nologin (5) - Linux Man Pages
nologin: prevent unprivileged users from logging into the system
nologin - prevent unprivileged users from logging into the system
DESCRIPTIONIf 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.
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