This is weird, because gdm3 (the display manager required by gnome-core, which is required by gnome-terminal) depends upon libpam-modules, and this package owns /etc/security.
If I got this correctly, the real problem is that systemd ignores the ulimits set via pam. > systemd (user) services run in a separate, clean context though, > that's why there are separate knobs for this. Sorry to say, but it doesn't seem that clean to me. Regards Harri