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Francis Ndungu

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How to Expand your System RAM with Swap Space on Rocky Linux 9

Introduction

Swap space is a Linux feature that acts as additional virtual memory by using disk storage. When your system's physical RAM is fully utilized, swap space temporarily stores less-used data, ensuring smooth system performance and preventing crashes during heavy workloads.

This guide shows you how to create and configure swap space on Rocky Linux 9 to expand your system RAM and efficiently run memory-intensive applications.

Prerequisites

Before you begin:

Deploy a Digital Ocean VPS server running Rocky Linux 9.
Create a non-root sudo user. For guidance, refer to the following guide:
- How to Create a Non-Root Sudo User on Rocky Linux.

Check for Existing Swap Space

SSH into your server as a non-root sudo user.
Check whether a swap space is already active.
console
```
$ sudo swapon --show
```
If there's no output, it means no swap space is currently active. If swap is already enabled, you'll see output like this.
```
NAME      TYPE      SIZE   USED   PRIO
/swapfile file      2G     0B     -2
```
If swap exists but you'd prefer to create a new one:
- Disable the current swap space:
  console
```
$ sudo swapoff -a
```
- Delete the swap file (if applicable):
  console
```
$ sudo rm /swapfile
```

Allocate Disk Space for Swap

Decide how much swap space to allocate based on your system’s RAM and workload:

For systems with ≤ 2GB RAM, set swap to 2× RAM.
For systems with > 2GB RAM, set swap to 1–1.5× RAM.

For instance:

A system with 1GB RAM benefits from a 2GB swap.
A system with 4GB RAM may need 4–6GB swap.

To allocate swap space:

Create a swap file. Replace 2G with your desired size.
console
```
$ sudo fallocate -l 2G /swapfile
```
If fallocate isn’t available, use:
console
```
$ sudo dd if=/dev/zero of=/swapfile bs=1M count=2048
```

. Verify the file exists.

console

$ ls -lh /swapfile

Output:

-rw------- 1 root root 2.0G ... /swapfile

Secure the Swap File

Protect sensitive data in the swap file by restricting access to the root user.

Adjust permissions.
console
```
$ sudo chmod 600 /swapfile
```

Verify the permissions.

console

$ ls -lh /swapfile

Output:

-rw------- 1 root root 2.0G ... /swapfile

Set Up the Swap File

Format the file as a swap space.
console
```
$ sudo mkswap /swapfile
```
Activate the swap file.
console
```
$ sudo swapon /swapfile
```

Ensure the swap file is active.

console

$ sudo swapon --show

Output:

NAME      TYPE      SIZE   USED   PRIO
/swapfile file      2G     0B     -2

Make the Swap File Permanent

The next step is ensuring your swap space is automatically enabled at boot.

Open the /etc/fstab file with a text editor.
console
```
$ sudo nano /etc/fstab
```
Add this line to the end of the file.
INI
```
/swapfile none swap sw 0 0
```
Save and close the file by pressing Ctrl + X, Y , and Enter.

Optimize Swap Usage

Swappiness determines how aggressively Linux uses swap space. The default value is 60, but you can adjust it for your needs:

Low RAM (≤ 4GB): Use higher swappiness (For instance, 60) to prioritize disk usage.
High RAM (≥ 8GB): Lower the swappiness (For instance, 10–20) to favor RAM.
Check the current swappiness value.
console
```
$ cat /proc/sys/vm/swappiness
```
Output:
```
60
```
Temporarily set swappiness to 10.
console
```
$ sudo sysctl vm.swappiness=10
```
Edit /etc/sysctl.conf for a permanent change.
console
```
$ sudo nano /etc/sysctl.conf
```
Add this line.
INI
```
vm.swappiness=10
```
Apply the settings:
console
```
$ sudo sysctl -p
```

General Swappiness Recommendations

Systems with Low RAM (≤ 4GB)

Use a swappiness of 60 to offload inactive data to disk.

Systems with High RAM (≥ 8GB)

Use a swappiness of 10–20 to minimize disk usage.

SSD vs HDD

SSD: Use swappiness 30–40 for faster swap performance.
HDD: Use swappiness 10–20 to reduce bottlenecks.

Conclusion

This guide explained how to set up and optimize swap space on Rocky Linux 9, including verifying existing swap, creating and securing a swap file, making it permanent, and tuning swappiness for better performance. With properly configured swap, your system can now handle memory-intensive tasks smoothly and efficiently.

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