How to Extend Swap Space using Swap file in Linux

There are some scenarios where our Linux box is running out of swap space so in that case we can extend the swap space using swap partition but due to unavailability of free partitions on the disk, we are unable to extend it.

So in such cases we can extend or increase swap space using a swap file

Below are the Steps to extend Swap Space using Swap File in Linux

Lets first check the size of existing swap space / partition using the command like ‘free -m‘ and ‘swapon -s


In my case size of swap partition is 2 GB. So we will be extending swap space by 1 GB.

Step:1 Create a swap file of size 1 GB using below dd Command
[[email protected] ~]# dd if=/dev/zero of=/swap_file bs=1G count=1
1+0 records in
1+0 records out
1073741824 bytes (1.1 GB) copied, 414.898 s, 2.6 MB/s
[[email protected] ~]#

Replace the value of ‘bs‘ and ‘count‘ according your requirement.

Step:2 Secure the swap file with permissions 644.
[[email protected] ~]# chmod 600 /swap_file
Step:3 Enable the Swap Area on the file (swap_file)

Use mkswap command to enable swap area

[[email protected] ~]# mkswap /swap_file
Setting up swapspace version 1, size = 1048572 KiB
no label, UUID=f7b3ae59-c09a-4dc2-ba4d-c02abb7db33b
[[email protected] ~]#
Step:4 Add the swap file entry in the fstab file

Add the below entry in the fstab file so that swap file become persistent across every reboot.

/swap_file  swap  swap  defaults  0 0


Step:5 Enable the swap file using ‘mkswap on’ command.
[[email protected] ~]# swapon /swap_file
[[email protected] ~]#
Step:6 Now verify the swap space


Note: To disable the swap file for any troubleshooting point of view, use swapoff command as shown below and to re-enable swap file then use swapon command as shown in step5.

[[email protected] ~]# swapoff /swap_file
[[email protected] ~]#

Please share your valuable inputs and comments on this article.

1 thought on “How to Extend Swap Space using Swap file in Linux”

  1. Use fallocate, not dd, for creating /swap_file . It’s faster and doesn’t require an enormous memory buffer.
    sudo fallocate -l 4G /swap_file

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