libpam-tmpdir ships the file `/usr/lib/tmpfiles.d/libpam-tmpdir.conf`
with the following contents:
----
#
# Ensure /tmp/user exists with strict permissions.
#
# If you want more lenient permissions, feel free to change this to 0755.
d /tmp/user 0711 root root -
----
The `d` at the beginning of the line indicates that this directory
should be created, but it is not cleaned on boot. For that, the `D`
directive is required instead. As a result, if one does not have `/tmp`
as a tmpfs, `/tmp/user` is never cleaned and temporary files accumulate.
I noticed this because I've disabled using `/tmp` as a tmpfs, since I
use it frequently for temporary storage and only rarely reboot, so with
a tmpfs I run out of space. As a consequence, `/tmp/user` had not been
cleaned since late December and, after providing a corrected tmpfiles.d
file and rebooting, my system took 4 minutes and 4 seconds just to clean
up temporary files, even with a high-speed NVMe drive.
Could you adjust this file in the next version to use the `D` directive
so this is automatically cleaned on boot? That would preserve the
traditional behaviour in Debian that temporary files are cleared on
boot.