How to Configure Swap on Linux
Short answerCreate a swap file (common on VPS disks), set permissions, mark it with mkswap, enable it with swapon, add it to /etc/fstab, then optionally tune vm.swappiness. Swap is emergency overflow — it is slower than RAM.
Overview
Swap helps small VPS plans survive short memory spikes. It does not replace upgrading RAM if you are constantly swapping. VPSGrid Linux VPS plans are unmanaged — you configure swap inside the guest.
When swap helps
- Occasional spikes (builds, apt/dnf, bursts of traffic)
- Preventing the OOM killer from immediately killing processes on low-RAM plans
If the disk is thrashing continuously, upgrade the plan instead of adding huge swap.
1) Check current memory and swap
free -h
swapon --show
df -h /Confirm you have enough free disk for the swap file you want (example below uses 2G).
2) Create a 2G swap file
Run as root (or with sudo). Adjust size if needed:
fallocate -l 2G /swapfile || dd if=/dev/zero of=/swapfile bs=1M count=2048
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
swapon --show
free -hIf fallocate fails on some filesystems, the dd fallback above still works. Never make /swapfile world-readable.
3) Make swap permanent
Add to /etc/fstab (one line):
echo '/swapfile none swap sw 0 0' | tee -a /etc/fstab
# verify
tail -n 3 /etc/fstab
# safe test without reboot
swapoff /swapfile && swapon -a && swapon --show4) Optional: swappiness
Lower values prefer RAM longer before swapping (common on servers):
# temporary
sysctl vm.swappiness=10
# permanent
echo 'vm.swappiness=10' | tee /etc/sysctl.d/99-swappiness.conf
sysctl --system | grep swappiness5) Remove swap later (if needed)
swapoff /swapfile
# remove the /swapfile line from /etc/fstab
rm /swapfileFrequently Asked Questions
How big should swap be?
For many small VPS workloads, 1–2× RAM is a common starting point, capped by free disk. Prefer upgrading RAM if swap is busy all the time.
Swap partition vs swap file?
A swap file is usually easier on VPS images without a dedicated swap partition. Performance difference is typically small for this use case.
Will swap speed up my site?
No. Swap prevents crashes under pressure; active use of swap is slower than RAM. Optimize the app or upgrade the plan for sustained load.
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Need More Help?
Open a ticket at billing.vpsgrid.net with your service ID, free -h output, and the exact error from mkswap/swapon.
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