securetty(5) -- Linux man page
NAMEsecuretty - file which lists ttys from which root can log in
DESCRIPTIONThe file /etc/securetty is used by (some versions of) login(1). The file contains the device names of tty lines (one per line, without leading /dev/) on which root is allowed to login. See login.defs(5) if you use the shadow suite.
SEE ALSOlogin(1), login.defs(5)