LOGIN(M) XENIX System V LOGIN(M)
Name
login - Gives access to the system.
Description
The login command is used at the beginning of each terminal
session and allows you to identify yourself to the system.
It cannot be invoked except when a connection is first
established, or after the previous user has logged out by
sending an end-of-file ( Ctrl-D ) to his initial shell.
login prompts for your user name, and if appropriate, your
password. Echoing is turned off (where possible) while
entering your password, so it will not appear on the written
record of the session.
If password aging has been invoked by the superuser on your
behalf, your password may have expired. In this case, you
will be shunted into passwd(C) to change it, after which you
may attempt to log in again.
If you do not complete the login successfully within a
certain period of time (e.g., one minute), you are likely to
be returned to the ``login:'' prompt or silently
disconnected from a dial-up line.
After a successful login, accounting files (/etc/utmp and
/etc/wtmp) are updated, you are told if you have any mail,
and the start-up profile files (i.e., /etc/profile and
$HOME/.profile), if any, are executed. See profile(M).
login checks /etc/default/login for ULIMIT (maximum file
size in 512 byte blocks, default is 2,097,152), and for
environment variables, such as TZ (time zone), HZ (hertz),
and ALTSHELL (allows other than sh shell types). Other
entries sometimes found in /etc/default/login are IDLEWEEKS,
CONSOLE, and PASSREQ. IDLEWEEKS=n, where n is a number of
weeks, works in conjunction with pwadmin(C). If a password
has expired, you are prompted to choose a new one. If it
has expired beyond IDLEWEEKS, the user is not allowed to log
in, and must consult system administrator. The
CONSOLE=/dev/??? entry means that root can only log in on
the /dev listed. PASSREQ=YES, if set, forces you to select a
password if you do not have one.
login initializes the user and group IDs and the working
directory, then executes a command interpreter (usually
sh(C)) according to specifications found in the /etc/passwd
file. Argument 0 of the command interpreter is a dash (-)
followed by the last component
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LOGIN(M) XENIX System V LOGIN(M)
of the interpreter's pathname. The environment (see
environ(M)) is initialized to:
HOME= your-login-directory
PATH=:/bin:/usr/bin
Initially, umask is set to octal 022 by login.
Files
/etc/utmp Information on current logins
/etc/wtmp History of logins since last
multiuser
/usr/spool/mail/your-name Mailbox for user your-name
/etc/motd Message of the day
/etc/default/login Default values for environment
variables
/etc/passwd Password file
/etc/profile System profile
$HOME/.profile Personal profile
See Also
environ(M), getty(M), machine(M), mail(C), newgrp(C),
passwd(C), passwd(M), profile(M), su(C), sh(C), ulimit(S),
umask(C), who(C).
Diagnostics
Login incorrect
The user name or the password is incorrect.
No shell, cannot open password file, no directory:
Your account has not been properly set up.
Your password has expired. Choose a new one.
Password aging is implemented and yours has expired.
Notes
Under System V, only the superuser may execute login from a
shell. Hence, non-superusers must log out in order to log
in as another user. Pre-system III login, if invoked from
the command line while someone is logged on already, logs
the current user out and logs in the new user. The current
login nests, i.e., the current user is not logged out.
Thus, it is somewhat like su(C), except that the new user's
.login or .profile is run. Permissions and environment are
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those of the new user. When the new user logs out, the
previous user is still running. This practice is not
recommended, as nested logins can impair system performance.
As explained in machine(M), when setting ULIMIT in the
/etc/default/login file on filesystems with 1024 byte blocks
(see machine(M)), be sure to specify even numbers, as the
ULIMIT variable accepts a number of 512-byte blocks. The
default is 2,097,152 blocks, or 1 gigabyte. Use this
variable to increase or decrease the maximum allowable file
size.
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