nologin — politely refuse a login
nologin displays a message that an account is not available and exits non-zero. It is intended as a replacement shell field to deny login access to an account.
If the file /etc/nologin.txt exists, nologin displays its contents to the user instead of the default message.
The exit code returned by nologin is always 1.
nologin is a per-account way to disable login (usually used for system accounts like http or ftp). nologin(8) uses /etc/nologin.txt as an optional source for a non-default message, the login access is always refused independently of the file.
pam_nologin(8) PAM module usually prevents all non-root users from logging into the system. pam_nologin(8) functionality is controlled by /var/run/nologin or the /etc/nologin file.
The nologin command is part of the util-linux package and is available from Linux Kernel Archive