Nologin

Nologin is a command provided by the util-linux package. It is used as a shell for users who are not allowed to log in because their account has been disabled by the system administrator. The program prints a polite message that the requested user account is not available and exits with an error.

The nologin command should not be confused with the file /etc/nologin. When this file is present on a system, no one except root can log in. The system administrator, working as root, can create this file when it is necessary to isolate the system for maintenance. The file is created automatically when the shutdown command is invoked.