS 6.4

Swapon command with option -s, displays the current swap space in KB.

# swapon -s
If a file with the name /extraswap already exists, check it with ‘ls’ command and delete it using ‘rm’ command.
#  ls /extraswap
#  rm -rf /extraswap

The following dd command example creates a swap file with the name “extraswap” under / directory with a size of 1024MB (1GB).

# dd if=/dev/zero of=/extraswap bs=1M count=1024

Change the permission of the swap file so that only root can access it.

# chmod 600 /extraswap

Make this file as a swap file using mkswap command.

# mkswap /extraswap

Enable the newly created swapfile.

# swapon /extraswap

To make this swap file available as a swap area even after the reboot, add the following line to the /etc/fstab file.

/extraswap swap swap defaults 0 0

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

# swapon -s