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Create and remove swap files

There are two basic types of memory: Random Access Memory (RAM) and swap files.

The following table shows the recommended swap size based on your RAM and whether you choose hibernation. Hibernation requires more space because it saves the system state when you shut down and restores it when you restart.

Remember that you'll need a large page file if your system has hibernation enabled, as it writes the contents of the RAM to swap on shutdown.

How to Create a Swap File and Increase Swap Space

Verify the current swap file size. You can use any of the following commands to determine the size of the existing swap file:

free -m
swapon -s
swapon -show

Now that we've verified it's safe to proceed, and we can craft our swap file. There are a few ways to do this, but the easiest is via the fallocate program, which lets us allocate the exact size we want our swapfile to be. As mentioned earlier, our server has 1 GB of RAM. We're going to set our swapfile to 2 GB because we have plenty of free space, but 1 GB of the swap would likely work just fine if we didn't:

sudo fallocate -l 2G /swapfile

As we didn't specify a folder, our swap file will be placed in our root directory, which is what we want. The command won't give any output, so you can make sure the swap space was actually reserved with:

ls -lh /swapfile

In our case, the command returns:

rw-r--r-- 1 root root 2.0G Aug 15 12:47 /swapfile

However, though we have space reserved for our swapfile, our system hasn't yet be told this is where we want to it store information when out of memory. Before we do so, we want to make sure nobody but root can modify the file. Otherwise, an attacker could potentially use the file to perform an attack or steal information. Set the permissions with:

sudo chmod 600 /swapfile

Now verify that change using the same command as earlier: ls -lh /swapfile

The output should have changed from rw-r--r-- 1 root root to -rw------- 1 root root 2.0G Aug 15 12:47 /swapfile, indicating that now only root has the read and write flags enabled.

With that done, dedicate the file as swap space by entering:

sudo mkswap /swapfile

The output should say something like:

Setting up swapspace version 1, size = 2 GiB (2147479552 bytes) no label, UUID=f9429158-ec78-4dce-98c0-986167b47016

Now we just need to enable the swap file:

sudo swapon /swapfile

And verify that it's available via the check commands from earlier:

sudo swapon --show

Make it permanent:

echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

Last reboot to update change.

Remove Swap File

Run the following command to reactivate the swap file:

swapoff -v /swapfile

Remove the entry

sudo nano /etc/fstab

Run the following command to remove the swapfile:

rm -f /swapfile

Last reboot to update change.

Reference & commands pick from:

https://bitlaunch.io/blog/how-to-create-and-adjust-swap-space-in-ubuntu-20-04/

https://askubuntu.com/questions/1066358/increasing-the-swap-space-on-ubuntu

https://docs.rackspace.com/support/how-to/create-remove-swap-file-in-ubuntu/

https://www.digitalocean.com/community/tutorials/how-to-add-swap-space-on-ubuntu-20-04