Comment # 16 on bug 966671 from Michal Kube��ek

Created attachment 725704 [details]
/etc/tmpfiles.d/tmp.conf

Found one more difference: on the 42.2 machine exhibiting the bug, there is
file /etc/tmpfiles.d/tmp.conf (attached). According to rpm, it's not owned by
any package but its contents seems to suggest that it once was part of systemd.
Perhaps it's a leftover from older systemd version (from 13.1).

Tried to look into tmpfiles.d(5) but I'm still confused...

  x /tmp/* - - - - root

Should mean only files/directories under /tmp owned by root should be omitted;
but I couldn't find any rule in /etc/tmpfiles.d or /usr/lib/tmpfiles.d that
would say something under /tmp should be deleted.

On the Tumbleweed system without this file, nothing is probably cleaned
automatically; there is even a file from September 2015 (not touched since)
owned by regular user in its /tmp (/tmp is not on tmpfs there).