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.
Please note that the parameters in this configuration file control the
behavior of the tools from the shadow-utils component. None of these
tools uses the PAM mechanism, and the utilities that use PAM (such as
the passwd command) should be configured elsewhere. The only values
that affect PAM modules are ENCRYPT_METHOD and SHA_CRYPT_MAX_ROUNDS for
pam_unix module, FAIL_DELAY for pam_faildelay module, and UMASK for
pam_umask module. Refer to pam(8) for more information.
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.
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).
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 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.
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.
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 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 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 1000-999,999,999 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.
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.
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
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.
CROSS REFERENCES
The following cross references show which programs in the shadow
password suite use which parameters.
chgpasswd
ENCRYPT_METHOD MAX_MEMBERS_PER_GROUP MD5_CRYPT_ENAB
SHA_CRYPT_MAX_ROUNDS SHA_CRYPT_MIN_ROUNDS
chpasswd
ENCRYPT_METHOD MD5_CRYPT_ENABSHA_CRYPT_MAX_ROUNDS
SHA_CRYPT_MIN_ROUNDS
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
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 SUB_GID_COUNT SUB_GID_MAX SUB_GID_MIN
SUB_UID_COUNT SUB_UID_MAX SUB_UID_MIN SYS_GID_MAX SYS_GID_MIN
SYS_UID_MAX SYS_UID_MIN UID_MAX UID_MIN UMASK
pwck
PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
pwconv
PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
useradd
CREATE_HOME GID_MAX GID_MIN MAIL_DIR MAX_MEMBERS_PER_GROUP
PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE SUB_GID_COUNT SUB_GID_MAX
SUB_GID_MIN SUB_UID_COUNT SUB_UID_MAX SUB_UID_MIN 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).
shadow-utils 4.6 08/09/2019 LOGIN.DEFS(5)
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