Linux "login" Command Line Options and Examples
write utmp and wtmp entries
The login program is used to establish a new session with the system. It is normally invoked automatically by responding to the login: prompt on the user's terminal. login may be special to the shell and may not be invoked as a sub-process.
login [-p] [-h host] [username] [ENV=VAR...]
login [-p] [-h host] -f username
login [-p] -r host
Command Line Options:
Do not perform authentication, user is preauthenticated.Note: In that case, username is mandatory.
login -f ...
Name of the remote host for this login.
login -h ...
login -p ...
Perform autologin protocol for rlogin.The -r, -h and -f options are only used when login is invoked by root.CAVEATSThis version of login has many compilation options, only some of which may be in use at any particular site.The location of files is subject to differences in system configuration.The login program is NOT responsible for removing users from the utmp file. It is the responsibility of getty(8) and init(8) to cleanup apparent ownership of a terminal session. If you use login from the shell prompt without exec, the user you use will continue toappear to be logged in even after you log out of the "subsession".As with any program, login's appearance can be faked. If non-trusted users have physical access to a machine, an attacker could usethis to obtain the password of the next person coming to sit in front of the machine. Under Linux, the SAK mechanism can be used byusers to initiate a trusted path and prevent this kind of attack.CONFIGURATIONThe following configuration variables in /etc/login.defs change the behavior of this tool:CONSOLE_GROUPS (string)List of groups to add to the user's supplementary groups set when logging in on the console (as determined by the CONSOLEsetting). Default is none.Use with caution - it is possible for users to gain permanent access to these groups, even when not logged in on the console.DEFAULT_HOME (boolean)Indicate if login is allowed if we can't cd to the home directory. Default is no.If set to yes, the user will login in the root (/) directory if it is not possible to cd to her home directory.ENV_PATH (string)If set, it will be used to define the PATH environment variable when a regular user login. The value is a colon separated list ofpaths (for example /bin:/usr/bin) and can be preceded by PATH=. The default value is PATH=/bin:/usr/bin.ENV_SUPATH (string)If set, it will be used to define the PATH environment variable when the superuser login. The value is a colon separated list ofpaths (for example /sbin:/bin:/usr/sbin:/usr/bin) and can be preceded by PATH=. The default value isPATH=/sbin:/bin:/usr/sbin:/usr/bin.ERASECHAR (number)Terminal ERASE character (010 = backspace, 0177 = DEL).The value can be prefixed "0" for an octal value, or "0x" for an hexadecimal value.FAIL_DELAY (number)Delay in seconds before being allowed another attempt after a login failure.FAKE_SHELL (string)If set, login will execute this shell instead of the users' shell specified in /etc/passwd.HUSHLOGIN_FILE (string)If defined, this file can inhibit all the usual chatter during the login sequence. If a full pathname is specified, then hushedmode will be enabled if the user's name or shell are found in the file. If not a full pathname, then hushed mode will be enabledif the file exists in the user's home directory.KILLCHAR (number)Terminal KILL character (025 = CTRL/U).The value can be prefixed "0" for an octal value, or "0x" for an hexadecimal value.LOGIN_RETRIES (number)Maximum number of login retries in case of bad password.This will most likely be overridden by PAM, since the default pam_unix module has its own built in of 3 retries. However, this isa safe fallback in case you are using an authentication module that does not enforce PAM_MAXTRIES.LOGIN_TIMEOUT (number)Max time in seconds for login.LOG_OK_LOGINS (boolean)Enable logging of successful logins.LOG_UNKFAIL_ENAB (boolean)Enable display of unknown usernames when login failures are recorded.Note: logging unknown usernames may be a security issue if an user enter her password instead of her login name.TTYGROUP (string), TTYPERM (string)The terminal permissions: the login tty will be owned by the TTYGROUP group, and the permissions will be set to TTYPERM.By default, the ownership of the terminal is set to the user's primary group and the permissions are set to 0600.TTYGROUP can be either the name of a group or a numeric group identifier.If you have a write program which is "setgid" to a special group which owns the terminals, define TTYGROUP to the group numberand TTYPERM to 0620. Otherwise leave TTYGROUP commented out and assign TTYPERM to either 622 or 600.TTYTYPE_FILE (string)If defined, file which maps tty line to TERM environment parameter. Each line of the file is in a format something like "vt100tty01".USERGROUPS_ENAB (boolean)If set to yes, userdel will remove the user's group if it contains no more members, and useradd will create by default a groupwith the name of the user.FILES/var/run/utmpList of current login sessions./var/log/wtmpList of previous login sessions./etc/passwdUser account information./etc/shadowSecure user account information./etc/motdSystem message of the day file./etc/nologinPrevent non-root users from logging in./etc/ttytypeList of terminal types.$HOME/.hushloginSuppress printing of system messages./etc/login.defsShadow password suite configuration.
login -r ...