How to Add Swap on CentOS 8

When it comes to optimizing server performance, managing your system’s memory efficiently is key. One of the effective ways to do this on a CentOS 8 system is by adding swap space. Swap can help prevent your system from running out of memory by providing a fallback when your RAM is fully utilized. In this blog post, we will guide you through the process of adding swap on CentOS 8.

What is Swap?

Swap is a space on a hard disk that is used when the amount of physical RAM is full. When your system runs out of RAM, inactive pages in memory are moved to the swap space to free up RAM for active processes. While swap is slower than RAM, it can be crucial for maintaining system stability during peak usage.

Why Use Swap?

• Memory Management: Prevents programs from crashing and helps in efficient memory management.
• System Stability: Reduces the risk of out-of-memory errors, ensuring your applications run smoothly.
• Performance Improvement: Can improve system performance under heavy loads by offloading inactive processes.

Steps to Add Swap on CentOS 8

Step 1: Check Existing Swap Space

Before adding swap, check to see if your system already has swap space configured. You can do this by running the following command in the terminal:

sudo swapon --show

If no output is returned, it means that there’s currently no swap space enabled.

Step 2: Create a Swap File

If you need to add swap, the first thing to do is to create a swap file. You can create a swap file of a specific size using the dd command. For example, to create a 1 GB swap file, you would run:

sudo dd if=/dev/zero of=/swapfile bs=1G count=1

This command creates a file named swapfile in the root directory with a size of 1 GB. You can adjust the count to change the size according to your needs.

Step 3: Set the Right Permissions

For security reasons, it’s important that the swap file is only accessible by the root user. Modify the permissions of the swap file with the following command:

sudo chmod 600 /swapfile

Step 4: Format the Swap File

Now that the swap file is created and secured, you need to format it as swap:

sudo mkswap /swapfile

Step 5: Enable the Swap File

To enable the swap file you just created, use the following command:

sudo swapon /swapfile

After running this command, your swap is active. You can verify it again using:

sudo swapon --show

Step 6: Make Swap Permanent

To ensure that the swap file is mounted automatically at boot time, you’ll need to add it to the /etc/fstab file. Open the file with your preferred text editor:

sudo nano /etc/fstab

Add the following line at the end of the file:

/swapfile swap swap defaults 0 0

Save and exit the file (in Nano, you can do this by pressing CTRL + X, then Y, and Enter).

Step 7: Adjust Swappiness (Optional)

Swappiness is a kernel parameter that defines how aggressively your system will utilize swap space. Its value ranges from 0 to 100, where lower values cause the system to prefer RAM over swap, while higher values will use swap more often.

You can check the current swappiness value with:

cat /proc/sys/vm/swappiness

To change the swappiness value (for example, to 10), run:

sudo sysctl vm.swappiness=10

To make this change permanent, add the following line to /etc/sysctl.conf:

vm.swappiness = 10

Conclusion

Adding swap space on your CentOS 8 server is a straightforward process that can significantly enhance system performance and stability under load. By following these steps, you can ensure that your applications run smoothly, even during peak usage times.

Remember, while swap can be beneficial, it’s no substitute for physical RAM. Always monitor your system’s memory usage and consider scaling your hardware resources when necessary.

If you have further questions or comments about managing swap space on CentOS 8, feel free to share them below!

Happy hosting! 🚀