Quick answer: Add swap on a Linux VPS by creating a file with fallocate, setting chmod 600, running mkswap and swapon, then adding it to /etc/fstab so it survives reboot. Lower vm.swappiness to about 10 so swap is used only under memory pressure. Swap prevents crashes but is slower than RAM.
A swap file gives a Linux VPS extra virtual memory on disk, which prevents processes from being killed when RAM runs out. It is a cheap safety net for memory spikes, especially on smaller plans. Here is how to add one safely.
swapon --show free -h
If the output is empty or shows 0 swap, continue. If swap already exists, you usually do not need more.
A common size is equal to your RAM, up to about 4 GB. Create a 2 GB file:
fallocate -l 2G /swapfile chmod 600 /swapfile mkswap /swapfile swapon /swapfile
The chmod 600 is important - the swap file must be readable only by root.
So swap survives a reboot, add it to /etc/fstab:
echo '/swapfile none swap sw 0 0' >> /etc/fstab
Swappiness controls how readily Linux moves data to swap. For a server, a lower value keeps more in fast RAM and uses swap only under pressure:
sysctl vm.swappiness=10 echo 'vm.swappiness=10' >> /etc/sysctl.conf
free -h swapon --show
You should now see the swap space active. Remember that swap is slower than RAM - it prevents crashes but is not a substitute for enough memory. If the server swaps constantly, the real fix is more RAM or lighter workloads.
How much swap should I create?
A common choice is equal to RAM, up to about 4 GB.
Is swap a substitute for more RAM?
No - it prevents out-of-memory crashes but is slower; constant swapping means you need more RAM.
If your applications regularly outgrow their memory, a right-sized plan solves it properly: a SoftSys managed Linux VPS can be scaled to more RAM without rebuilding, and our team will advise on the correct size for your workload.
