systemd-user-sessions.service, systemd-user-sessions - Permit user logins after
boot, prohibit user logins at shutdown
systemd-user-sessions.service
/lib/systemd/systemd-user-sessions
systemd-user-sessions.service is a service that controls user logins through
pam_nologin(8). After basic system initialization is complete, it
removes /run/nologin, thus permitting logins. Before system shutdown, it
creates /run/nologin, thus prohibiting further logins.
systemd(1),
systemd-logind.service(8),
pam_nologin(8)