LOGIN(1) User Commands LOGIN(1)


NAME


login - sign on to the system

SYNOPSIS


login [-p] [-d device] [-R repository] [-s service]
[-t terminal] [-u identity] [-U ruser]
[-h hostname [terminal] | -r hostname]
[name [environ]...]


DESCRIPTION


The login command is used at the beginning of each terminal session to
identify oneself to the system. login is invoked by the system when a
connection is first established, after the previous user has terminated
the login shell by issuing the exit command.


If login is invoked as a command, it must replace the initial command
interpreter. To invoke login in this fashion, type:

exec login


from the initial shell. The C shell and Korn shell have their own built-
ins of login. See ksh(1), ksh93(1), and csh(1) for descriptions of login
built-ins and usage.


login asks for your user name, if it is not supplied as an argument, and
your password, if appropriate. Where possible, echoing is turned off
while you type your password, so it does not appear on the written record
of the session.


If you make any mistake in the login procedure, the message:

Login incorrect


is printed and a new login prompt appears. If you make five incorrect
login attempts, all five can be logged in /var/adm/loginlog, if it
exists. The TTY line is dropped.


If password aging is turned on and the password has aged (see passwd(1)
for more information), the user is forced to changed the password. In
this case the /etc/nsswitch.conf file is consulted to determine password
repositories. See nsswitch.conf(4) for a list of valid nameservice
configurations that are permitted for the passwd: database if password
aging is enabled.


Failure to comply with the configurations prevents the user from logging
onto the system because passwd(1) fails. If you do not complete the login
successfully within a certain period of time, it is likely that you are
silently disconnected.


After a successful login, accounting files are updated. Device owner,
group, and permissions are set according to the contents of the
/etc/logindevperm file, and the time you last logged in is printed (see
logindevperm(4)).


The user-ID, group-ID, supplementary group list, and working directory
are initialized, and the command interpreter (usually ksh) is started.


The basic environment is initialized to:

HOME=your-login-directory
LOGNAME=your-login-name
PATH=/usr/bin:
SHELL=last-field-of-passwd-entry
MAIL=/var/mail/
TZ=timezone-specification


For Bourne shell and Korn shell logins, the shell executes /etc/profile
and $HOME/.profile, if it exists.


For the ksh93 Korn shell, an interactive shell then executes
/etc/ksh.kshrc, followed by the file specified by the ENV environment
variable. If $ENV is not set, this defaults to $HOME/.kshrc. For the ksh
and /usr/xpg4/bin/sh Korn Shell, an interactive shell executes the file
named by $ENV (no default).


For C shell logins, the shell executes /etc/.login, $HOME/.cshrc, and
$HOME/.login. The default /etc/profile and /etc/.login files check quotas
(see quota(1M)), print /etc/motd, and check for mail. None of the
messages are printed if the file $HOME/.hushlogin exists. The name of the
command interpreter is set to - (dash), followed by the last component of
the interpreter's path name, for example, -sh.


If the login-shell field in the password file (see passwd(4)) is empty,
then the default command interpreter, /usr/bin/sh, is used. If this field
is * (asterisk), then the named directory becomes the root directory. At
that point, login is re-executed at the new level, which must have its
own root structure.


The environment can be expanded or modified by supplying additional
arguments to login, either at execution time or when login requests your
login name. The arguments can take either the form xxx or xxx=yyy.
Arguments without an = (equal sign) are placed in the environment as:

Ln=xxx


where n is a number starting at 0 and is incremented each time a new
variable name is required. Variables containing an = (equal sign) are
placed in the environment without modification. If they already appear in
the environment, then they replace the older values.


There are two exceptions: The variables PATH and SHELL cannot be changed.
This prevents people logged into restricted shell environments from
spawning secondary shells that are not restricted. login understands
simple single-character quoting conventions. Typing a \ (backslash) in
front of a character quotes it and allows the inclusion of such
characters as spaces and tabs.


Alternatively, you can pass the current environment by supplying the -p
flag to login. This flag indicates that all currently defined environment
variables should be passed, if possible, to the new environment. This
option does not bypass any environment variable restrictions mentioned
above. Environment variables specified on the login line take
precedence, if a variable is passed by both methods.


To enable remote logins by root, edit the /etc/default/login file by
inserting a # (pound sign) before the CONSOLE=/dev/console entry. See
FILES.

SECURITY


For accounts in name services which support automatic account locking,
the account can be configured to be automatically locked (see
user_attr(4) and policy.conf(4)) if successive failed login attempts
equals or exceeds RETRIES. Currently, only the files repository (see
passwd(4) and shadow(4)) supports automatic account locking. See also
pam_unix_auth(5).


The login command uses pam(3PAM) for authentication, account management,
session management, and password management. The PAM configuration
policy, listed through /etc/pam.conf, specifies the modules to be used
for login. Here is a partial pam.conf file with entries for the login
command using the UNIX authentication, account management, and session
management modules:

login auth required pam_authtok_get.so.1
login auth required pam_dhkeys.so.1
login auth required pam_unix_auth.so.1
login auth required pam_dial_auth.so.1

login account requisite pam_roles.so.1
login account required pam_unix_account.so.1

login session required pam_unix_session.so.1


The Password Management stack looks like the following:

other password required pam_dhkeys.so.1
other password requisite pam_authtok_get.so.1
other password requisite pam_authtok_check.so.1
other password required pam_authtok_store.so.1


If there are no entries for the service, then the entries for the other
service is used. If multiple authentication modules are listed, then the
user can be prompted for multiple passwords.


When login is invoked through rlogind or telnetd, the service name used
by PAM is rlogin or telnet, respectively.

OPTIONS


The following options are supported:

-d device
login accepts a device option, device. device
is taken to be the path name of the TTY port
login is to operate on. The use of the device
option can be expected to improve login
performance, since login does not need to call
ttyname(3C). The -d option is available only to
users whose UID and effective UID are root. Any
other attempt to use -d causes login to quietly
exit.


-h hostname [terminal]
Used by in.telnetd(1M) to pass information
about the remote host and terminal type.

Terminal type as a second argument to the -h
option should not start with a hyphen (-).


-p
Used to pass environment variables to the login
shell.


-r hostname
Used by in.rlogind(1M) to pass information
about the remote host.


-R repository
Used to specify the PAM repository that should
be used to tell PAM about the "identity" (see
option -u below). If no "identity" information
is passed, the repository is not used.


-s service
Indicates the PAM service name that should be
used. Normally, this argument is not necessary
and is used only for specifying alternative PAM
service names. For example: "ktelnet" for the
Kerberized telnet process.


-u identity
Specifies the "identity" string associated with
the user who is being authenticated. This
usually is not be the same as that user's Unix
login name. For Kerberized login sessions, this
is the Kerberos principal name associated with
the user.


-U ruser
Indicates the name of the person attempting to
login on the remote side of the rlogin
connection. When in.rlogind(1M) is operating in
Kerberized mode, that daemon processes the
terminal and remote user name information prior
to invoking login, so the "ruser" data is
indicated using this command line parameter.
Normally (non-Kerberos authenticated rlogin),
the login daemon reads the remote user
information from the client.


EXIT STATUS


The following exit values are returned:

0
Successful operation.


non-zero
Error.


FILES


$HOME/.cshrc
Initial commands for each csh.


$HOME/.hushlogin
Suppresses login messages.


$HOME/.kshrc
User's commands for interactive ksh93, if $ENV is
unset; executes after /etc/ksh.kshrc.


$HOME/.login
User's login commands for csh.


$HOME/.profile
User's login commands for sh, ksh, and ksh93.


$HOME/.rhosts
Private list of trusted hostname/username
combinations.


/etc/.login
System-wide csh login commands.


/etc/issue
Issue or project identification.


/etc/ksh.kshrc
System-wide commands for interactive ksh93.


/etc/logindevperm
Login-based device permissions.


/etc/motd
Message-of-the-day.


/etc/nologin
Message displayed to users attempting to login
during machine shutdown.


/etc/passwd
Password file.


/etc/profile
System-wide sh, ksh, and ksh93 login commands.


/etc/shadow
List of users' encrypted passwords.


/usr/bin/sh
User's default command interpreter.


/var/adm/lastlog
Time of last login.


/var/adm/loginlog
Record of failed login attempts.


/var/adm/utmpx
Accounting.


/var/adm/wtmpx
Accounting.


/var/mail/your-name
Mailbox for user your-name.


/etc/default/login
Default value can be set for the following flags
in /etc/default/login. Default values are
specified as comments in the /etc/default/login
file, for example, TIMEZONE=EST5EDT.

TIMEZONE
Sets the TZ environment
variable of the shell (see
environ(5)).


HZ
Sets the HZ environment
variable of the shell.


ULIMIT
Sets the file size limit
for the login. Units are
disk blocks. Default is
zero (no limit).


CONSOLE
If set, root can login on
that device only. This
does not prevent execution
of remote commands with
rsh(1). Comment out this
line to allow login by
root.


PASSREQ
Determines if login
requires a non-null
password.


ALTSHELL
Determines if login should
set the SHELL environment
variable.


PATH
Sets the initial shell
PATH variable.


SUPATH
Sets the initial shell
PATH variable for root.


TIMEOUT
Sets the number of seconds
(between 0 and 900) to
wait before abandoning a
login session.


UMASK
Sets the initial shell
file creation mode mask.
See umask(1).


SYSLOG
Determines whether the
syslog(3C) LOG_AUTH
facility should be used to
log all root logins at
level LOG_NOTICE and
multiple failed login
attempts atLOG_CRIT.


DISABLETIME
If present, and greater
than zero, the number of
seconds that login waits
after RETRIES failed
attempts or the PAM
framework returns
PAM_ABORT. Default is 20
seconds. Minimum is 0
seconds. No maximum is
imposed.


SLEEPTIME
If present, sets the
number of seconds to wait
before the login failure
message is printed to the
screen. This is for any
login failure other than
PAM_ABORT. Another login
attempt is allowed,
providing RETRIES has not
been reached or the PAM
framework is returned
PAM_MAXTRIES. Default is
4 seconds. Minimum is 0
seconds. Maximum is 5
seconds.

Both su(1M) and
sulogin(1M) are affected
by the value of SLEEPTIME.


RETRIES
Sets the number of retries
for logging in (see
pam(3PAM)). The default is
5. The maximum number of
retries is 15. For
accounts configured with
automatic locking (see
SECURITY above), the
account is locked and
login exits. If automatic
locking has not been
configured, login exits
without locking the
account.


SYSLOG_FAILED_LOGINS
Used to determine how many
failed login attempts are
allowed by the system
before a failed login
message is logged, using
the syslog(3C) LOG_NOTICE
facility. For example, if
the variable is set to 0,
login logs all failed
login attempts.


ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Committed |
+--------------------+-----------------+

SEE ALSO


csh(1), exit(1), ksh(1), ksh93(1), mail(1), mailx(1), newgrp(1),
passwd(1), rlogin(1), rsh(1), sh(1), shell_builtins(1), telnet(1),
umask(1), in.rlogind(1M), in.telnetd(1M), logins(1M), quota(1M), su(1M),
sulogin(1M), syslogd(1M), useradd(1M), userdel(1M), pam(3PAM),
rcmd(3SOCKET), syslog(3C), ttyname(3C), auth_attr(4), exec_attr(4),
hosts.equiv(4), issue(4), logindevperm(4), loginlog(4), nologin(4),
nsswitch.conf(4), pam.conf(4), passwd(4), policy.conf(4), profile(4),
shadow(4), user_attr(4), utmpx(4), wtmpx(4), attributes(5), environ(5),
pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5),
pam_authtok_check(5), pam_authtok_get(5), pam_authtok_store(5),
pam_dhkeys(5), pam_passwd_auth(5), termio(7I)

DIAGNOSTICS


Login incorrect

The user name or the password cannot be matched.


Not on system console

Root login denied. Check the CONSOLE setting in /etc/default/login.


No directory! Logging in with home=/

The user's home directory named in the passwd(4) database cannot be
found or has the wrong permissions. Contact your system
administrator.


No shell

Cannot execute the shell named in the passwd(4) database. Contact
your system administrator.


NO LOGINS: System going down in N minutes

The machine is in the process of being shut down and logins have been
disabled.


WARNINGS


Users with a UID greater than 76695844 are not subject to password aging,
and the system does not record their last login time.


If you use the CONSOLE setting to disable root logins, you should arrange
that remote command execution by root is also disabled. See rsh(1),
rcmd(3SOCKET), and hosts.equiv(4) for further details.

NOTES


The pam_unix(5) module is no longer supported. Similar functionality is
provided by pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5),
pam_authtok_check(5), pam_authtok_get(5), pam_authtok_store(5),
pam_dhkeys(5), and pam_passwd_auth(5).


February 25, 2017 LOGIN(1)