LOGIN.DEFS(5)		 File Formats and Conversions		 LOGIN.DEFS(5)



NAME
       login.defs - shadow password suite configuration

DESCRIPTION
       The /etc/login.defs file defines the site-specific configuration for
       the shadow password 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, separated 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-dependent.

       The following configuration items are provided:

       CHFN_AUTH (boolean)
	   If yes, the chfn program will require authentication before making
	   any changes, unless run by the superuser.

       CHFN_RESTRICT (string)
	   This parameter specifies which values in the gecos field of the
	   /etc/passwd file may be changed by regular users using the chfn
	   program. It can be any combination of letters f, r, w, h, for Full
	   name, Room number, Work phone, and Home phone, respectively. For
	   backward compatibility, yes is equivalent to rwh and no is
	   equivalent to frwh. If not specified, only the superuser can make
	   any changes. The most restrictive setting is better achieved by not
	   installing chfn SUID.

       CHSH_AUTH (boolean)
	   If yes, the chsh program will require authentication before making
	   any changes, unless run by the superuser.

       CONSOLE (string)
	   If defined, either full pathname of a file containing device names
	   (one per line) or a ":" delimited list of device names. Root logins
	   will be allowed only upon these devices.

	   If not defined, root will be allowed on any device.

	   The device should be specified without the /dev/ prefix.

       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 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.

       CREATE_HOME (boolean)
	   Indicate if a home directory should be created by default for new
	   users.

	   This setting does not apply to system users, and can be overriden
	   on the command line.

       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.

       ENCRYPT_METHOD (string)
	   This defines the system default encryption algorithm for encrypting
	   passwords (if no algorithm are specified on the command line).

	   It can take one of these values:

	   o   DES (default)

	   o   MD5

	   o   SHA256

	   o   SHA512

	       Note: this parameter overrides the MD5_CRYPT_ENAB variable.

	   ENV_HZ (string)
	       If set, it will be used to define the HZ environment variable
	       when a user login. The value must be preceded by HZ=. A common
	       value on Linux is HZ=100.

	   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.

	   ENV_TZ (string)
	       If set, it will be used to define the TZ environment variable
	       when a user login. The value can be the name of a timezone
	       preceded by TZ= (for example TZ=CST6CDT), or the full path to
	       the file containing the timezone specification (for example
	       /etc/tzname).

	       If a full path is specified but the file does not exist or
	       cannot be read, the default is to use TZ=CST6CDT.

	   ENVIRON_FILE (string)
	       If this file exists and is readable, login environment will be
	       read from it. Every line should be in the form name=value.

	       Lines starting with a # are treated as comment lines and
	       ignored.

	   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.

	   FAILLOG_ENAB (boolean)
	       Enable logging and display of /var/log/faillog login failure
	       info.

	   FAKE_SHELL (string)
	       If set, login will execute this shell instead of the users'
	       shell specified in /etc/passwd.

	   FTMP_FILE (string)
	       If defined, login failures will be logged in this file in a
	       utmp format.

	   GID_MAX (number), GID_MIN (number)
	       Range of group IDs used for the creation of regular groups by
	       useradd, groupadd, or newusers.

	   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.

	   ISSUE_FILE (string)
	       If defined, this file will be displayed before each login
	       prompt.

	   KILLCHAR (number)
	       Terminal KILL character (025 = CTRL/U).

	       The value can be prefixed "0" for an octal value, or "0x" for
	       an hexadecimal value.

	   LASTLOG_ENAB (boolean)
	       Enable logging and display of /var/log/lastlog login time info.

	   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.

	   LOGIN_RETRIES (number)
	       Maximum number of login retries in case of bad password.

	   LOGIN_STRING (string)
	       The string used for prompting a password. The default is to use
	       "Password: ", or a translation of that string. If you set this
	       variable, the prompt will no be translated.

	       If the string contains %s, this will be replaced by the user's
	       name.

	   LOGIN_TIMEOUT (number)
	       Max time in seconds for login.

	   MAIL_CHECK_ENAB (boolean)
	       Enable checking and display of mailbox status upon login.

	       You should disable it if the shell startup files already check
	       for mail ("mailx -e" or equivalent).

	   MAIL_DIR (string)
	       The mail spool directory. This is needed to manipulate the
	       mailbox when its corresponding user account is modified or
	       deleted. If not specified, a compile-time default is used.

	   MAIL_FILE (string)
	       Defines the location of the users mail spool files relatively
	       to their home directory.

	   The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod,
	   and userdel to create, move, or delete the user's mail spool.

	   If MAIL_CHECK_ENAB is set to yes, they are also used to define the
	   MAIL environment variable.

	   MAX_MEMBERS_PER_GROUP (number)
	       Maximum members per group entry. When the maximum is reached, a
	       new group entry (line) is started in /etc/group (with the same
	       name, same password, and same GID).

	       The default value is 0, meaning that there are no limits in the
	       number of members in a group.

	       This feature (split group) permits to limit the length of lines
	       in the group file. This is useful to make sure that lines for
	       NIS groups are not larger than 1024 characters.

	       If you need to enforce such limit, you can use 25.

	       Note: split groups may not be supported by all tools (even in
	       the Shadow toolsuite). You should not use this variable unless
	       you really need it.

	   MD5_CRYPT_ENAB (boolean)
	       Indicate if passwords must be encrypted using the MD5-based
	       algorithm. If set to yes, new passwords will be encrypted using
	       the MD5-based algorithm compatible with the one used by recent
	       releases of FreeBSD. It supports passwords of unlimited length
	       and longer salt strings. Set to no if you need to copy
	       encrypted passwords to other systems which don't understand the
	       new algorithm. Default is no.

	       This variable is superceded by the ENCRYPT_METHOD variable or
	       by any command line option used to configure the encryption
	       algorithm.

	       This variable is deprecated. You should use ENCRYPT_METHOD.

	   MOTD_FILE (string)
	       If defined, ":" delimited list of "message of the day" files to
	       be displayed upon login.

	   NOLOGINS_FILE (string)
	       If defined, name of file whose presence will inhibit non-root
	       logins. The contents of this file should be a message
	       indicating why logins are inhibited.

	   OBSCURE_CHECKS_ENAB (boolean)
	       Enable additional checks upon password changes.

	   PASS_ALWAYS_WARN (boolean)
	       Warn about weak passwords (but still allow them) if you are
	       root.

	   PASS_CHANGE_TRIES (number)
	       Maximum number of attempts to change password if rejected (too
	       easy).

	   PASS_MAX_DAYS (number)
	       The maximum number of days a password may be used. If the
	       password is older than this, a password change will be forced.
	       If not specified, -1 will be assumed (which disables the
	       restriction).

	   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, -1 will be assumed (which disables
	       the restriction).

	   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.

	   PASS_MAX_DAYS, PASS_MIN_DAYS and PASS_WARN_AGE are only used at the
	   time of account creation. Any changes to these settings won't
	   affect existing accounts.

	   PASS_MAX_LEN (number), PASS_MIN_LEN (number)
	       Number of significant characters in the password for crypt().
	       PASS_MAX_LEN is 8 by default. Don't change unless your crypt()
	       is better. This is ignored if MD5_CRYPT_ENAB set to yes.

	   PORTTIME_CHECKS_ENAB (boolean)
	       Enable checking of time restrictions specified in
	       /etc/porttime.

	   QUOTAS_ENAB (boolean)
	       Enable setting of ulimit, umask, and niceness from passwd gecos
	       field.

	   SHA_CRYPT_MIN_ROUNDS (number), SHA_CRYPT_MAX_ROUNDS (number)
	       When ENCRYPT_METHOD is set to SHA256 or SHA512, this defines
	       the number of SHA rounds used by the encryption algorithm by
	       default (when the number of rounds is not specified on the
	       command line).

	       With a lot of rounds, it is more difficult to brute forcing the
	       password. But note also that more CPU resources will be needed
	       to authenticate users.

	       If not specified, the libc will choose the default number of
	       rounds (5000).

	       The values must be inside the 1000-999999999 range.

	       If only one of the SHA_CRYPT_MIN_ROUNDS or SHA_CRYPT_MAX_ROUNDS
	       values is set, then this value will be used.

	       If SHA_CRYPT_MIN_ROUNDS > SHA_CRYPT_MAX_ROUNDS, the highest
	       value will be used.

	   SULOG_FILE (string)
	       If defined, all su activity is logged to this file.

	   SU_NAME (string)
	       If defined, the command name to display when running "su -".
	       For example, if this is defined as "su" then a "ps" will
	       display the command is "-su". If not defined, then "ps" would
	       display the name of the shell actually being run, e.g.
	       something like "-sh".

	   SU_WHEEL_ONLY (boolean)
	       If yes, the user must be listed as a member of the first gid 0
	       group in /etc/group (called root on most Linux systems) to be
	       able to su to uid 0 accounts. If the group doesn't exist or is
	       empty, no one will be able to su to uid 0.

	   SYS_GID_MAX (number), SYS_GID_MIN (number)
	       Range of group IDs used for the creation of system groups by
	       useradd, groupadd, or newusers.

	   SYS_UID_MAX (number), SYS_UID_MIN (number)
	       Range of user IDs used for the creation of system users by
	       useradd or newusers.

	   SYSLOG_SG_ENAB (boolean)
	       Enable "syslog" logging of sg activity.

	   SYSLOG_SU_ENAB (boolean)
	       Enable "syslog" logging of su activity - in addition to sulog
	       file logging.

	   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".

	   UID_MAX (number), UID_MIN (number)
	       Range of user IDs used for the creation of regular users by
	       useradd or newusers.

	   ULIMIT (number)
	       Default ulimit value.

	   UMASK (number)
	       The file mode creation mask is initialized to this value. If
	       not specified, the mask will be initialized to 022.


	       useradd and newusers use this mask to set the mode of the home
	       directory they create

	       It is also used by login to define users' initial umask. Note
	       that this mask can be overriden by the user's GECOS line (if
	       QUOTAS_ENAB is set) or by the specification of a limit with the
	       K identifier in limits(5).

	   USERDEL_CMD (string)
	       If defined, this command is run when removing a user. It should
	       remove any at/cron/print jobs etc. owned by the user to be
	       removed (passed as the first argument).

	       The return code of the script is not taken into account.

	       Here is an example script, which removes the user's cron, at
	       and print jobs:

		   #! /bin/sh

		   # Check for the required argument.
		   if [ $# != 1 ]; then
			echo "Usage: $0 username"
			exit 1
		   fi

		   # Remove cron jobs.
		   crontab -r -u $1

		   # Remove at jobs.
		   # Note that it will remove any jobs owned by the same UID,
		   # even if it was shared by a different username.
		   AT_SPOOL_DIR=/var/spool/cron/atjobs
		   find $AT_SPOOL_DIR -name "[^.]*" -type f -user $1 -delete \;

		   # Remove print jobs.
		   lprm $1

		   # All done.
		   exit 0



	   USERGROUPS_ENAB (boolean)
	       Enable setting of the umask group bits to be the same as owner
	       bits (examples: 022 -> 002, 077 -> 007) for non-root users, if
	       the uid is the same as gid, and username is the same as the
	       primary group name.

	       If set to yes, userdel will remove the user's group if it
	       contains no more members, and useradd will create by default a
	       group with the name of the user.

CROSS REFERENCES
       The following cross references show which programs in the shadow
       password suite use which parameters.

       chfn

	   CHFN_AUTH CHFN_RESTRICT LOGIN_STRING

       chgpasswd
	   ENCRYPT_METHOD MAX_MEMBERS_PER_GROUP MD5_CRYPT_ENAB
	   SHA_CRYPT_MAX_ROUNDS SHA_CRYPT_MIN_ROUNDS

       chpasswd
	   ENCRYPT_METHOD MD5_CRYPT_ENAB SHA_CRYPT_MAX_ROUNDS
	   SHA_CRYPT_MIN_ROUNDS

       chsh
	   CHSH_AUTH LOGIN_STRING

       gpasswd
	   ENCRYPT_METHOD MAX_MEMBERS_PER_GROUP MD5_CRYPT_ENAB
	   SHA_CRYPT_MAX_ROUNDS SHA_CRYPT_MIN_ROUNDS

       groupadd
	   GID_MAX GID_MIN MAX_MEMBERS_PER_GROUP SYS_GID_MAX SYS_GID_MIN

       groupdel
	   MAX_MEMBERS_PER_GROUP

       groupmems
	   MAX_MEMBERS_PER_GROUP

       groupmod
	   MAX_MEMBERS_PER_GROUP

       grpck
	   MAX_MEMBERS_PER_GROUP

       grpconv
	   MAX_MEMBERS_PER_GROUP

       grpunconv
	   MAX_MEMBERS_PER_GROUP

       login

	   CONSOLE CONSOLE_GROUPS DEFAULT_HOME ENV_HZ ENV_PATH ENV_SUPATH
	   ENV_TZ ENVIRON_FILE ERASECHAR FAIL_DELAY FAILLOG_ENAB FAKE_SHELL
	   FTMP_FILE HUSHLOGIN_FILE ISSUE_FILE KILLCHAR LASTLOG_ENAB
	   LOGIN_RETRIES LOGIN_STRING LOGIN_TIMEOUT LOG_OK_LOGINS
	   LOG_UNKFAIL_ENAB MAIL_CHECK_ENAB MAIL_DIR MAIL_FILE MOTD_FILE
	   NOLOGINS_FILE PORTTIME_CHECKS_ENAB QUOTAS_ENAB TTYGROUP TTYPERM
	   TTYTYPE_FILE ULIMIT UMASK USERGROUPS_ENAB

       newgrp / sg
	   SYSLOG_SG_ENAB

       newusers
	   ENCRYPT_METHOD GID_MAX GID_MIN MAX_MEMBERS_PER_GROUP MD5_CRYPT_ENAB
	   PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE SHA_CRYPT_MAX_ROUNDS
	   SHA_CRYPT_MIN_ROUNDS SYS_GID_MAX SYS_GID_MIN SYS_UID_MAX
	   SYS_UID_MIN UID_MAX UID_MIN UMASK

       passwd
	   ENCRYPT_METHOD MD5_CRYPT_ENAB OBSCURE_CHECKS_ENAB PASS_ALWAYS_WARN
	   PASS_CHANGE_TRIES PASS_MAX_LEN PASS_MIN_LEN SHA_CRYPT_MAX_ROUNDS
	   SHA_CRYPT_MIN_ROUNDS

       pwck
	   PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE

       pwconv
	   PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE

       su

	   CONSOLE CONSOLE_GROUPS DEFAULT_HOME ENV_HZ ENVIRON_FILE ENV_PATH
	   ENV_SUPATH ENV_TZ LOGIN_STRING MAIL_CHECK_ENAB MAIL_DIR MAIL_FILE
	   QUOTAS_ENAB SULOG_FILE SU_NAME SU_WHEEL_ONLY SYSLOG_SU_ENAB
	   USERGROUPS_ENAB

       sulogin
	   ENV_HZ ENV_TZ

       useradd
	   CREATE_HOME GID_MAX GID_MIN MAIL_DIR MAX_MEMBERS_PER_GROUP
	   PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE SYS_GID_MAX SYS_GID_MIN
	   SYS_UID_MAX SYS_UID_MIN UID_MAX UID_MIN UMASK

       userdel
	   MAIL_DIR MAIL_FILE MAX_MEMBERS_PER_GROUP USERDEL_CMD
	   USERGROUPS_ENAB

       usermod
	   MAIL_DIR MAIL_FILE MAX_MEMBERS_PER_GROUP

SEE ALSO
       login(1), passwd(1), su(1), passwd(5), shadow(5), pam(8).



File Formats and Conversions	  07/24/2009			 LOGIN.DEFS(5)