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How to add swap on Ubuntu

Swap is disk space used as virtual memory when RAM starts to run low. It is not as fast as real memory, but it can help you:

  • avoid sudden process kills during memory pressure

  • improve stability on smaller VPS plans

  • absorb short usage spikes

When it makes sense

Swap is especially useful on VPS plans with limited memory, such as 1โ€“2 GB RAM. That said, if your workload constantly needs more RAM than the server has, swap is not a real substitute for upgrading.

1. Check current memory and swap

free -h
swapon --show

If swapon --show returns nothing, no active swap is configured.

2. Create a swap file

Example for a 2 GB swap file:

sudo fallocate -l 2G /swapfile

If fallocate does not work in your environment, use:

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

3. Set secure permissions

4. Format the file as swap

5. Enable swap

Verify it:

6. Make it persistent after reboot

Edit /etc/fstab:

Add this line at the end:

7. Optional: tune swappiness

The swappiness value controls how aggressively Linux uses swap. Check the current value:

For many VPS servers, a value like 10 or 20 is reasonable.

Apply it temporarily:

Make it persistent:

Choosing a swap size

There is no perfect rule, but a practical guideline is:

  • 1 GB RAM โ†’ 1โ€“2 GB swap

  • 2 GB RAM โ†’ 2 GB swap

  • 4 GB RAM or more โ†’ 1โ€“2 GB swap as a small buffer if needed

Best practices

  • Do not treat swap as the main fix for not having enough RAM.

  • Monitor actual usage with htop, free -h, or vmstat.

  • If the server swaps heavily all the time, performance can drop sharply.

How to remove swap

If you want to disable it later:

Then remove the corresponding line from /etc/fstab.

Conclusion

A properly configured swap file can make a small VPS more stable, especially during brief memory spikes.

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