Cleaning up space
If your system runs out of space, you may an emergency option to get back some bit of space, and investigate what's taking up space
Execute the basic-space-cleanup tool
One may use the following command, to perform basic space cleanup (apt, journalctl, logs, ...) :
sudo yunohost tools basic-space-cleanup
Additionaly, you may want to cleanup YunoHost operation logs if they are taking too much space, cf this issue.
Explore what's taking up space
Install ncdu:
sudo apt install ncdu
Then use it to scan the filesystem and have a dynamic, browsable report of what's using space:
ndcu /
or ncdu /var/, for example to scan only /var/