Your app crashed overnight, the log ends with “Killed”, and dmesg mentions the OOM killer? Your server ran out of memory, and the kernel executed the biggest process to survive — usually MySQL or your application. On small VPS plans, swap space is the cheap insurance against exactly this. Ubuntu cloud images ship with no swap at all by default, so let's fix that in five minutes.
Step 1 — Check whether you already have swap
free -h swapon --show
If the Swap line shows 0B, continue.
Step 2 — Create the swap file
Rule of thumb for servers: swap = RAM for machines up to 2 GB; half the RAM (capped around 4 GB) beyond that.
sudo fallocate -l 2G /swapfile sudo chmod 600 /swapfile sudo mkswap /swapfile sudo swapon /swapfile
The chmod 600 matters — swap can contain fragments of any process's memory, including secrets, so only root may read it.
Step 3 — Verify and make it permanent
free -h swapon --show
Swap is live but would vanish at reboot. Persist it in /etc/fstab:
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
Step 4 — Tune swappiness for a server
vm.swappiness (0–100, default 60) controls how eagerly the kernel swaps. Desktops like 60; on servers you want RAM used for real work and swap kept for emergencies:
sudo sysctl vm.swappiness=10 echo 'vm.swappiness=10' | sudo tee /etc/sysctl.d/99-swappiness.conf
Removing or resizing swap
sudo swapoff /swapfile sudo rm /swapfile # then recreate at the new size # and remove/adjust the /etc/fstab line
Frequently asked questions
Is swap bad for SSDs?
Modern SSD endurance makes occasional swapping a non-issue. A server that is constantly swapping, though, has a memory problem swap cannot solve — check what is eating your RAM and consider upgrading the plan.
My VPS feels slow since adding swap — why?
Swap is orders of magnitude slower than RAM; heavy swap use means the working set no longer fits in memory. Swap prevents crashes; it does not add capacity. If free -h shows swap heavily used day-to-day, it is time for more RAM — our VPS plans scale in minutes.
Related Ubuntu guides
- How to Monitor Ubuntu Server Performance: CPU, RAM and Processes
- How to Check and Free Up Disk Space on Ubuntu Server
- Initial Ubuntu 24.04 Server Setup Guide: Secure Your New VPS in 10 Steps
- How to Install a LEMP Stack (Nginx, MySQL, PHP) on Ubuntu 24.04
Prefer to have experts handle it?
LFA IT provides fully managed Ubuntu VPS and dedicated servers — initial setup, security hardening, monitoring and 24/7 support, so you can focus on your business. Explore our hosting and server management services or open a support ticket and our engineers will take it from there.
