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NAME | DESCRIPTION | CROSS REFERENCES | BUGS | SEE ALSO | COLOPHON |
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LOGIN.DEFS(5) File Formats and Configuration LOGIN.DEFS(5)
login.defs - shadow password suite configuration
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_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.
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.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to
the PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
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.
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.
FAKE_SHELL (string)
If set, login will execute this shell instead of the users'
shell specified in /etc/passwd.
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).
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.
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_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.
This will most likely be overridden by PAM, since the default
pam_unix module has its own built in of 3 retries. However,
this is a safe fallback in case you are using an
authentication module that does not enforce PAM_MAXTRIES.
LOGIN_TIMEOUT (number)
Max time in seconds for login.
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.
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.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to
the PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
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.
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.
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.
Note: This only affect the generation of group passwords. The
generation of user passwords is done by PAM and subject to
the PAM configuration. It is recommended to set this variable
consistently with the PAM configuration.
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".
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).
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 pam_umask as the default umask value.
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)
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.
The following cross references show which programs in the shadow
password suite use which parameters.
chfn
CHFN_RESTRICT
chgpasswd
ENCRYPT_METHOD MAX_MEMBERS_PER_GROUP MD5_CRYPT_ENAB
SHA_CRYPT_MAX_ROUNDS SHA_CRYPT_MIN_ROUNDS
chpasswd
SHA_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
lastlog
LASTLOG_UID_MAX
login
CONSOLE_GROUPS DEFAULT_HOME ERASECHAR FAIL_DELAY FAKE_SHELL
HUSHLOGIN_FILE KILLCHAR LOGIN_RETRIES LOGIN_TIMEOUT
LOG_OK_LOGINS LOG_UNKFAIL_ENAB TTYGROUP TTYPERM TTYTYPE_FILE
USERGROUPS_ENAB
newgrp / sg
SYSLOG_SG_ENAB
newusers
ENCRYPT_METHOD GID_MAX GID_MIN MAX_MEMBERS_PER_GROUP
MD5_CRYPT_ENAB HOME_MODE 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
su
CONSOLE_GROUPS DEFAULT_HOME ENV_PATH ENV_SUPATH SULOG_FILE
SU_NAME SYSLOG_SU_ENAB
useradd
CREATE_HOME GID_MAX GID_MIN HOME_MODE LASTLOG_UID_MAX
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
LASTLOG_UID_MAX MAIL_DIR MAIL_FILE MAX_MEMBERS_PER_GROUP
Much of the functionality that used to be provided by the shadow
password suite is now handled by PAM. Thus, /etc/login.defs is no
longer used by passwd(1), or less used by login(1), and su(1).
Please refer to the corresponding PAM configuration files
instead.
login(1), passwd(1), su(1), passwd(5), shadow(5), pam(8).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about
the project can be found at
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug
report for this manual page, send it to
pkg-shadow-devel@alioth-lists.debian.net. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2024-06-15. (At that
time, the date of the most recent commit that was found in the
repository was 2024-06-13.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
shadow-utils 4.14.0 06/15/2024 LOGIN.DEFS(5)
Pages that refer to this page: chfn(1), chfn(1@@shadow-utils), chsh(1), chsh(1@@shadow-utils), getsubids(1), login(1), login(1@@shadow-utils), newgidmap(1), newuidmap(1), runuser(1), su(1), su(1@@shadow-utils), securetty(5), subgid(5), subuid(5), agetty(8), chgpasswd(8), chpasswd(8), groupadd(8), groupmod(8), newusers(8), pam_unix(8), pam_usertype(8), pwconv(8), useradd(8), userdel(8), usermod(8)
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HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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