Swap space is a reserved area on disk used when physical RAM is full. When a Linux system runs out of RAM, inactive pages are moved from RAM to the swap space — keeping the system running instead of crashing.

This is important for my old laptop, which only has 4 GB of RAM and starts to crawl under load. Adding a larger swap file gives it some breathing room.

Quick Steps

  1. Turn off swap processes
  2. Resize the swap file
  3. Make the file usable as swap
  4. Activate the swap file
  5. Verify the swap size

Step-by-Step

Step 1 — Turn off swap

sudo swapoff -a

Step 2 — Create a new swap file (8 GB = double the RAM)

sudo dd if=/dev/zero of=/swapfile bs=1M count=8192

bs=1M count=8192 creates an 8 GiB file. Adjust count for a different size (e.g. count=4096 for 4 GiB).

Step 3 — Set correct permissions

sudo chmod 0600 /swapfile

Step 4 — Format it as swap

sudo mkswap /swapfile

Step 5 — Activate it

sudo swapon /swapfile

Step 6 — Verify

grep Swap /proc/meminfo

Or check the file size directly:

ls -lh /swapfile

Make It Permanent (survive reboots)

Add the swap file to /etc/fstab so it activates automatically on boot:

# /etc/fstab — add this line at the end
/swapfile swap swap sw 0 0

Alternative: Swap on a Separate Partition or Path

If you want to store the swap file on a different drive (e.g. a fast HDD), change the path accordingly:

# Create the file on a specific drive
sudo dd if=/dev/zero of=/media/fasthdd/swapfile.img bs=1024 count=1M

# Format it
sudo mkswap /media/fasthdd/swapfile.img

# Activate it
sudo swapon /media/fasthdd/swapfile.img

And in /etc/fstab:

/media/fasthdd/swapfile.img swap swap sw 0 0

Confirm Everything is Working

cat /proc/swaps

Expected output:

Filename                          Type    Size      Used  Priority
/swapfile                         file    8388604   2724  -1

grep 'Swap' /proc/meminfo

Expected output:

SwapCached:     4772 kB
SwapTotal:   8388604 kB
SwapFree:    8355812 kB

If SwapTotal shows your new size, you’re done. ✓