Swap in Linux is a space on a disk drive (HDD or SSD) that is used when the amount of physical memory (RAM) tends to get full.
Swap space is usually created as a dedicated swap partition during the system’s installation but it also can take the form of a swap file.
As usually there is no swap partitions on Linux VMs, the only way to create or extend a swap space there is by creating a swap file.
In this note i will show how to create a swap file on Ubuntu, though these commands should work for the other Linux systems as well.
Cool Tip: How to change swappiness (swap usage tendancy)! Read more →
Create Swap File
Display the current swap usage and list all swap devices and files:
$ free -h $ cat /proc/swaps
Create a swap file with the secure permissions:
$ sudo install -o root -g root -m 0600 /dev/null /swapfile
Use one of the commands below to set the swap file size to 1GB:
$ sudo fallocate -l 1G /swapfile - or - $ dd if=/dev/zero of=/swapfile bs=1k count=1024k
Set up a Linux swap area in the /swapfile:
$ sudo mkswap /swapfile
Add the /swapfile to the system’s swap space:
$ sudo swapon /swapfile
Add the /swapfile swap swap defaults 0 0 to the end of /etc/fstab to make the change permanent:
$ sudo echo "/swapfile swap swap defaults 0 0" | sudo tee -a /etc/fstab
Verify that the system’s swap space has successfully been extended:
$ free -h $ cat /proc/swaps
Cool Tip: How to disable swap in Linux! Read more →