NAME
login
—
log into the computer
SYNOPSIS
login |
[-fp ] [-h
hostname] [-L
local-addr] [-R
remote-addr] [-u
username] [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 normally done via passwords, though
external authentication mechanisms may be used (see
login.conf(5)). To specify the alternate authentication
mechanism style, the string
:style is appended to the user name (i.e.,
user:style).
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 superuser. -h
hostname- Specifies the host from which the connection was received. This option may only be used by the superuser.
-L
local-addr- The
-L
option specifies the local address of a socket. This information is passed on to any classify script (see login.conf(5)). -p
- By default,
login
discards any previous environment. The-p
option disables this behavior. -R
remote-addr- The
-R
option specifies the remote address of a socket. This information is passed on to any classify script (see login.conf(5)). -u
username- Specifies the remote user that initiated the connection. This option may only be used by the superuser.
If the file /etc/nologin exists (and the
“ignorenologin” boolean is not set in the user's login class),
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/fbtab exists,
login
changes the protection and ownership of
certain devices specified in this file.
If the file /var/log/failedlogin exists,
login
will record failed login attempts in this
file.
Immediately after logging a user in, login
displays the system copyright notice, the date and time the user last logged
in, the date and time of the last unsuccessful login (if the file
/var/log/failedlogin exists), 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 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 standard shells,
csh(1) and sh(1), do not fork before executing the
login
utility.
Note that if login
is invoked by a
non-root user, it will execute
su(1)
in login
emulation mode instead.
ENVIRONMENT
login
sets the following environment
variables:
HOME
- The user's home directory, as specified by the password database.
SHELL
- The user's shell, as specified by the password database.
TERM
- The user's terminal type, if it can be determined.
LOGNAME
- The user's login name.
USER
- Same as
LOGNAME
. MAIL
- The user's mailbox.
REMOTEHOST
- The name of the host from which the user logged in, if the
-h
flag was specified. REMOTEUSER
- The name of the remote user who initiated the connection, if the
-u
flag was specified.
Other environment variables may be specified in /etc/login.conf via the “setenv” capability.
FILES
- /etc/fbtab
- changes device protections
- /etc/login.conf
- login configuration
- /etc/motd
- message-of-the-day
- /etc/nologin
- disallows logins
- /var/log/failedlogin
- failed login account records
- /var/log/lastlog
- last login account records
- /var/log/wtmp
- login account records
- /var/mail/user
- system mailboxes
- /var/run/utmp
- current logins
- .hushlogin
- makes login quieter
SEE ALSO
chpass(1), passwd(1), su(1), telnet(1), readpassphrase(3), setusercontext(3), fbtab(5), login.conf(5), utmp(5), environ(7)
HISTORY
A login
utility appeared in
Version 3 AT&T UNIX.