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>