Linux systems rely on RAM for running applications smoothly. But what happens when your memory runs out? That’s where swap space comes in. A swap file acts as backup memory on your disk, preventing crashes when your system is under heavy load.

Unlike swap partitions, swap files are flexible — you can create, resize, or delete them easily without touching your disk partitions.

In this guide, we’ll cover:
✅ What swap is
✅ Why swap is important
✅ How to create a swap file in Linux
✅ Distro-specific notes (Ubuntu, Fedora, AlmaLinux, etc.)
✅ Tuning tips for better performance

💡 What is Swap?

• Swap = disk space used as virtual memory when RAM is full.

• Keeps your system running under heavy load.

• Prevents “Out of Memory (OOM)” errors.

• Should not replace physical RAM — it’s slower than real memory.

👉 Think of swap like an emergency spare tire 🚗 — not ideal for everyday driving, but it saves you when you’re stuck.

🔹 Step 1: Create the Swap File

Option 1: Using fallocate (faster)

sudo fallocate -l 1G /swapfile

Option 2: Using dd (more compatible)

sudo dd if=/dev/zero of=/swapfile bs=1M count=1024

👉 This creates a 1 GB swap file. Adjust 1G or count=1024 depending on your needs.

🔹 Step 2: Set Secure Permissions 🔐

Only root should read/write the swap file:

sudo chmod 600 /swapfile

🔹 Step 3: Format as Swap 📦

sudo mkswap /swapfile

🔹 Step 4: Enable the Swap 🚀

sudo swapon /swapfile

Check if it’s active:

swapon --show
free -h

🔹 Step 5: Make Swap Permanent 🔄

Add entry in /etc/fstab:

/swapfile none swap sw 0 0

This ensures swap activates automatically after every reboot.

🔹 Step 6: Adjust Swappiness (Optional ⚙️)

The swappiness value (0–100) tells Linux how aggressively it uses swap.

• 0 → avoid swap unless absolutely needed.

• 60 (default) → balanced.

• 10 → recommended for desktops/servers (prefer RAM).

Check current value:

cat /proc/sys/vm/swappiness

Set swappiness to 10:

sudo sysctl vm.swappiness=10

Make it permanent by adding to /etc/sysctl.conf:

vm.swappiness = 10

🔎 Distro-Specific Notes

🐧 Ubuntu / Debian

• Newer Ubuntu versions often create a swap file by default.

• Check with:

  swapon --show
  

🐯 Fedora

• Works out of the box with fallocate.

🟤 AlmaLinux / RHEL / CentOS

• If SELinux complains, apply context:

  sudo chcon system_u:object_r:swapfile_t:s0 /swapfile
  

🐤 Arch Linux

• Swap file is often preferred over partitions for flexibility.

🧪 Real-World Example Scenarios

✔️ Low-RAM VPS (1–2 GB)
Create a 2 GB swap file to prevent out-of-memory errors when compiling code.

✔️ Desktop Optimization
Lower swappiness to 10 to keep apps in RAM and reduce lag.

✅ Verify Everything

Run:

free -h

Example output:

              total        used        free      shared  buff/cache   available
Mem:           2.0G        1.2G        200M        100M        600M        600M
Swap:          1.0G          0B        1.0G

🎉 Done! You now have a working swap file in Linux.

🔚 Conclusion

A Linux swap file is a simple yet powerful way to give your system breathing room under heavy workloads. Whether you’re on Ubuntu, Fedora, AlmaLinux, or Arch, the steps are straightforward.

👉 Use swap as a safety buffer, not a replacement for RAM.
👉 Tune swappiness for optimal performance.
👉 Monitor usage with htop or vmstat.

With a properly configured swap file, your Linux system will run smoother, safer, and more resilient 🚀.