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login(1) [bsd man page]

LOGIN(1)						      General Commands Manual							  LOGIN(1)

NAME
login - sign on SYNOPSIS
login [ -p ] [ username ] DESCRIPTION
The login command is used when a user initially signs on, or it may be used at any time to change from one user to another. The latter case is the one summarized above and described here. See "How to Get Started" for how to dial up initially. If login is invoked without an argument, it asks for a user name, and, if appropriate, a password. Echoing is turned off (if possible) during the typing of the password, so it will not appear on the written record of the session. After a successful login, accounting files are updated and the user is informed of the existence of mail. The message of the day is printed, as is the time of his last login. Both are suppressed if he has a ".hushlogin" file in his home directory; this is mostly used to make life easier for non-human users, such as uucp. Login initializes the user and group IDs and the working directory, then executes a command interpreter (usually csh(1)) according to spec- ifications found in a password file. Argument 0 of the command interpreter is the name of the command interpreter with a leading dash ("-"). Login also modifies the environment environ(7) with information specifying home directory, command interpreter, terminal type (if avail- able) and user name. The `-p' argument causes the remainder of the environment to be preserved, otherwise any previous environment is dis- carded. If the file /etc/nologin exists, login prints its contents on the user's terminal and exits. This is used by shutdown(8) to stop users log- ging in when the system is about to go down. Login is recognized by sh(1) and csh(1) and executed directly (without forking). FILES
/var/run/utmp accounting /usr/adm/wtmp accounting /usr/spool/mail/* mail /etc/motd message-of-the-day /etc/passwd password file /etc/nologin stops logins .hushlogin makes login quieter SEE ALSO
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), shutdown(8), rlogin(1c) DIAGNOSTICS
"Login incorrect," if the name or the password is bad. "No Shell", "cannot open password file", "no directory": consult a programming counselor. BUGS
An undocumented option, -r is used by the remote login server, rlogind(8C) to force login to enter into an initial connection protocol. -h is used by telnetd(8C) and other servers to list the host from which the connection was received. 4th Berkeley Distribution November 27, 1996 LOGIN(1)

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LOGIN(1)						   Linux Administrator's Manual 						  LOGIN(1)

NAME
login - Begin session on the system SYNOPSIS
login [ -p ] [ -h host ] [ -H ] [ -f username | username ] DESCRIPTION
login is used when signing onto a system. If no argument is given, login prompts for the username. The user is then prompted for a password, where approprate. Echoing is disabled to prevent revealing the password. Only a small number of password failures are permitted before login exits and the communications link is severed. If password aging has been enabled for the account, the user may be prompted for a new password before proceeding. He will be forced to provide his old password and the new password before continuing. Please refer to passwd(1) for more information. The user and group ID will be set according to their values in the file. There is one exception if the user ID is zero: in this case, only the primary group ID of the account is set. This should prevent that the system adminitrator cannot login in case of network problems. The value for $HOME, $SHELL, $PATH, $LOGNAME, and $MAIL are set according to the appropriate fields in the password entry. $PATH defaults to /usr/local/bin:/bin:/usr/bin:. for normal users, and to /sbin:/bin:/usr/sbin:/usr/bin for root if not other configured. The environment variable $TERM will be preserved, if it exists (other environment variables are preserved if the -p option is given) or be initialize to the terminal type on your tty line, as specified in /etc/ttytype. Then the user's shell is started. If no shell is specified for the user in /etc/passwd, then /bin/sh is used. If there is no directory specified in /etc/passwd, then / is used (the home directory is checked for the .hushlogin file described above). login reads the /etc/login.defs(5) configuration file. Please refer to this documenation for options which could be set. OPTIONS
-p Used by getty(8) to tell login not to destroy the environment -f Used to skip a second login authentication. This option is deprecated and should not be used. It does specifically not work for root. Using this option also means, that not all PAM functions are called. -h Used by other servers (i.e., telnetd(8)) to pass the name of the remote host to login so that it may be placed in utmp and wtmp. Only the superuser may use this option. -H Used by other servers (i.e., telnetd(8)) to tell login that printing the hostname should be suppressed in the login: prompt. FILES
/var/run/utmp - list of current login sessins /var/log/wtmp - list of previous login sessions /etc/passwd - user account information /etc/shadow - encrypted passwords and age information /etc/motd - system message file /etc/login.defs - configuration file SEE ALSO
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), shutdown(8), login.defs(5) BUGS
A recursive login, as used to be possible in the good old days, no longer works; for most purposes su(1) is a satisfactory substitute. Indeed, for security reasons, login does a vhangup() system call to remove any possible listening processes on the tty. This is to avoid password sniffing. If one uses the command "login", then the surrounding shell gets killed by vhangup() because it's no longer the true owner of the tty. This can be avoided by using "exec login" in a top-level shell or xterm. AUTHOR
Derived from BSD login 5.40 (5/9/89) by Michael Glad (glad@daimi.dk) for HP-UX Ported to Linux 0.12: Peter Orbaek (poe@daimi.aau.dk) Added new features: Thorsten Kukuk (kukuk@suse.de) PAM Login 3.32 2. May 2007 LOGIN(1)
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