Save your frozen Linux Server: How to add swap space to Ubuntu

If you don’t want to read the complete thing and just get this done quick. Then just copy paste the below lines... but before that replace 1G in second command with however much space you like (probably consider hitting 👏 if it helped you)

sudo swapon --show                  
sudo fallocate -l 1G /swapfile      # allocate 1G of swap space
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
sudo swapon --show
sudo echo '/swapfile swap swap defaults 0 0' | sudo tee -a /etc/fstab

When do I add Swap Space ?

Whenever I’m working on a hobby project and I want to setup a new Linux server with Ubuntu OS, I do this as the first step.
I mostly use small instances/VMs in free tier 😝 from AWS or OCI or some other cloud vendor. These VMs have limited amount of RAM and often freeze due to out of memory issues when I run automated github actions or something which puts pressure on memory all of a sudden.

Adding swap right after creating server has helped me avoid frozen instances and sometimes even deleting the instance and setting up a new from sacratch again because the server froze and couldn’t come up even on reboot.

Step-1: Check some stuff

Check if swap is enabled
Below output is after I have already added swap. If there’s no swap, output will be empty.

sudo swapon --show                  # show current swap details

NAME      TYPE SIZE  USED PRIO
/swapfile file   2G 25.5M   -2

Check available Memory
️❗Take a note of available memory (RAM) from here.
Shows 949Mi (~1G) for me (Ignore the Swap bit).

free -h
               total        used        free      shared  buff/cache   available
Mem:           949Mi       263Mi        95Mi       0.0Ki       590Mi       518Mi
Swap:          2.0Gi        25Mi       2.0Gi

Check available disk space
Just see how much free space you have on disk to use for swap. Looks like I have enough 🆓disk space

df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/root        20G  6.7G   13G  35% /
tmpfs           475M     0  475M   0% /dev/shm
tmpfs           190M  972K  189M   1% /run
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/xvda15     105M  6.1M   99M   6% /boot/efi
tmpfs            95M  4.0K   95M   1% /run/user/1000

Step-2: Allocate Swap File

Usually I keep allocate swap space which is 1–2x the memory available on system. But it could be higher also.
Since I have ~1G RAM, I’m allocating swapfile of size 1G. Change to whatever you like

sudo fallocate -l 1G /swapfile      # allocate 1G of swap space

Step-3: Secure swapfile by changing

sudo chmod 600 /swapfile

Step-4: Convert swap file to swap area

sudo mkswap /swapfile

Step-5: Enable swap

sudo swapon /swapfile

Step-6: Make sure swap stays even after reboot

To make changes we did till now permanent, either
paste this /swapfile swap swap defaults 0 0 at end of this file /etc/fstab

OR, just run this 🙌🏻

sudo echo '/swapfile swap swap defaults 0 0' | sudo tee -a /etc/fstab

Thats it done 🙌

Now if you wish to check stuff you can run either this free -h or this swapon --show command.

Note-1: If you ever wish to disable swap, you need to do this

1. Turn off swap sudo swapoff -v /swapfile
2. Open the file /etc/fstab and delete this entry /swapfile swap swap defaults 0 0
3. Delete the swap file sudo rm /swapfile

I also keep all above steps handy in my guides repo on github.

Note-2: There are two ways of adding swap space

1. Swap file
2. Swap partition

We have used Swap file here. I’ve never used the other one since this option was just enough for me always. If you wish, feel free to explore the other one.

Hope this helped😀… consider hitting 👏. Saved your precious time !! Appreciate my efforts buy me a tea ☕. You can also find me on Linkedin and say 👋.