The easiest solution would be to add a swap file. If you are already encrypting your root file system, I would not bother with an encrypted swap file, which is only a little more difficult, but it is slower. The advantage of a swap file is that you can remove it later to regain the disk space. And the disk is already encrypted!
The steps are straightforward. First, make the file. For example, this would make 1GB of new swap:
sudo dd if=/dev/zero of=/swapfile bs=1024 count=1024k
dd to put the new swap file in
/swapfile. You can call it anything you want. You can add multiple swap files, too. For recent Linux kernels, the speed is the same as a swap partition.
Then, you need to format the swap file as swap space, like so:
sudo mkswap /swapfile
This command will give you some output like:
Setting up swapspace version 1, size = 1048576 KiB
no label, UUID=83352590-ef57-49f5-84c4-7fb847e4e4e0
And that's your new swap file. Finally, you need to activate the swap on your machine using the following command:
sudo swapon /swapfile
sudo swapon -s should show you both the swap partition and the swap file.
I then recommend adding some security by changing permissions as follows:
sudo chown root:root /swapfile
sudo chmod 0600 /swapfile
If all seems good so far, you can add the swap file permanently by adding the the following line to
/etc/fstab using your favorite editor:
/swapfile none swap sw 0 0
You can add multiple swap files, of course. And you can remove the swap file by using
sudo swapoff /swapfile.
Hope this helps.