How to add Swap space on Ubuntu

Create a file and preallocate size. In the following example we allocate 4GB

$ sudo fallocate -l 4G /swapfile

The prompt will return:

$ ls -lh /swapfile
-rw-r--r-- 1 root root 4.0G Feb  8 08:50 /swapfile

Enable SWAP file

We need to enable it before to use it, but first let’s make sure the permissions are right

$ sudo chmod 600 /swapfile

Check if the permissions were applied correctly:

$ ls -lh /swapfile
-rw------- 1 root root 4.0G Feb  8 08:50 /swapfile

So we have only read write only enabled for root.

Now that everything is correct we tell our OS to use this file as swap by typing:

$ sudo mkswap /swapfile

Setting up swapspace version 1, size = 4 GiB (4294963200 bytes)
no label, UUID=9457c9c4-96eb-4fd8-821e-dfdf202d7f45

All we have to do now is to *enable it:

$ sudo swapon /swapfile

Verify if the procedure was correct:

$ sudo swapon -s
Filename				Type		Size	Used	Priority
/swapfile               file    	4194300	  0	        -2

Make swap permanent

We have the swap activated, but after reboot it will be deactivated so we need to modify the fstab file

$ sudo nano /etc/fstab

At the end of the file add

/swapfile   none    swap    sw    0   0

Save and close the file when you are finished.

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