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login.conf - login class capability database


Resource Limits
Reserved Capabilities
See Also


/etc/login.conf, ~/.login_conf


login.conf contains various attributes and capabilities of login classes. A login class (an optional annotation against each record in the user account database, /etc/master.passwd) determines session accounting, resource limits and user environment settings. It is used by various programs in the system to set up a user’s login environment and to enforce policy, accounting and administrative restrictions. It also provides the means by which users are able to be authenticated to the system and the types of authentication available. Attributes in addition to the ones described here are available with third-party packages.

A special record "default" in the system user class capability database /etc/login.conf is used automatically for any non-root user without a valid login class in /etc/master.passwd. A user with a uid of 0 without a valid login class will use the record "root" if it exists, or "default" if not.

.Fx , users may individually create a file called .login_conf in their home directory using the same format, consisting of a single entry with a record id of "me". If present, this file is used by login(1) to set user-defined environment settings which override those specified in the system login capabilities database. Only a subset of login capabilities may be overridden, typically those which do not involve authentication, resource limits and accounting.

Records in a class capabilities database consist of a number of colon-separated fields. The first entry for each record gives one or more names that a record is to be known by, each separated by a ’|’ character. The first name is the most common abbreviation. The last name given should be a long name that is more descriptive of the capability entry, and all others are synonyms. All names but the last should be in lower case and contain no blanks; the last name may contain upper case characters and blanks for readability.

The default /etc/login.conf shipped with
.Fx is an out of the box configuration. Whenever changes to this, or the user’s ~/.login_conf, file are made, the modifications will not be picked up until cap_mkdb(1) is used to compile the file into a database. This database file will have a .db extension and is accessed through cgetent(3). See getcap(3) for a more in-depth description of the format of a capability database.


Fields within each record in the database follow the getcap(3) conventions for boolean, type string ‘=’ and type numeric ‘#’, although type numeric is deprecated in favour of the string format and either form is accepted for a numeric datum. Values fall into the following categories:
bool If the name is present, then the boolean value is true; otherwise, it is false
file Path name to a data file
program Path name to an executable file
list A list of values (or pairs of values) separated by commas or spaces
path A space or comma separated list of path names, following the usual csh conventions (leading tilde with and without username being expanded to home directories etc.)
number A numeric value, either decimal (default), hexadecimal (with leading 0x), or octal (with a leading 0). With a numeric type, only one numeric value is allowed. Numeric types may also be specified in string format (i.e., the capability tag being delimited from the value by ’=’ instead of ’#’). Whichever method is used, then all records in the database must use the same method to allow values to be correctly overridden in interpolated records.
size A number which expresses a size. The default interpretation of a value is the number of bytes, but a suffix may specify alternate units:
b explicitly selects 512-byte blocks
k selects kilobytes (1024 bytes)
m specifies a multiplier of 1 megabyte (1048576 bytes),
g specifies units of gigabytes, and
t represents terabytes.
A size value is a numeric quantity and case of the suffix is not significant. Concatenated values are added together.
time A period of time, by default in seconds. A prefix may specify a different unit:
y indicates the number of 365 day years,
w indicates the number of weeks,
d the number of days,
h the number of hours,
m the number of minutes, and
s the number of seconds.
Concatenated values are added together. For example, 2 hours and 40 minutes may be written either as 9600s, 160m or 2h40m.

The usual convention to interpolate capability entries using the special tc=value notation may be used.


"Name Type Notes Description
"coredumpsize size Maximum coredump size limit.
"cputime time CPU usage limit.
"datasize size Maximum data size limit.
"filesize size Maximum file size limit.
"maxproc number Maximum number of processes.
"memorylocked size Maximum locked in core memory size limit.
"memoryuse size Maximum of core memory use size limit.
"openfiles number Maximum number of open files per process.
"sbsize size Maximum permitted socketbuffer size.
"vmemoryuse size Maximum permitted total VM usage per process.
"stacksize size Maximum stack size limit.

These resource limit entries actually specify both the maximum and current limits (see getrlimit(2)). The current (soft) limit is the one normally used, although the user is permitted to increase the current limit to the maximum (hard) limit. The maximum and current limits may be specified individually by appending a -max or -cur to the capability name.


"Name Type Notes Description
"charset string Set $MM_CHARSET environment variable to the specified
"hushlogin bool false Same as having a ~/.hushlogin file.
"ignorenologin bool false Login not prevented by nologin.
"ftp-chroot bool false Limit FTP access with
chroot(2) to the HOME directory of the user. See ftpd(8) for details.
"label string Default MAC policy; see maclabel(7).
"lang string Set $LANG environment variable to the specified value.
"manpath path Default search path for manpages.
"nocheckmail bool false Display mail status at login.
"nologin file If the file exists it will be displayed and
the login session will be terminated.
"path path /bin /usr/bin Default search path.
"priority number Initial priority (nice) level.
"requirehome bool false Require a valid home directory to login.
"setenv list A comma-separated list of environment variables and
values to which they are to be set.
"shell prog Session shell to execute rather than the shell specified in the passwd file. The SHELL environment variable will contain the shell specified in the password file.
"term string Default terminal type if not able to determine from other means.
"timezone string Default value of $TZ environment variable.
"umask number 022 Initial umask. Should always have a leading 0 to
ensure octal interpretation.
"welcome file /etc/motd File containing welcome message.


"Name Type Notes Description
"copyright file File containing additional copyright information
"host.allow list List of remote host wildcards from which users in
the class may access.
"host.deny list List of remote host wildcards from which users in the class may not access.
"login_prompt string The login prompt given by login(1)
"login-backoff number 3 The number of login attempts allowed before the backoff delay is inserted after each subsequent attempt.
"login-retries number 10 The number of login attempts allowed before the login fails.
"passwd_format string md5 The encryption format that new or changed passwords will use. Valid values include "des", "md5" and "blf". NIS clients using a non- Fx NIS server should probably use "des".
"passwd_prompt string The password prompt presented by login(1)
"times.allow list List of time periods during which logins are allowed.
"times.deny list List of time periods during which logins are disallowed.
"ttys.allow list List of ttys and ttygroups which users in the class may use for access.
"ttys.deny list List of ttys and ttygroups which users in the class may not use for access.
"warnexpire time Advance notice for pending account expiry.
"warnpassword time Advance notice for pending password expiry.

These fields are intended to be used by passwd(1) and other programs in the login authentication system.

Capabilities that set environment variables are scanned for both ‘~’ and ‘$’ characters, which are substituted for a user’s home directory and name respectively. To pass these characters literally into the environment variable, escape the character by preceding it with a backslash ’#146;.

The host.allow and host.deny entries are comma separated lists used for checking remote access to the system, and consist of a list of hostnames and/or IP addresses against which remote network logins are checked. Items in these lists may contain wildcards in the form used by shell programs for wildcard matching (See fnmatch(3) for details on the implementation). The check on hosts is made against both the remote system’s Internet address and hostname (if available). If both lists are empty or not specified, then logins from any remote host are allowed. If host.allow contains one or more hosts, then only remote systems matching any of the items in that list are allowed to log in. If host.deny contains one or more hosts, then a login from any matching hosts will be disallowed.

The times.allow and times.deny entries consist of a comma-separated list of time periods during which the users in a class are allowed to be logged in. These are expressed as one or more day codes followed by a start and end times expressed in 24 hour format, separated by a hyphen or dash. For example, MoThSa0200-1300 translates to Monday, Thursday and Saturday between the hours of 2 am and 1 p.m.. If both of these time lists are empty, users in the class are allowed access at any time. If times.allow is specified, then logins are only allowed during the periods given. If times.deny is specified, then logins are denied during the periods given, regardless of whether one of the periods specified in times.allow applies.

Note that login(1) enforces only that the actual login falls within periods allowed by these entries. Further enforcement over the life of a session requires a separate daemon to monitor transitions from an allowed period to a non-allowed one.

The ttys.allow and ttys.deny entries contain a comma-separated list of tty devices (without the /dev/ prefix) that a user in a class may use to access the system, and/or a list of ttygroups (See getttyent(3) and ttys(5) for information on ttygroups). If neither entry exists, then the choice of login device used by the user is unrestricted. If only ttys.allow is specified, then the user is restricted only to ttys in the given group or device list. If only ttys.deny is specified, then the user is prevented from using the specified devices or devices in the group. If both lists are given and are non-empty, the user is restricted to those devices allowed by ttys.allow that are not available by ttys.deny.

The minpasswordlen and minpasswordcase facilities for enforcing restrictions on password quality, which used to be supported by login.conf, have been superseded by the pam_passwdqc(8) PAM module.


The following capabilities are reserved for the purposes indicated and may be supported by third-party software. They are not implemented in the base system.
"Name Type Notes Description
"accounted bool false Enable session time accounting for all users
in this class.
"autodelete time Time after expiry when account is auto-deleted.
"bootfull bool false Enable ’boot only if ttygroup is full’ strategy
when terminating sessions.
"daytime time Maximum login time per day.
"expireperiod time Time for expiry allocation.
"graceexpire time Grace days for expired account.
"gracetime time Additional grace login time allowed.
"host.accounted list List of remote host wildcards from which
login sessions will be accounted.
"host.exempt list List of remote host wildcards from which login session accounting is exempted.
"idletime time Maximum idle time before logout.
"minpasswordlen number 6 The minimum length a local
password may be.
"mixpasswordcase bool true Whether passwd(1) will warn the user if an all lower case password is entered.
"monthtime time Maximum login time per month.
"passwordtime time Used by
passwd(1) to set next password expiry date.
"refreshtime time New time allowed on account refresh.
"refreshperiod str How often account time is refreshed.
"sessiontime time Maximum login time per session.
"sessionlimit number Maximum number of concurrent
login sessions on ttys in any group.
"ttys.accounted list List of ttys and ttygroups for which login accounting is active.
"ttys.exempt list List of ttys and ttygroups for which login accounting is exempt.
"warntime time Advance notice for pending out-of-time.
"weektime time Maximum login time per week.

The ttys.accounted and ttys.exempt fields operate in a similar manner to ttys.allow and ttys.deny as explained above. Similarly with the host.accounted and host.exempt lists.


cap_mkdb(1), login(1), chroot(2), getcap(3), getttyent(3), login_cap(3), login_class(3), pam(3), passwd(5), ttys(5), ftpd(8), pam_passwdqc(8)

Created by Blin Media, 2008-2013