Title, I installed my system with two partitions, a big one and a small one for the OS. I figured 100GB would be enough for the OS one, but apparently not as it keeps filling up. Steam keeps filling it for some reason, something to do with Proton. I know that messing with partition sizes has a risk of data loss and all that, and I don’t really want to lose parts of my OS.
You’d have to shrink the other one first, unless you left free space. If you used lvm you should be able to do this online, else I’d take it offline and boot gparted.
Although you can probably just redirect steam to the other partition, with a symlink if it doesn’t let you change the dir.
If you make any partition changes, make sure you have a separate working backup of any data you can’t afford to lose.