[KORraN]

Isn't this the feature of /tmp? I set my default download location in Firefox to /tmp exactly for this reason, so that all the junk gets automatically removed after some time. Also, whenever I need a temporary Python script or test a package, I create a venv under /tmp.

[superkuh]

On boot has been the standard for a long time and is still the most common. I am personally surprised to hear that now Debian and some distros do it via various automated ways at time intervals.

[saint_yossarian]

It's a systemd thing, see `man systemd-tmpfiles`.

[rfmoz]

It is done by a systemd timer unit