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 overridden
on the command line.
DEFAULT_HOME (boolean)
Indicate if login is allowed if we can't cd to the home
directory. Default is 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: DES (default), MD5,
SHA256, SHA512. MD5 and DES should not be used for new hashes,
see crypt(5) for recommendations.
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 is a colon separated list of
paths (for example /bin:/usr/bin) and can be preceded by PATH=.
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 is a colon separated list of
paths (for example /sbin:/bin:/usr/sbin:/usr/bin) and can be preceded
by PATH=. The default value is
PATH=/sbin:/bin:/usr/sbin:/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.
The default value for GID_MIN (resp. GID_MAX) is
1000 (resp. 60000).
HMAC_CRYPTO_ALGO (string)
Used to select the HMAC cryptography algorithm that the
pam_timestamp module is going to use to calculate the keyed-hash message
authentication code.
Note: Check hmac(3) to see the possible algorithms that are
available in your system.
HOME_MODE (number)
The mode for new home directories. If not specified, the
UMASK is used to create the mode.
useradd and newusers use this to set the mode of the
home directory they create.
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.
LASTLOG_UID_MAX (number)
Highest user ID number for which the lastlog entries
should be updated. As higher user IDs are usually tracked by remote user
identity and authentication services there is no need to create a huge sparse
lastlog file for them.
No LASTLOG_UID_MAX option present in the configuration
means that there is no user ID limit for writing lastlog entries.
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 not 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. The parameter CREATE_MAIL_SPOOL in
/etc/default/useradd determines whether the mail spool should be
created.
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 superseded 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.
NONEXISTENT (string)
If a system account intentionally does not have a home
directory that exists, this string can be provided in the /etc/passwd entry
for the account to indicate this. The result is that pwck will not emit a
spurious warning for this account.
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, 0 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
value of -1 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 resource limits from /etc/limits and
ulimit, umask, and niceness from the user's 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 force 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), which is orders of magnitude too low for modern hardware.
The values must be inside the 1000-999,999,999 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.
SUB_GID_MIN (number), SUB_GID_MAX (number),
SUB_GID_COUNT (number)
If /etc/subuid exists, the commands
useradd and
newusers (unless the user already have subordinate group IDs) allocate
SUB_GID_COUNT unused group IDs from the range
SUB_GID_MIN to
SUB_GID_MAX for each new user.
The default values for SUB_GID_MIN, SUB_GID_MAX,
SUB_GID_COUNT are respectively 100000, 600100000 and 65536.
SUB_UID_MIN (number), SUB_UID_MAX (number),
SUB_UID_COUNT (number)
If /etc/subuid exists, the commands
useradd and
newusers (unless the user already have subordinate user IDs) allocate
SUB_UID_COUNT unused user IDs from the range
SUB_UID_MIN to
SUB_UID_MAX for each new user.
The default values for SUB_UID_MIN, SUB_UID_MAX,
SUB_UID_COUNT are respectively 100000, 600100000 and 65536.
SYS_GID_MAX (number), SYS_GID_MIN (number)
Range of group IDs used for the creation of system groups
by
useradd,
groupadd, or
newusers.
The default value for SYS_GID_MIN (resp.
SYS_GID_MAX) is 101 (resp. GID_MIN-1).
SYS_UID_MAX (number), SYS_UID_MIN (number)
Range of user IDs used for the creation of system users
by
useradd or
newusers.
The default value for SYS_UID_MIN (resp.
SYS_UID_MAX) is 101 (resp. UID_MIN-1).
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.
TTYGROUP can be either the name of a group or a numeric
group identifier.
If TTYGROUP is not defined, then the group ownership of the
terminal is set to the user's primary group. If TTYPERM is not defined, then
the permissions are set to 0600.
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.
The default value for UID_MIN (resp. UID_MAX) is
1000 (resp. 60000).
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 if HOME_MODE is not set.
It is also used by login to define users' initial umask.
Note that this mask can be overridden 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.