How To Create a New Swap File

Sometimes the amount of RAM that your system has is not enough for the applications you run, or maybe you're running some poorly-written software that runs fine within the RAM you have but complains about low amounts of swap space. In either case, you'll need to add more “swap” space - also known as “virtual memory” - to your system.

The guide below will demonstrate how to do this. We will be moving forward with the following assumptions (both of which will be up to you to decide):

• You want your new swap file to be 16GB in size.
• You wish to create the swap file at /var/cache/swap/swapfile.

The first thing you need to do is create the swapfile (obviously!). Simply create the directory (if it doesn't already exist), then use fallocate to create your new swap file:

mkdir -p /var/cache/swap
fallocate -l 16G /var/cache/swap/swapfile

Now we need to set permissions on the swap file so that only root can read/write to it. Simply run:

chmod 600 /var/cache/swap/swapfile

And then run mkswap to create the swap space:

mkswap /var/cache/swap/swapfile

At this point, we have a swap file located at /var/cache/swap/swapfile that is 16GB in size and is ready to go.

Finally we need to configure our system to load the swap at boot time, and then load the swap space on our running system (or just reboot, either works). Open up /etc/fstab in your preferred text editor, and either

Now you can either reboot to load the new swap space, OR you can run the following command to load it on the running system:

swapon /var/cache/swap/swapfile

Of course, anything you do is worth testing. To do that, simply run free -m to show your system's memory usage. You should see something like the picture below:

Pic Obviously your system stats will look different than mine do depending on the configuration of your system, but you should see a total virtual memory figure that resembles 16GB (16384MB) of virtual memory, or at least whatever amount of space you decided to give to it. Also note that if you just ran the swapon command instead of rebooting and you're migrating from one swap file to another, you may see the total size of the two swap files. To correct this, simply run swapoff </path/to/old/swapfile and you should see a total virtual memory that corresponds to your new swap file.