How to Add Swap Space on Linux (Ubuntu)

In this tutorial, you'll learn about How to Add Swap Space on Linux (Ubuntu). We cover key concepts, practical examples, and best practices to help you understand and apply this topic effectively.

The Problem

Your server runs out of memory and the OOM killer terminates processes. Swap gives you a safety buffer by using disk space as extra RAM.

Quick Fix

1. Check current swap

free -h

If Swap shows 0B, you have no swap.

2. Create a swap file (1GB example)

sudo fallocate -l 1G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

3. Verify it's active

free -h

Expected output:

              total        used        free      ...
Mem:           1.9G        1.2G        0.7G
Swap:          1.0G        0.0G        1.0G

4. Make permanent

Add to /etc/fstab:

echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

5. Adjust swappiness (optional)

Lower = use RAM more, swap less. For servers: 10. For desktops: 60.

sudo sysctl vm.swappiness=10
echo 'vm.swappiness=10' | sudo tee -a /etc/sysctl.conf

Sizing Guide