LOGIN(5)

NAME
/etc/login.defs - Login configuration

DESCRIPTION
The /etc/login.defs file defines the site-specific configuration for the shadow login suite. This file is required. Absence of this file will not prevent system operation, but will probably result in undesirable operation.

This file is a readable text file, each line of the file describing one configuration parameter. The lines consist of a configuration name and value, seperated by whitespace. Blank lines and comment lines are ignored. Comments are introduced with a `#' pound sign and the pound sign must be the first non-white character of the line.

Parameter values may be of four types: strings, booleans, numbers, and long numbers. A string is comprised of any printable characters. A boolean should be either the value ``yes'' or ``no''. An undefined boolean parameter or one with a value other than these will be given a ``no'' value. Numbers (both regular and long) may be either decimal values, octal values (precede the value with ``0'') or hexadecimal values (precede the value with ``0x''). The maximum value of the regular and long numeric parameters is machine-dependant.

The following configuration items are provided:

CONSOLE (string)
    If specified, this definition provides for a restricted set of lines on which root logins will be allowed. An attempted root login which does not meet the criteria established here will be rejected. The value of this field may be one of two forms, either a fully-rooted pathname such as

        CONSOLE /etc/consoles

    or a colon-delimited list of terminal lines such as:

        CONSOLE console:tty01:tty02:tty03:tty04

    If a pathname is given, each line of the file should specify one terminal line. If this parameter is not defined or the specified file does not exist, then root logins will be allowed from any terminal line. Because the removal of this file, or its truncation, could result in unauthorized root logins, this file must be protected. Where security is critical, the colon-separated form should be used to prevent this potential method of attack.

DIALUPS_CHECK_ENAB (boolean)
    If yes and an /etc/dialups file exists, then secondary passwords are enabled upon the dialup lines specified in this file. This file should contain a list of dialups, one per line, for example:

    	ttyfm01
    	ttyfm02
    	  .
    	  .
    	  .

ENV_HZ (string)
    This parameter specifies a value for an HZ environment parameter. Example usage is:

        ENV_HZ HZ=50

    If this parameter is not defined then no HZ value will be established.

ENV_PATH (string)
    This parameter must be defined as the search path for regular users. When a login with UID other than zero occurs, the PATH environment parameter is initialized to this value. This parameter is required; if undefined a possibly incorrect default value will be provided.

ENV_SUPATH (string)
    This parameter must be defined as the search path for the superuser. When a login with UID zero occurs, the PATH environment parameter is initialized to this value. This parameter is required; if undefined a possibly incorrect default value will be provided.

ENV_TZ (string)
    This parameter specifies information for generating a TZ environment parameter. The value must either be the desired contents of TZ, or the full pathname of a file which contains this information. Example usage is:

        ENV_TZ TZ=CST6CDT

    or

        ENV_TZ /etc/tzname

    If a nonexistent file is named, then TZ will be initialized to some default value. If this parameter is not defined then no TZ value will be established.

ERASECHAR (number)
    The terminal erase character is initialized to this value. This is supported only on systems with the termio interface, e.g. System V. If not specified, the erase character will be initialized to a backspace. See KILLCHAR for related information.

FAILLOG_ENAB (boolean)
    If yes then login failures will be accumulated in /usr/adm/faillog in a faillog(8) format.

FTMP_FILE (string)
    This parameter specifies the full pathname to a file to which login failures are recorded. When a login failure occurs, a utmp format record will be appended to this file. Note that this differs from the /usr/adm/faillog failure logging in that this facility logs every failure whereas the ``faillog'' facility accumulates failure information per user. If this parameter is not specified then logging will be inhibited. See FAILLOG_ENAB and LOG_UNKFAIL_ENAB for related information.

HUSHLOGIN_FILE (string)
    This parameter is used to establish ``hushlogin'' conditions. There are two possible ways to establish these conditions. First, if the value of this parameter is a filename and that file exists in the user's home directory then ``hushlogin'' conditions will be in effect. The contents of this file are ignored; its mere presence triggers ``hushlogin'' conditions. Second, if the value of this parameter is a full pathname and either the user's login name or the user's shell is found in this file, then ``hushlogin'' conditions will be in effect. In this case, the file should be in a format similar to:

    	demo
    	/usr/lib/uucp/uucico
    	  .
    	  .
    	  .

    If this parameter is not defined, then ``hushlogin'' conditions will never occur. When ``hushlogin'' conditions are established, the message of the day, last successful and unsuccessful login display, mail status display, and password aging checks are suppressed. Note that allowing hushlogin files in user home directories allows the user to disable password aging checks. See MOTD_FILE, FAILLOG_ENAB, LASTLOG_ENAB, and MAIL_CHECK_ENAB for related information.

KILLCHAR (number)
    The terminal kill character is initialized to this value. This is supported only on systems with the termio interface, e.g. System V. If not specified, the kill character will be initialized to a CTRL/U. See ERASECHAR for related information.

LASTLOG_ENAB (boolean)
    If yes, and if the /usr/adm/lastlog file exists, then a successful user login will be recorded to this file. Furthermore, if this option is enabled then the times of the most recent successful and unsuccessful logins will be displayed to the user upon login. The unsuccessful login display will be suppressed if FAILLOG_ENAB is not enabled. If ``hushlogin'' conditions are in effect, then both the successful and unsuccessful login information will be suppressed.

LOG_UNKFAIL_ENAB (boolean)
    If yes then unknown usernames will be included when a login failure is recorded. Note that this is a potential security risk; a common login failure mode is transposition of the user name and password, thus this mode will often cause passwords to accumulate in the failure logs. If this option is disabled then unknown usernames will be suppressed in login failure messages.

MAIL_CHECK_ENAB (boolean)
    If yes, the user will be notified of his or her mailbox status upon login. See MAIL_DIR for related information.

MAIL_DIR (string)
    This parameter specifies the full pathname to the directory which contains the user mailbox files. The user's login name is appended to this path to form the MAIL environment parameter - the path to the user's mailbox. This parameter must be defined; if undefined some possibly incorrect default value will be assumed. See MAIL_CHECK_ENAB for related information.

MOTD_FILE (string)
    This parameter specifies a colon-delimited list of pathnames to ``message of the day'' files. If a specified file exists, then its contents are displayed to the user upon login. If this parameter is not defined or ``hushlogin'' login conditions are in effect, this information will be suppressed.

NOLOGINS_FILE (string)
    This parameter specifies the full pathname to a file which inhibits non-root logins. If this file exists and a user other than root attempts to log in, the contents of the file will be displayed and the user will be disconnected. If this parameter is not specified then this feature will be inhibited.

OBSCURE_CHECKS_ENAB (boolean)
    If yes, the passwd program will perform additional checks before accepting a password change. The checks performed are fairly simple, and their use is recommended. These obscurity checks are bypassed if passwd is run by root. See PASS_MIN_LEN for related information.

PASS_MIN_DAYS (number)
    The minimum number of days allowed between password changes. Any password changes attempted sooner than this will be rejected. If not specified, a zero value will be assumed.

PASS_MIN_LEN (number)
    The minimum number of characters in an acceptable password. An attempt to assign a password with fewer characters will be rejected. A zero value suppresses this check. If not specified, a zero value will be assumed.

PASS_MAX_DAYS (number)
    The maximum number of days a password may be used. If the password is older than this, then the account will be locked. If not specified, a large value will be assumed.

PASS_WARN_AGE (number)
    The number of days warning given before a password expires. A zero means warning is given only upon the day of expiration, a negative value means no warning is given. If not specified, no warning will be provided.

PORTTIME_CHECKS_ENAB (boolean)
    If yes and an /etc/porttime file exists, that file will be consulted to ensure the user may login at this time on the given line. c.f. porttime(4)

QUOTAS_ENAB (boolean)
    If yes , then the user's ``ulimit,'' ``umask,'' and ``niceness'' will be initialized to the values if specified in the gecos field of the passwd file. c.f. passwd(4).

SU_NAME (string)
    This parameter assigns a command name when ``su -'' is run. For example, if the parameter is defined as ``su'', then a ps(1) listing would show the command running as ``-su''. If this parameter is undefined, then a ps(1) listing would show the name of the actual shell being run, e.g. something like ``-sh''.

SULOG_FILE (string)
    This parameter specifies a full pathname of a file in which su activity is logged. If this parameter is not specified, the logging is suppressed. Because the su command may be used when attempting to authenticate a password, either this option, or syslog should be used to note su activity. See the SYSLOG_SU_ENAB option for related information.

SYSLOG_SU_ENAB (boolean)
    If yes and login was compiled with syslog support, then all su activity will be noted through the syslog facility. See SULOG_FILE for related information.

TTYGROUP (string or number)
    The group ownership of the terminal is initialized to this group name or number. One well-known security attack involves forcing terminal control sequences upon another user's terminal line. This problem can be averted by disabling permissions which allow other users to access the terminal line, but this unfortunately prevents programs such as write from operating. Another solution is to use a version of the write program which filters out potentially dangerous character sequences, make this program ``setgid'' to a special group, assign group ownership of the terminal line to this special group, and assign permissions of 0620 to the terminal line. The TTYGROUP definition has been provided for just this situation. If this item is not defined, then the group ownership of the terminal is initialized to the user's group number. See TTYPERMS for related information.

TTYPERM (number)
    The login terminal permissions are initialized to this value. Typical values will be 0622 to permit others write access to the line or 0600 to secure the line from other users. If not specified, the terminal permissions will be initialized to 0622. See TTYGROUP for related information.

TTYTYPE_FILE (string)
    This parameter specifies the full pathname to a file which maps terminal lines to terminal types. Each line of the file contains a terminal type and a terminal line, seperated by whitespace, for example:

    	vt100 	tty01
    	wyse60	tty02
    	  .   	  .
    	  .   	  .
    	  .   	  .

    This information is used to initialize the TERM environment parameter. A line starting with a ``#'' pound sign will be treated as a comment. If this paramter is not specified, the file does not exist, or the terminal line is not found in the file, then the TERM environment parameter will not be set.

ULIMIT (long number)
    The file size limit is initialized to this value. This is supported only on systems with a ulimit, e.g. System V. If not specified, the file size limit will be initialized to some large value.

UMASK (number)
    The permission mask is initialized to this value. If not specified, the permission mask will be initialized to zero.

CROSS REFERENCE
The following cross reference shows which programs in the shadow login suite use which parameters.

login
    CONSOLE DIALUPS_CHECK_ENAB ENV_HZ ENV_SUPATH ENV_TZ ERASECHAR FAILLOG_ENAB FTMP_FILE HUSHLOGIN_FILE KILLCHAR LASTLOG_ENAB LOG_UNKFAIL_ENAB MAIL_CHECK_ENAB MAIL_DIR MOTD_FILE NOLOGINS_FILE PORTTIME_CHECKS_ENAB QUOTAS_ENAB TTYPERM TTYTYPE_FILE ULIMIT UMASK

newusers
    PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE UMASK

passwd
    OBSCURE_CHECKS_ENAB PASS_MIN_LEN

pwconv
    PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE

su  ENV_HZ ENV_SUPATH ENV_TZ HUSHLOGIN_FILE MAIL_CHECK_ENAB MAIL_DIR MOTD_FILE NOLOGIN_STR QUOTAS_ENAB SULOG_FILE SYSLOG_SU_ENAB

sulogin
    ENV_HZ ENV_SUPATH ENV_TZ MAIL_DIR QUOTAS_ENAB TTYPERM

SEE ALSO
login(1), passwd(4), faillog(4), porttime(4), faillog(8)