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)
Check Out this Related Man Page
LOGIN(1) User Commands 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 /etc/passwd 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 allow the system adminitrator to login even in case of network problems. The value for $HOME, $USER, $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 /usr/local/sbin:/usr/local/bin:/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. 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 below). If the file .hushlogin exists, then a "quiet" login is performed (this disables the checking of mail and the printing of the last login time and message of the day). Otherwise, if /var/log/lastlog exists, the last login time is printed (and the current login is recorded). OPTIONS
-p Used by getty(8) to tell login not to destroy the environment. -f Used to skip a second login authentication. This specifically does not work for root, and does not appear to work well under Linux. -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. Note that the -h option has impact on the PAM service name. The standard service name is login, with the -h option the name is remote. It is necessary to create a proper PAM config files (e.g. /etc/pam.d/login and /etc/pam.d/remote). -H Used by other servers (i.e., telnetd(8)) to tell login that printing the hostname should be suppressed in the login: prompt. -V Print version and exit. CONFIG FILE ITEMS
login reads the /etc/login.defs(5) configuration file. Note that the configuration file could be distributed with another package (e.g. shadow-utils). The following configuration items are relevant for login(1): MOTD_FILE (string) If defined, ":" delimited list of "message of the day" files to be displayed upon login. The default value is /etc/motd. If the MOTD_FILE item is empty or quiet login is enabled then the message of the day is not displayed. Note that the same functionality is also provided by pam_motd(8) PAM module. LOGIN_TIMEOUT (number) Max time in seconds for login. The default value is 60. LOGIN_RETRIES (number) Maximum number of login retries in case of bad password. The default value is 3. FAIL_DELAY (number) Delay in seconds before being allowed another three tries after a login failure. The default value is 5. TTYPERM (string) The terminal permissions. The default value is 0600 or 0620 if tty group is used. TTYGROUP (string) The login tty will be owned by the TTYGROUP. The default value is tty. If the TTYGROUP does not exist then the ownership of the ter- minal is set to the user's primary group. The TTYGROUP can be either the name of a group or a numeric group identifier. HUSHLOGIN_FILE (string) If defined, this file can inhibit all the usual chatter during the login sequence. If a full pathname (e.g. /etc/hushlogins) is spec- ified, then hushed mode will be enabled if the user's name or shell are found in the file. If this global hush login file is empty then the hushed mode will be enabled for all users. If not a full pathname is specified, then hushed mode will be enabled if the file exists in the user's home directory. The default is to check /etc/hushlogins and if does not exist then ~/.hushlogin If the HUSHLOGIN_FILE item is empty then all checks are disabled. DEFAULT_HOME (boolean) Indicate if login is allowed if we can not change directory to the home directory. If set to yes, the user will login in the root (/) directory if it is not possible to change directory to her home. The default value is yes. LOG_UNKFAIL_ENAB (boolean) Enable display of unknown usernames when login failures are recorded. The default value is no. Note that logging unknown usernames may be a security issue if an user enter her password instead of her login name. ENV_PATH (string) If set, it will be used to define the PATH environment variable when a regular user login. The default value is /usr/local/bin:/bin: /usr/bin ENV_ROOTPATH (string) ENV_SUPATH (string) If set, it will be used to define the PATH environment variable when the superuser login. The default value is /usr/local/sbin:/usr /local/bin:/sbin:/bin:/usr/sbin:/usr/bin FILES
/var/run/utmp /var/log/wtmp /var/log/lastlog /var/spool/mail/* /etc/motd /etc/passwd /etc/nologin /etc/pam.d/login /etc/pam.d/remote /etc/hushlogins .hushlogin SEE ALSO
init(8), getty(8), mail(1), passwd(1), passwd(5), environ(7), shutdown(8) BUGS
The undocumented BSD -r option is not supported. This may be required by some rlogind(8) programs. 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> Rewritten to PAM-only version by Karel Zak <kzak@redhat.com> AVAILABILITY
The login command is part of the util-linux package and is available from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util- linux/>. util-linux June 2012 LOGIN(1)