EC2 instances don’t come with swap space configured. On small instances (t2.micro, t3.small), this means your applications can get killed by the Linux OOM (out-of-memory) killer when RAM runs out. Adding swap gives the system overflow space on disk so it can handle temporary memory spikes instead of crashing. This guide shows you how to add swap space on EC2 Ubuntu 22.04.
Prerequisites
- An EC2 instance running Ubuntu 22.04 — follow How to deploy EC2 Ubuntu 22.04 LTS on AWS if you need one
- SSH access to the instance
How Much Swap Do You Need?
| Instance RAM | Recommended Swap |
|---|---|
| 512 MB – 1 GB | 1 GB – 2 GB |
| 2 GB | 2 GB |
| 4 GB | 2 GB – 4 GB |
| 8 GB+ | 2 GB – 4 GB (swap is rarely needed) |
For most EC2 workloads, 1–2 GB of swap is enough. Swap on EBS-backed storage is much slower than RAM, so it’s meant as a safety net — not a replacement for adequate memory. If your instance is consistently using swap, upgrade to a larger instance type instead.
Step 1: Check for Existing Swap
Verify that no swap is currently configured:
sudo swapon --showIf the command returns no output, there’s no swap configured. You can also check with free -h — the Swap row will show all zeros.
Step 2: Create the Swap File
Create a 2 GB swap file:
sudo fallocate -l 2G /swapfileChange 2G to whatever size you need (1G, 4G, etc.).
Set the correct permissions so only root can read and write the file:
sudo chmod 600 /swapfileStep 3: Enable the Swap File
Format the file as swap space and turn it on:
sudo mkswap /swapfile
sudo swapon /swapfileVerify it’s active:
sudo swapon --showYou should see output like:
NAME TYPE SIZE USED PRIO
/swapfile file 2G 0B -2Step 4: Make Swap Persistent Across Reboots
The swap is active now, but it won’t survive a reboot unless you add it to /etc/fstab:
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstabVerify the entry was added:
sudo cat /etc/fstabYou should see a line with /swapfile none swap sw 0 0 at the end.
Step 5: Adjust Swappiness
Swappiness controls how aggressively the kernel moves data from RAM to swap. The default value is 60, but for a server you typically want a lower value so the system prefers RAM and only uses swap when necessary.
Check the current value:
cat /proc/sys/vm/swappinessSet it to 10 (takes effect immediately):
sudo sysctl vm.swappiness=10Make it persistent across reboots:
echo 'vm.swappiness=10' | sudo tee -a /etc/sysctl.conf| Value | Behavior |
|---|---|
| 0 | Only swap to avoid out-of-memory |
| 10 | Swap when RAM is mostly full (recommended for servers) |
| 60 | Default — swaps more aggressively |
| 100 | Swap as much as possible |
Verify Everything
Run free -h to confirm swap is active and the correct size:
free -h total used free shared buff/cache available
Mem: 976Mi 512Mi 112Mi 1Mi 351Mi 312Mi
Swap: 2.0Gi 0B 2.0GiRemoving Swap (If Needed)
To remove the swap file and free up disk space:
sudo swapoff /swapfile
sudo rm /swapfileThen remove the /swapfile none swap sw 0 0 line from /etc/fstab:
sudo nano /etc/fstabDelete the swap line, save, and exit.
Conclusion
Adding swap on EC2 takes a few commands: create the file, format it, enable it, add it to /etc/fstab, and set swappiness to 10. This prevents OOM crashes on small instances without requiring an instance upgrade.
If you’re running database workloads on your instance, swap is especially useful — see How to Install MySQL Database on EC2 Ubuntu 22.04 LTS. To monitor memory and swap usage over time, check out How to Install Datadog Agent with Apache2 on EC2 Ubuntu 22.04.
