Man Login en anglais
LOGIN(1) User Commands LOGIN(1)
NAME
login - begin session on the system
SYNOPSIS
login [-p] [username] [ENV=VAR...]
login [-p] [-h host] [-f username]
login [-p] -r host
DESCRIPTION
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. Typically, login is treated by the shell
as exec login which causes the user to exit from the current shell.
Attempting to execute login from any shell but the login shell will
produce an error message.
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 your account, you may be
prompted for a new password before proceeding. You will be forced to
provide your old password and the new password before continuing.
Please refer to passwd(1) for more information.
After a successful login, you will be informed of any system messages
and the presence of mail. You may turn off the printing of the system
message file, /etc/motd, by creating a zero-length file .hushlogin in
your login directory. The mail message will be one of "You have new
mail.", "You have mail.", or "No Mail." according to the condition of
your mailbox.
Your user and group ID will be set according to their values in the
/etc/passwd file. The value for $HOME, $SHELL, $PATH, $LOGNAME, and
$MAIL are set according to the appropriate fields in the password
entry. Ulimit, umask and nice values may also be set according to
entries in the GECOS field.
On some installations, the environmental variable $TERM will be
initialized to the terminal type on your tty line, as specified in
/etc/ttytype.
An initialization script for your command interpreter may also be
executed. Please see the appropriate manual section for more
information on this function.
A subsystem login is indicated by the presence of a "*" as the first
character of the login shell. The given home directory will be used as
the root of a new file system which the user is actually logged into.
The login program is NOT responsible for removing users from the utmp
file. It is the responsibility of getty(8) and init(8) to clean up
apparent ownership of a terminal session. If you use login from the
shell prompt without exec, the user you use will continue to appear to
be logged in even after you log out of the "subsession".
OPTIONS
-f
Do not perform authentication, user is preauthenticated.
-h
Name of the remote host for this login.
-p
Preserve environment.
-r
Perform autologin protocol for rlogin.
The -r, -h and -f options are only used when login is invoked by root.
CAVEATS
This 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 clean up
apparent ownership of a terminal session. If you use login from the
shell prompt without exec, the user you use will continue to appear 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 use this to
obtain the password of the next person coming to sit in front of the
machine. Under Linux, the SAK mechanism can be used by users to
initiate a trusted path and prevent this kind of attack.
CONFIGURATION
The 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 group set when
logging in on the console (as determined by the CONSOLE setting).
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 in 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 can be preceded by PATH=, or a
colon separated list of paths (for example /bin:/usr/bin). 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 can be preceded by PATH=, or a
colon separated list of paths (for example
/sbin:/bin:/usr/sbin:/usr/bin). The default value is
PATH=/bin:/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 hushed mode
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 enabled if 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 overriden by PAM, since the default
pam_unix module has it's own built in of 3 retries. However, this
is a 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 number and
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 "vt100 tty01".
USERGROUPS_ENAB (boolean)
FILES
/var/run/utmp
List of current login sessions.
/var/log/wtmp
List of previous login sessions.
/etc/passwd
User account information.
/etc/shadow
Secure user account information.
/etc/motd
System message of the day file.
/etc/nologin
Prevent non-root users from logging in.
/etc/ttytype
List of terminal types.
$HOME/.hushlogin
Suppress printing of system messages.
SEE ALSO
mail(1), passwd(1), sh(1), su(1), login.defs(5), nologin(5), passwd(5),
securetty(5), getty(8).
User Commands 12/06/2009 LOGIN(1)
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