nologin5
Prevent unprivileged users from logging into the system
Overview
If the file /etc/nologin exists and is readable, login(1) will allow access only to root. Other users will be shown the contents of this file and their logins will be refused. This provides a simple way of temporarily disabling all unprivileged logins.
Files
/etc/nologin
Releases
19 releases since Debian 1.1 (Buzz); the text changed 15 times.