How to Add Swap on Linux

Check Current Swap Status

free -h
sudo swapon --show

Create and Configure Swap File

1. Create the swap file

# Create a 4GB swap file (adjust size as needed)
sudo fallocate -l 4G /swapfile

# Alternative method if fallocate isn't available
# sudo dd if=/dev/zero of=/swapfile bs=1024 count=4194304

2. Set proper permissions and format

sudo chmod 600 /swapfile
sudo mkswap /swapfile

3. Enable swap

sudo swapon /swapfile

4. Make it permanent

Add to /etc/fstab so it mounts on boot:

echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

5. Verify it’s working

free -h
sudo swapon --show

Optimize Swap Settings

Set swappiness (optional)

The vm.swappiness parameter controls how aggressively the Linux kernel uses swap space:

• 0-10: Minimal swapping - keeps data in RAM as long as possible (ideal for servers)
• 60: Default on most systems - balanced approach
• 100: Very aggressive swapping - moves data to swap readily

# For servers (conservative - avoid swap unless necessary)
echo 'vm.swappiness=5' | sudo tee -a /etc/sysctl.conf

# For desktops with limited RAM
echo 'vm.swappiness=10' | sudo tee -a /etc/sysctl.conf

Lower values prioritize keeping data in faster RAM, while higher values free up RAM more aggressively by moving data to slower disk-based swap.

How Much Swap Do You Need?

Server considerations:

• Database servers: Minimal swap (2-4GB)
• Web servers: 1-2GB usually sufficient
• High-memory servers: 0.5-1x RAM or fixed amount

Remove Swap (if needed)

sudo swapoff /swapfile
sudo rm /swapfile
# Remove the line from /etc/fstab

That’s it! Your system now has additional virtual memory to handle memory spikes and prevent out-of-memory crashes.