nologin
nologin displays a message that an account is not available and exits
non-zero. It is intended as a replacement shell field for accounts that
have been disabled.
If the file /etc/nologin.txt exists, nologin displays its contents to the
user instead of the default message.
login(1)
The nologin command appeared in 4.4BSD.
BSD Experimental February 15, 1997 1