Creating swap space using a file in Linux

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If we don’t have any additional disks, you can create a file somewhere on our filesystem, and use that file for swap space.

The following dd command example creates a swap file with the name “swapfile” under /root directory with a size of 2GB.

# dd if=/dev/zero of=/root/swapfile bs=1M count=2048

list the create file

# ls -l /root/swapfile

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

# chmod 600 /root/swapfile

Make this file as a swap file using mkswap command.

# mkswap /root/swapfile

Enable the newly created swapfile.

# swapon /root/swapfile

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

# vim /etc/fstab
/root/swapfile swap swap defaults 0 0

Verify whether the newly created swap area is available for your use by running the status option.

# swapon -s

To see the Swap free size

# free -k

In the output of swapon -s command, the type column will say “file” if the swap space is created from a swap file.

To disable and enable all swap space use below commands.

# swapoff -a

# swapon -a

We have done with creating a swap space using the file.

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