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)