Thursday 28 February 2013

How to create SWAP space in Linux Servers

You need to use the dd command to create swap file. The mkswap command is used to set up a Linux swap area on a device or in a file.

Login as root user, and use the following command to create a swap file.

The following dd command example creates a swap file with the name “tmpDSK” under /backup directory with a size of 2000MB (2GB)

# dd if=/dev/zero of=/backup/tmpDSK bs=1M count=2000

Setup correct file permission for security reasons, enter:

# chown root:root  /backup/tmpDSK
# chmod 600 /backup/tmpDSK

Make this file as a swap file using mkswap command.

# mkswap /backup/tmpDSK
Setting up swapspace version 1, size = 2097147 kB

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

/backup/tmpDSK       swap                     swap     defaults        0 0

Enable the newly created swapfile.

# swapon /backup/tmpDSK

# free -m
             total       used       free     shared    buffers     cached
Mem:          4050       3222        828          0        210       2589
-/+ buffers/cache:        422       3628
Swap:         1999          0       1999

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