LOGIN(1) BSD General Commands Manual LOGIN(1)NAMElogin — authenticate users and set up their session environment
SYNOPSISlogin [-Ffps] [-a address] [-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. If the user can be authenticated via S/Key, then
the S/Key challenge is incorporated in the password prompt. The user
then has the option of entering their Kerberos or normal password or the
S/Key response. Neither will be echoed.
The options are as follows:
-a The -a option specifies the address of 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.
-F The -F option acts like the -f option, but also indicates to
login that it should attempt to rewrite an existing Kerberos 5
credentials cache (specified by the KRB5CCNAME environment vari‐
able) after dropping permissions to the user logging in. This
flag is not supported under pam(8).
-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.
-s Require a secure authentication mechanism like Kerberos or S/Key
to be used. This flag is not supported under pam(8).
If a user other than the superuser attempts to login while the file
/etc/nologin exists, login displays its contents to the user and exits.
This is used by shutdown(8) to prevent normal users from logging in when
the system is about to go down.
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. login then records an entry in the
wtmp(5) and utmp(5) files, executes site-specific login commands via the
ttyaction(3) facility with an action of "login", 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).
The user's login experience can be customized using login class capabili‐
ties as configured in /etc/login.conf and documented in login.conf(5).
The standard shells, csh(1) and sh(1), do not fork before executing the
login utility.
FILES
/etc/login.conf login class capability database
/etc/motd message-of-the-day
/etc/nologin disallows non-superuser logins
/var/run/utmp list of 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 ALSOchpass(1), newgrp(1), passwd(1), rlogin(1), skey(1), getpass(3),
ttyaction(3), login.conf(5), passwd.conf(5), utmp(5), environ(7),
kerberos(8), pam(8)HISTORY
A login appeared in Version 6 AT&T UNIX.
TRADEMARKS AND PATENTS
S/Key is a trademark of Bellcore.
BSD November 19, 2008 BSD
