Creating a swap file on Ubuntu 18.04 LTS

When using a low-cost Amazon Lightsail plan, RAM can sometimes be insufficient. Upgrading the instance plan is the best solution, but I allocated swap space instead.

Check the system’s swap space

Check whether the system already has swap space.

$ sudo swapon --show

If nothing is printed, there is no swap space.

Create the swap file

Create a swap file in the root directory.
(1024 bytes * 1,048,576 blocks = 1 GB)

$ sudo dd if=/dev/zero of=/swapfile bs=1024 count=1048576

Change the permissions of /swapfile.

$ sudo chmod 600 /swapfile

Mark the created file as swap space.

$ sudo mkswap /swapfile

Enable the swap file

Make the system use the swap file.

$ sudo swapon /swapfile

Check the swap space information.

$ free -h

Result

Mount at system boot

Configure the system to mount the swap file automatically on boot.
Add /swapfile swap swap defaults 0 0 to the last line of /etc/fstab.

$ sudo echo '/swapfile swap swap defaults 0 0' | sudo tee -a /etc/fstab

Extra: Lightsail instance launch script

This automates the steps above.

On the instance creation page, select “Add launch script”.

Enter the following as the launch script:

dd if=/dev/zero of=/swapfile bs=1024 count=1048576
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
echo '/swapfile swap swap defaults 0 0' | tee -a /etc/fstab

Commands sent during server provisioning run as root, so sudo is not necessary.

Then finish the remaining settings and create the instance.