limits.conf(5) — Linux manual page


LIMITS.CONF(5)                Linux-PAM Manual                LIMITS.CONF(5)

NAME         top

       limits.conf - configuration file for the pam_limits module

DESCRIPTION         top

       The 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:


       The fields listed above should be filled as follows:


           •   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.


               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.

               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. .


               limits the core file size (KB)

               maximum data size (KB)

               maximum filesize (KB)

               maximum locked-in-memory address space (KB)

               maximum number of open file descriptors

               maximum resident set size (KB) (Ignored in Linux 2.4.30 and

               maximum stack size (KB)

               maximum CPU time (minutes)

               maximum number of processes

               address space limit (KB)

               maximum number of logins for this user (this limit does not
               apply to user with uid=0)

               maximum number of all logins on system; user is not allowed
               to log-in if total number of all user logins is greater than
               specified number (this limit does not apply to user with

               the priority to run user process with (negative values boost
               process priority)

               maximum locked files (Linux 2.4 and higher)

               maximum number of pending signals (Linux 2.6 and higher)

               maximum memory used by POSIX message queues (bytes) (Linux
               2.6 and higher)

               maximum nice priority allowed to raise to (Linux 2.6.12 and
               higher) values: [-20,19]

               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         top

       These are some example lines which might be specified in

           *               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         top

       pam_limits(8), pam.d(5), pam(8), getrlimit(2)getrlimit(3p)

AUTHOR         top

       pam_limits was initially written by Cristian Gafton

COLOPHON         top

       This page is part of the linux-pam (Pluggable Authentication Modules
       for Linux) project.  Information about the project can be found at 
       ⟨⟩.  If you have a bug report for this manual
       page, see ⟨//⟩.  This page was obtained from the
       tarball Linux-PAM-1.3.0.tar.bz2 fetched from
       ⟨⟩ on 2020-11-01.  If you discover
       any rendering problems in this HTML version of the page, or you be‐
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       COLOPHON (which is not part of the original manual page), send a mail

Linux-PAM Manual                 04/01/2016                   LIMITS.CONF(5)

Pages that refer to this page: htop(1)pam_limits(8)