Swap space is a dedicated area on your hard drive that serves as virtual memory. It allows your system to temporarily store data that is not actively used in RAM, helping to improve performance and prevent out-of-memory errors. This guide will walk you through creating a swap partition on CentOS/AlmaLinux.
Step 1: Check Existing Swap Space
Before creating a new swap partition, check if any swap space is already configured:
free -m
If the value under ‘Swap:’ is zero, there is no swap space created:
| Category | Total | Used | Free | Shared | Buff/Cache | Available |
|---|---|---|---|---|---|---|
| Mem | 7820 | 112 | 7643 | 8 | 65 | 7537 |
| Swap | 0 | 0 | 0 | — | — | — |
If any swap space is shown, you can resize it or create an additional swap partition if needed.
Step 2: Create a Swap File
Create a 2GB swap file (adjust size as needed):
sudo dd if=/dev/zero of=/swap count=2048 bs=1MiB
Set the correct permissions to restrict access:
sudo chmod 600 /swap
Step 3: Format the Swap File
Format the swap file to make it usable:
sudo mkswap /swap
Step 4: Activate the Swap File
Enable the swap partition:
sudo swapon /swap
Verify that the swap partition is active:
free -m
Step 5: Make the Swap File Permanent
To ensure the swap file is mounted automatically after each reboot, add it to fstab:
sudo echo "/swap swap swap sw 0 0" >> /etc/fstab
Reboot the system:
sudo reboot
Step 6: Verify the Swap Partition
After rebooting, check that the swap partition is active:
free -h
The output should display the available swap space.
By following these steps, you should have successfully created a swap partition on CentOS/AlmaLinux. Adjust the partition size and settings as needed based on your system’s requirements.