@Dragonmouth,

Yes, if no space is left on the disk, you must add a new hard disk and create a space for a swap.

“What if there is no free space?”

Straw man argument. If there is no free space available on the system you cannot set up swap space, either. It’s time to get a bigger disk or another disk.

This can be dangerous if someone misses types the command as:

$ sudo rm -rf / swap.info

(note space between the "/" and “swap.info”.

I managed to do this on a production SCO server 25 years ago late on a Friday afternoon. Totally ruined my weekend, but learned to only use “rm -r” when you really mean it.

In my opinion, it is a bad idea to teach using “rm -rf” without explaining that if this command is miss-typed, you may remove your entire file system, because the command that you are issuing is: remove recursively, without bothering me with questions, because I definitely want to do this.

In your case, you are doing, so you have to write permission on the file (no need for -f), and it is a file, not a directory (no need for -r).

The safer command to teach is
sudo rm /swap.img

@Dragonmouth,

Yes, you can setup the Swap partition, only if there is a Free space available on the filesystem. What if there is no free space? in this case adding swap space is useful when you running out of memory..