nologin(5) File Formats Manual nologin(5)

nologin - prevent unprivileged users from logging into the system

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.

/etc/nologin

login(1), shutdown(8)

2022-10-30 Linux man-pages 6.02