PAM_LIMITS(8) Linux-PAM Manual PAM_LIMITS(8)NAME
pam_limits - PAM module to limit resources
SYNOPSIS
pam_limits.so [conf=/path/to/limits.conf] [debug] [set_all] [utmp_early] [noaudit]
DESCRIPTION
The pam_limits PAM module sets limits on the system resources that can be obtained in a user-session. Users of uid=0 are affected by this
limits, too.
By default limits are taken from the /etc/security/limits.conf config file. Then individual *.conf files from the /etc/security/limits.d/
directory are read. The files are parsed one after another in the order of "C" locale. The effect of the individual files is the same as if
all the files were concatenated together in the order of parsing. If a config file is explicitly specified with a module option then the
files in the above directory are not parsed.
The module must not be called by a multithreaded application.
If Linux PAM is compiled with audit support the module will report when it denies access based on limit of maximum number of concurrent
login sessions.
OPTIONS
conf=/path/to/limits.conf
Indicate an alternative limits.conf style configuration file to override the default.
debug
Print debug information.
set_all
Set the limits for which no value is specified in the configuration file to the one from the process with the PID 1.
utmp_early
Some broken applications actually allocate a utmp entry for the user before the user is admitted to the system. If some of the services
you are configuring PAM for do this, you can selectively use this module argument to compensate for this behavior and at the same time
maintain system-wide consistency with a single limits.conf file.
noaudit
Do not report exceeded maximum logins count to the audit subsystem.
MODULE TYPES PROVIDED
Only the session module type is provided.
RETURN VALUES
PAM_ABORT
Cannot get current limits.
PAM_IGNORE
No limits found for this user.
PAM_PERM_DENIED
New limits could not be set.
PAM_SERVICE_ERR
Cannot read config file.
PAM_SESSION_ERR
Error recovering account name.
PAM_SUCCESS
Limits were changed.
PAM_USER_UNKNOWN
The user is not known to the system.
FILES
/etc/security/limits.conf
Default configuration file
EXAMPLES
For the services you need resources limits (login for example) put a the following line in /etc/pam.d/login as the last line for that
service (usually after the pam_unix session line):
#%PAM-1.0
#
# Resource limits imposed on login sessions via pam_limits
#
session required pam_limits.so
Replace "login" for each service you are using this module.
SEE ALSO limits.conf(5), pam.d(5), pam(8).
AUTHORS
pam_limits was initially written by Cristian Gafton <gafton@redhat.com>
Linux-PAM Manual 09/19/2013 PAM_LIMITS(8)
Check Out this Related Man Page
LIMITS.CONF(5) Linux-PAM Manual LIMITS.CONF(5)NAME
limits.conf - configuration file for the pam_limits module
DESCRIPTION
The pam_limits.so module applies ulimit limits, nice priority and number of simultaneous login sessions limit to user login sessions. This
description of the configuration file syntax applies to the /etc/security/limits.conf file and *.conf files in the /etc/security/limits.d
directory.
The syntax of the lines is as follows:
<domain><type><item><value>
The fields listed above should be filled as follows:
<domain>
o a username
o a groupname, with @group syntax. This should not be confused with netgroups.
o the wildcard *, for default entry.
o the wildcard %, for maxlogins limit only, can also be used with %group syntax. If the % wildcard is used alone it is identical to
using * with maxsyslogins limit. With a group specified after % it limits the total number of logins of all users that are member
of the group.
o an uid range specified as <min_uid>:<max_uid>. If min_uid is omitted, the match is exact for the max_uid. If max_uid is omitted,
all uids greater than or equal min_uid match.
o a gid range specified as @<min_gid>:<max_gid>. If min_gid is omitted, the match is exact for the max_gid. If max_gid is omitted,
all gids greater than or equal min_gid match. For the exact match all groups including the user's supplementary groups are
examined. For the range matches only the user's primary group is examined.
o a gid specified as %:<gid> applicable to maxlogins limit only. It limits the total number of logins of all users that are member of
the group with the specified gid.
<type>
hard
for enforcing hard resource limits. These limits are set by the superuser and enforced by the Kernel. The user cannot raise his
requirement of system resources above such values.
soft
for enforcing soft resource limits. These limits are ones that the user can move up or down within the permitted range by any
pre-existing hard limits. The values specified with this token can be thought of as default values, for normal system usage.
-
for enforcing both soft and hard resource limits together.
Note, if you specify a type of '-' but neglect to supply the item and value fields then the module will never enforce any limits on
the specified user/group etc. .
<item>
core
limits the core file size (KB)
data
maximum data size (KB)
fsize
maximum filesize (KB)
memlock
maximum locked-in-memory address space (KB)
nofile
maximum number of open files
rss
maximum resident set size (KB) (Ignored in Linux 2.4.30 and higher)
stack
maximum stack size (KB)
cpu
maximum CPU time (minutes)
nproc
maximum number of processes
as
address space limit (KB)
maxlogins
maximum number of logins for this user except for this with uid=0
maxsyslogins
maximum number of all logins on system
priority
the priority to run user process with (negative values boost process priority)
locks
maximum locked files (Linux 2.4 and higher)
sigpending
maximum number of pending signals (Linux 2.6 and higher)
msgqueue
maximum memory used by POSIX message queues (bytes) (Linux 2.6 and higher)
nice
maximum nice priority allowed to raise to (Linux 2.6.12 and higher) values: [-20,19]
rtprio
maximum realtime priority allowed for non-privileged processes (Linux 2.6.12 and higher)
All items support the values -1, unlimited or infinity indicating no limit, except for priority and nice.
If a hard limit or soft limit of a resource is set to a valid value, but outside of the supported range of the local system, the system may
reject the new limit or unexpected behavior may occur. If the control value required is used, the module will reject the login if a limit
could not be set.
In general, individual limits have priority over group limits, so if you impose no limits for admin group, but one of the members in this
group have a limits line, the user will have its limits set according to this line.
Also, please note that all limit settings are set per login. They are not global, nor are they permanent; existing only for the duration of
the session. One exception is the maxlogin option, this one is system wide. But there is a race, concurrent logins at the same time will
not always be detect as such but only counted as one.
In the limits configuration file, the '#' character introduces a comment - after which the rest of the line is ignored.
The pam_limits module does report configuration problems found in its configuration file and errors via syslog(3).
EXAMPLES
These are some example lines which might be specified in /etc/security/limits.conf.
* soft core 0
* hard nofile 512
@student hard nproc 20
@faculty soft nproc 20
@faculty hard nproc 50
ftp hard nproc 0
@student - maxlogins 4
:123 hard cpu 5000
@500: soft cpu 10000
600:700 hard locks 10
SEE ALSO pam_limits(8), pam.d(5), pam(8), getrlimit(2)getrlimit(3p)AUTHOR
pam_limits was initially written by Cristian Gafton <gafton@redhat.com>
Linux-PAM Manual 09/19/2013 LIMITS.CONF(5)