The user is then prompted for a password, where appropriate. 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 administrator 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 otherwise configured.
The environment variable $TERM will be preserved, if it exists (other environment variables are preserved if the -p option is given), else it will be initialized 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).
- Used by getty(8) to tell login not to destroy the environment.
- Used to skip a second login authentication. This specifically does not work for root, and does not appear to work well under Linux.
- 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 proper PAM config files (e.g. /etc/pam.d/login and /etc/pam.d/remote).
- Used by other servers (i.e., telnetd(8)) to tell login that printing the hostname should be suppressed in the login: prompt. See also LOGIN_PLAIN_PROMPT below if your server does not allow to configure login command line.
- Display help text and exit.
- -V, --version
- Display version information and exit.
The TTYGROUP can be either the name of a group or a numeric group identifier.
If a full pathname is not 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 it does not exist then ~/.hushlogin
If the HUSHLOGIN_FILE item is empty, then all the checks are disabled.
Note that logging unknown usernames may be a security issue if a user enters her password instead of her login name.
/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
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.
Ported to Linux 0.12: Peter Orbaek
Rewritten to a PAM-only version by Karel Zak