login(1) login(1)
NAME
login - sign on
SYNOPSIS
login [name[env-var ...]]
DESCRIPTION
The login command is used at the beginning of each terminal
session and allows you to identify yourself to the system.
It may be invoked as a command or by the system when a
connection is first established. Also, it is invoked by the
system when a previous user has terminated the initial shell
by typing a CONTROL-d to indicate an ``end-of-file''.
If login is invoked as a command, it must replace the
initial command interpreter. This is accomplished by
typing:
exec login
from the initial shell, if it is the Bourne shell, sh(1), or
the Korn shell, ksh(1). For the C shell, csh(1), you may
just type:
login [user]
login asks for your user name (if not supplied as an
argument), and, if appropriate, your password. Echoing is
turned off (where possible) during the typing of your
password, so it will not appear on the written record of the
session.
At some installations, an flag option may be invoked that
will require you to enter a second dialup password. This
will occur only for dial-up connections, and will be
prompted by the message dialup password:. Both passwords
are required for a successful login.
If you do not complete the login successfully within a
certain period of time (e.g., one minute), you are likely to
be disconnected silently.
After a successful login, accounting files are updated, the
procedure /etc/profile is performed, the message-of-the-day,
if any, is printed, the user-ID, the group-ID, the working
directory, and the command interpreter (usually sh(1)) is
initialized, and the file .profile in the working directory
is executed, if it exists. These specifications are found
in the /etc/passwd file entry for the user. To indicate
that this invocation of the command interpreter is the login
shell, the name of the interpreter is prefixed with a minus
sign, -, (e.g., -sh). If this field in the password file is
empty, then the default command interpreter, the Bourne
shell (/bin/sh) is used. If this field is *, then a
chroot(2) is done to the directory named in the directory
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login(1) login(1)
field of the entry. At that point login is re-executed at
the new level, which must have its own root structure,
including /etc/login and /etc/passwd.
The basic environment (see environ(5)) is initialized to:
HOME=your-login-directory
PATH=:/bin:/usr/bin
SHELL=last-field-of-passwd-entry
MAIL=/usr/mail/your-login-name
TZ=timezone-specification
The environment may be expanded or modified by supplying
additional arguments to login, either at execution time or
when login requests your login name. The arguments may take
either the form xxx or xxx=yyy. Arguments without an equals
sign are placed in the environment as
Ln=xxx
where n is a number starting at 0 and is incremented each
time a new variable name is required. Variables containing
an = are placed into the environment without modification.
If they already appear in the environment, then they replace
the older value. There are two exceptions. The variables
PATH and SHELL cannot be changed. This prevents people,
logging into restricted shell environments, from spawning
secondary shells that are not restricted. Both login and
getty understand simple single-character quoting
conventions. Typing a backslash in front of a character
quotes it and allows the inclusion of such things as spaces
and tabs.
EXAMPLE
At the beginning of each terminal session, the following
sort of message is displayed on the screen:
Oreo 68000
:login:
to which a user name is the appropriate response.
FILES
/bin/login
/etc/utmp accounting
/etc/wtmp accounting
/usr/mail/your-name mailbox for user your-name
/etc/motd message-of-the-day
/etc/passwd password file
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login(1) login(1)
/etc/profile systemwide personal profile (sh(1))
/etc/cshrc systemwide personal csh startup (csh(1))
.profile personal profile (sh(1))
.login personal csh startup used at login time
(csh(1))
.cshrc personal csh startup (csh(1))
.logout personal csh logout used at logout time
(csh(1))
SEE ALSO
csh(1), ksh(1), mail(1), newgrp(1), sh(1), su(1), passwd(4),
profile(4), environ(5).
DIAGNOSTICS
Login incorrect
If the user name or the password cannot be matched.
No shell, cannot open password file, or no directory
Consult a system administrator.
No utmp entry. You must exec login from the lowest level sh.
If you attempted to execute login as a command without
using the shell's exec internal command or from other
than the login shell. (Applies only to Bourne shell,
sh(1).)
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