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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>

	   ·   a username

	   ·   a groupname, with @group syntax. This should not be confused
	       with netgroups.

	   ·   the wildcard *, for default entry.

	   ·   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.

	   ·   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.

	   ·   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.

	   ·   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.

	   NOTE: group and wildcard limits are not applied to the root user.
	   To set a limit for the root user, this field must contain the
	   literal username root.

       <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)

	   chroot
	       the directory to chroot the user to

       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
	   root		   hard	   core		   100000
	   *		   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(7), 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)
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