How to Create a 4 GB SWAP File on Rocky Linux 9 VM with 2 vCPU and 8 GB Memory

What is a Linux Swap File?

First, let's delve into the concept of a Linux swap file.

A swap file in Linux is a space on a hard drive or SSD that is used as virtual memory. When your system's RAM is full, the operating system can "swap" inactive pages (chunks of memory) from RAM to this space on the disk. This process effectively increases the amount of available memory, allowing more applications to run concurrently.

Why is it Important?

1. Enhanced Performance: By offloading inactive pages from RAM, swap files enable systems to keep functioning smoothly, even when running memory-intensive applications.
2. Memory Management: It helps in managing memory more effectively, making better use of the system's physical memory and hard drive space.
3. Avoiding Out-of-Memory Crashes: If all physical RAM is used up, a swap file can prevent a system from crashing by providing additional virtual memory space.

When to Use a Swap File?

1. Low RAM: If your system has limited physical memory (RAM), implementing a swap file can alleviate potential memory issues.
2. Running Memory-Intensive Applications: If you run applications that use a significant amount of memory, having a swap file can help ensure that they run smoothly.
3. Hibernate Functionality: Hibernate feature in Linux requires swap space to save the current state of all active applications and documents.

When Not to Use a Swap File?

1. High-Performance Systems with Sufficient RAM: If you have a system with ample physical RAM and are not running memory-hogging applications, a swap file might be unnecessary.
2. SSD Concerns: Continuous reading and writing to an SSD due to swapping can lead to wear and tear of the SSD over time. This is less of a concern with modern SSDs, but it's something to consider.
3. Latency-Sensitive Applications: Swap space is slower than RAM, so if you're running applications that require ultra-fast access to memory, relying on a swap file might degrade performance.

Tips to keep in mind when creating a swap file:

• The size of the swap file should be at least equal to the amount of RAM on your system.
• You can create a swap file on any available disk partition. However, it is best to create it on a separate partition from your root partition. This will help to protect your data in the event of a system crash.
• You can also create a swap file on a USB drive or other removable media. This is a good option if you need to add swap space to a system that does not have enough free disk space on the internal hard drive.

Creating a 4 GB SWAP File on Rocky Linux 9 VM with 2 vCPU and 8 GB Memory

Please remember to adjust the SWAP size according to your specific requirements and workload. Having a SWAP space around half the size of your physical RAM is often considered a good practice, but it may vary depending on the application and system usage.

Step 1: Check Existing SWAP

Before creating a new SWAP file, check if there is already a SWAP file or partition in place:

sudo swapon --show

Step 2: Create a SWAP File

If there's no existing SWAP, you can create a 4 GB SWAP file using the following commands:

sudo dd if=/dev/zero of=/swapfile bs=1G count=4 status=progress

Step 3: Set Permissions

It's essential to set the correct permissions to secure the SWAP file:

sudo chmod 600 /swapfile

Step 4: Format the SWAP File

Format the file to be used as SWAP:

sudo mkswap /swapfile

Step 5: Enable the SWAP File

Activate the SWAP file:

sudo swapon /swapfile

Step 6: Make the SWAP File Permanent

To make the SWAP file permanent across reboots, add the following entry to the /etc/fstab file:

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

Step 7: Verify the SWAP Space

Finally, verify that the SWAP file is enabled and working correctly:

sudo swapon --show
free -h

And that's it!

Your Rocky Linux 9 VM now has an additional 4 GB of SWAP space to supplement its 8 GB of physical RAM.

Creating a swapfile for a system with 8 GB of RAM using fallocate

1. Become a superuser (root) by typing:

   sudo su

2. Create a swap file with the following command:

   fallocate -l 8G /swapfile

   This will create a swap file of 8 GB in size in the / directory.

3. Change the permissions of the swap file so that only root can access it:

   chmod 600 /swapfile

4. Initialize the swap file as a swap partition:

   mkswap /swapfile

5. Add the swap file to the /etc/fstab file so that it is automatically mounted at boot time:

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

6. Reboot the VM.

After rebooting the VM, you should have a swap file of 8 GB in size that is available to your system.

Conclusion

A swap file acts as a safety net for systems that might run out of physical RAM, and it's particularly beneficial for systems with limited memory. However, it's not always necessary, especially in well-resourced, high-performance environments. Careful consideration of the specific needs and constraints of your system will help you determine whether or not to use a swap file. If in doubt, monitoring system memory usage over time can provide valuable insights into whether a swap file might be beneficial for your particular use case.