Add Swap on Ubuntu, Debian, AlmaLinux, and Rocky Linux

Why adding swap helps a small VPS

If your VPS is short on RAM, add swap before apps start failing under load. Swap gives the kernel room to move inactive memory pages out of RAM, which helps during package updates, control panel installs, WordPress bursts, and database spikes. It is not a replacement for real memory, but it can keep a low-RAM server running long enough for you to fix the underlying issue.

On Hostperl VPS plans, swap is often the difference between a clean launch and a restart loop after a busy deployment. If you are still sizing the server, review Hostperl VPS options first, then come back and add swap only if the workload genuinely needs it.

This guide shows a safe way to create a swap file on Ubuntu, Debian, AlmaLinux, and Rocky Linux, then verify that it survives reboot. It also covers the checks you should run after the change, so you can tell whether the swap is helping or just masking a capacity problem.

Connect to the server and check the OS

On your local computer

ssh root@203.0.113.10

203.0.113.10 is a reserved documentation example. Replace it with the real public IP assigned to your server. If your provider gives you a default non-root login, use that account in the same way, for example ssh deploy@203.0.113.10.

Keep this first root session open while you work.

On the VPS as root

cat /etc/os-release

This tells you whether you are on Ubuntu, Debian, AlmaLinux, or Rocky Linux. The package and service checks below use that output to point you to the right commands.

Check whether you actually need swap

On the VPS as root

free -h

Look at the Mem: and Swap: lines. If swap is already present, you may only need to resize it or tune swappiness. If swap is zero and RAM usage regularly climbs above 80%, creating a swap file is a reasonable next step.

For a quick view of current pressure, run:

vmstat 1 5

Frequent si and so activity means the system is swapping in and out already. A little is normal during spikes; constant activity means you should treat swap as a short-term cushion, not a final fix.

Add swap on Ubuntu and Debian

On the VPS as root

These commands create a 2 GB swap file at /swapfile. If your VPS is very small, 1 GB is acceptable. For larger VPS plans, 2 GB or 4 GB is more common.

fallocate -l 2G /swapfile

If fallocate fails on your filesystem, use this alternative:

dd if=/dev/zero of=/swapfile bs=1M count=2048 status=progress

Set the correct permissions so only root can read the file:

chmod 600 /swapfile

Format the file as swap and enable it immediately:

mkswap /swapfile
swapon /swapfile

Confirm the kernel accepted it:

swapon --show
free -h

You should now see /swapfile listed and the swap total should be greater than zero.

Make the change permanent by adding it to /etc/fstab:

cp /etc/fstab /etc/fstab.bak
printf '/swapfile none swap sw 0 0\n' >> /etc/fstab

Test the fstab entry without rebooting:

swapoff /swapfile
swapon /swapfile
swapon --show

If swapon --show lists the file again, the line in /etc/fstab is valid.

Add swap on AlmaLinux and Rocky Linux

On the VPS as root

AlmaLinux and Rocky Linux use the same swap file approach. The commands are identical here, which keeps recovery simple across RHEL-compatible systems.

fallocate -l 2G /swapfile

Use dd if fallocate is not supported on your filesystem:

dd if=/dev/zero of=/swapfile bs=1M count=2048 status=progress

Lock down the file, then initialize it:

chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile

Verify the swap is active:

swapon --show
free -h

Persist it across reboots with /etc/fstab:

cp /etc/fstab /etc/fstab.bak
printf '/swapfile none swap sw 0 0\n' >> /etc/fstab

Check the entry by turning swap off and back on:

swapoff /swapfile
swapon /swapfile
swapon --show

If the file appears again, your system will mount swap after reboot too.

Tune how aggressively Linux uses swap

Most VPS hosts do not need an aggressive swap setting. A conservative value keeps RAM usage steady while avoiding unnecessary disk churn. A vm.swappiness value of 10 is a common starting point for web servers and small databases.

On the VPS as root

cat <<'EOF' > /etc/sysctl.d/99-swap.conf
vm.swappiness = 10
EOF
sysctl --system

Then confirm the value took effect:

sysctl vm.swappiness

If you run a database-heavy stack, you may choose a slightly higher value after testing. Do not set it blindly. Watch memory pressure first, especially if the VPS also runs MySQL, PostgreSQL, or a control panel.

For a broader memory strategy, Hostperl’s note on swap sizing on Ubuntu and AlmaLinux pairs well with database sizing decisions when you are planning a new launch.

Make the server safer before leaving the session

Swap helps stability, but low-RAM servers still need basic housekeeping. Update packages, then reboot later only after you have confirmed the new swap survives a reboot test.

Ubuntu and Debian

apt update
apt upgrade -y

AlmaLinux and Rocky Linux

dnf update -y

If you are using a Hostperl VPS for a live site, keep an eye on memory after updates. Package upgrades can temporarily use more RAM than normal. Swap gives you breathing room during that maintenance window.

Verify the result from the server and a client

On the VPS as root

swapon --show
free -h
ls -lh /swapfile
cat /etc/fstab | grep swap

Expected result: /swapfile appears in swapon --show, free -h shows non-zero swap, the file permissions are -rw-------, and the fstab line exists.

Check that the system boots with the entry intact by rebooting only after you have saved your work:

reboot

On your local computer

Reconnect after the reboot and confirm the swap is still active:

ssh root@203.0.113.10

Then run:

swapon --show
free -h

If swap vanished after reboot, the issue is usually a bad /etc/fstab line or a typo in the file path.

Troubleshooting the most likely problems

1) fallocate fails
Diagnostic command:

fallocate -l 2G /swapfile

If it errors out, use the dd fallback shown above. That command works on more filesystems, though it takes longer.

2) Swap is listed but the server still feels slow
Diagnostic command:

vmstat 1 10

If you see constant swapping, the VPS is undersized for the workload. Reduce the app footprint, add RAM, or move to a larger Hostperl VPS. Swap can cushion a burst, but it cannot make a 1 GB machine behave like a 4 GB server.

3) The system refuses to boot after editing /etc/fstab
Diagnostic command after rescue access:

cat /etc/fstab

Remove the bad swap line, save the file, then test with swapon --show again. A single typo or extra character is enough to break boot-time mounting.

4) You want to remove swap later
Run this carefully only if you are sure the server has enough RAM:

swapoff /swapfile
sed -i '\|/swapfile none swap sw 0 0|d' /etc/fstab
rm -f /swapfile

After that, check free -h again to confirm swap is gone.

FAQ

How much swap should I add?
For most small VPS installs, 1 GB to 2 GB is enough. Use more only if you have a clear reason and enough disk space.

Is swap bad for SSDs?
Not by itself. Heavy, constant swapping is the problem. If your server is swapping all day, the VPS is undersized.

Should I use a swap file or a swap partition?
A swap file is easier on VPS hosting and simpler to resize. A partition is fine on bare metal, but it is less flexible for most customers.

Will swap fix out-of-memory crashes?
It can reduce them, but not always. If the workload keeps growing, add RAM or move the service to a larger VPS.

Final check before you call it done

Run one last command set and save the output for your records:

swapon --show
free -h
uptime

If swap is active after reboot and the server remains responsive, the job is done. For customers who need help choosing the right VPS size before they hit this point again, Hostperl’s managed VPS hosting is a better fit than repeatedly stretching a small server past its limits.