LOGIN(1)

NAME
login - log into the computer

SYNOPSIS
login [-fp] [-h hostname] [user]

DESCRIPTION
The login utility logs users (and pseudo-users) into the computer system.

If no user is specified, or if a user is specified and authentication of the user fails, login prompts for a user name. Authentication of users is done via passwords.

The options are as follows:

-f  The -f option is used when a user name is specified to indicate that proper authentication has already been done and that no password need be requested. This option may only be used by the super-user or when an already logged in user is logging in as themselves.

-h  The -h option specifies the host from which the connection was received. It is used by various daemons such as telnetd(8). This option may only be used by the super-user.

-p  By default, login discards any previous environment. The -p option disables this behavior.

If the file /etc/nologin exists, login displays its contents to the user and exits. This is used by shutdown(8) to prevent users from logging in when the system is about to go down.

If the file /etc/login.access exists, login checks to see if the user and host pair are specifically allowed or denied access. Login access may also be controlled via the login class, which provides allow and deny records based on time, tty and remote host name.

If the file /etc/fbtab exists, login changes the protection and ownership of certain devices specified in this file.

If the file /etc/skeykeys exists, login will offer S/key password validation if the user has an entry in the file. /etc/skey.access controls from which hosts and/or networks the use of S/key passwords are obligated.

Immediately after logging a user in, login displays the system copyright notice, the date and time the user last logged in, the message of the day as well as other information. If the file “.hushlogin” exists in the user's home directory, all of these messages are suppressed. This is to simplify logins for non-human users, such as uucp(1). Login then records an entry in the wtmp(5) and utmp(5) files and executes the user's command interpreter.

Login enters information into the environment (see environ(7)) specifying the user's home directory (HOME), command interpreter (SHELL), search path (PATH), terminal type (TERM) and user name (both LOGNAME and USER). Other environment variables may be set due to entries in the login class capabilities database, for the login class assigned in the user's system passwd record. The login class also controls the maximum and current process resource limits granted to a login, process priorities and many other aspects of a user's login environment.

The standard shells, csh(1) and sh(1), do not fork before executing the login utility.

FILES
/etc/fbtab
    changes device protections
/etc/login.access
    login access control table
/etc/login.conf
    login class capabilities database
/etc/motd
    message-of-the-day
/etc/nologin
    disallows logins
/etc/skey.access
    skey password control table
/etc/skeykeys
    skey password database
/var/run/utmp
    current logins
/var/log/lastlog
    last login account records
/var/log/wtmp
    login account records
/var/mail/user
    system mailboxes
.hushlogin
    makes login quieter

SEE ALSO
chpass(1), passwd(1), rlogin(1), skey(1), getpass(3), fbtab(5), login.access(5), login.conf(5), skey.access(5), utmp(5), environ(7), nologin(8)

HISTORY
A login utility appeared in AT&T UNIX.