limits.conf 5 Linux-PAM Manual limits.conf configuration file for the pam_limits module 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. <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) 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 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) msqqueue 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) 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. In the limits configuration file, the '#' character introduces a comment - after which the rest of the line is ignored. The pam_limits module does its best to report configuration problems found in its configuration file via syslog3. These are some example lines which might be specified in /etc/security/limits.conf. * soft core 0 * hard rss 10000 @student hard nproc 20 @faculty soft nproc 20 @faculty hard nproc 50 ftp hard nproc 0 @student - maxlogins 4 pam_limits8, pam.d5, pam8 pam_limits was initially written by Cristian Gafton <gafton@redhat.com>