1 .\" Copyright (c) 1992 Drew Eckhardt, March 28, 1992
2 .\" and Copyright (c) 2002, 2004, 2005, 2008, 2010 Michael Kerrisk
4 .\" %%%LICENSE_START(VERBATIM)
5 .\" Permission is granted to make and distribute verbatim copies of this
6 .\" manual provided the copyright notice and this permission notice are
7 .\" preserved on all copies.
9 .\" Permission is granted to copy and distribute modified versions of this
10 .\" manual under the conditions for verbatim copying, provided that the
11 .\" entire resulting derived work is distributed under the terms of a
12 .\" permission notice identical to this one.
14 .\" Since the Linux kernel and libraries are constantly changing, this
15 .\" manual page may be incorrect or out-of-date. The author(s) assume no
16 .\" responsibility for errors or omissions, or for damages resulting from
17 .\" the use of the information contained herein. The author(s) may not
18 .\" have taken the same level of care in the production of this manual,
19 .\" which is licensed free of charge, as they might when working
22 .\" Formatted or processed versions of this manual, if unaccompanied by
23 .\" the source, must acknowledge the copyright and authors of this work.
26 .\" Modified by Michael Haardt <michael@moria.de>
27 .\" Modified 1993-07-23 by Rik Faith <faith@cs.unc.edu>
28 .\" Modified 1996-01-13 by Arnt Gulbrandsen <agulbra@troll.no>
29 .\" Modified 1996-01-22 by aeb, following a remark by
30 .\" Tigran Aivazian <tigran@sco.com>
31 .\" Modified 1996-04-14 by aeb, following a remark by
32 .\" Robert Bihlmeyer <robbe@orcus.ping.at>
33 .\" Modified 1996-10-22 by Eric S. Raymond <esr@thyrsus.com>
34 .\" Modified 2001-05-04 by aeb, following a remark by
35 .\" HÃ¥vard Lygre <hklygre@online.no>
36 .\" Modified 2001-04-17 by Michael Kerrisk <mtk.manpages@gmail.com>
37 .\" Modified 2002-06-13 by Michael Kerrisk <mtk.manpages@gmail.com>
38 .\" Added note on nonstandard behavior when SIGCHLD is ignored.
39 .\" Modified 2002-07-09 by Michael Kerrisk <mtk.manpages@gmail.com>
40 .\" Enhanced descriptions of 'resource' values
41 .\" Modified 2003-11-28 by aeb, added RLIMIT_CORE
42 .\" Modified 2004-03-26 by aeb, added RLIMIT_AS
43 .\" Modified 2004-06-16 by Michael Kerrisk <mtk.manpages@gmail.com>
44 .\" Added notes on CAP_SYS_RESOURCE
46 .\" 2004-11-16 -- mtk: the getrlimit.2 page, which formally included
47 .\" coverage of getrusage(2), has been split, so that the latter
48 .\" is now covered in its own getrusage.2.
50 .\" Modified 2004-11-16, mtk: A few other minor changes
51 .\" Modified 2004-11-23, mtk
52 .\" Added notes on RLIMIT_MEMLOCK, RLIMIT_NPROC, and RLIMIT_RSS
53 .\" to "CONFORMING TO"
54 .\" Modified 2004-11-25, mtk
55 .\" Rewrote discussion on RLIMIT_MEMLOCK to incorporate kernel
57 .\" Added note on RLIMIT_CPU error in older kernels
58 .\" 2004-11-03, mtk, Added RLIMIT_SIGPENDING
59 .\" 2005-07-13, mtk, documented RLIMIT_MSGQUEUE limit.
60 .\" 2005-07-28, mtk, Added descriptions of RLIMIT_NICE and RLIMIT_RTPRIO
61 .\" 2008-05-07, mtk / Peter Zijlstra, Added description of RLIMIT_RTTIME
62 .\" 2010-11-06, mtk: Added documentation of prlimit()
64 .TH GETRLIMIT 2 2015-01-22 "Linux" "Linux Programmer's Manual"
66 getrlimit, setrlimit, prlimit \- get/set resource limits
68 .B #include <sys/time.h>
70 .B #include <sys/resource.h>
72 .BI "int getrlimit(int " resource ", struct rlimit *" rlim );
74 .BI "int setrlimit(int " resource ", const struct rlimit *" rlim );
76 .BI "int prlimit(pid_t " pid ", int " resource \
77 ", const struct rlimit *" new_limit ,
79 .BI " struct rlimit *" old_limit );
82 Feature Test Macro Requirements for glibc (see
83 .BR feature_test_macros (7)):
87 _GNU_SOURCE && _FILE_OFFSET_BITS == 64
93 system calls get and set resource limits respectively.
94 Each resource has an associated soft and hard limit, as defined by the
101 rlim_t rlim_cur; /* Soft limit */
102 rlim_t rlim_max; /* Hard limit (ceiling for rlim_cur) */
107 The soft limit is the value that the kernel enforces for the
108 corresponding resource.
109 The hard limit acts as a ceiling for the soft limit:
110 an unprivileged process may set only its soft limit to a value in the
111 range from 0 up to the hard limit, and (irreversibly) lower its hard limit.
112 A privileged process (under Linux: one with the
114 capability) may make arbitrary changes to either limit value.
118 denotes no limit on a resource (both in the structure returned by
120 and in the structure passed to
125 argument must be one of:
128 The maximum size of the process's virtual memory (address space) in bytes.
129 .\" since 2.0.27 / 2.1.12
130 This limit affects calls to
135 which fail with the error
137 upon exceeding this limit.
138 Also automatic stack expansion will fail
141 that kills the process if no alternate stack
142 has been made available via
143 .BR sigaltstack (2)).
144 Since the value is a \fIlong\fP, on machines with a 32-bit \fIlong\fP
145 either this limit is at most 2 GiB, or this resource is unlimited.
152 When 0 no core dump files are created.
153 When nonzero, larger dumps are truncated to this size.
156 CPU time limit in seconds.
157 When the process reaches the soft limit, it is sent a
160 The default action for this signal is to terminate the process.
161 However, the signal can be caught, and the handler can return control to
163 If the process continues to consume CPU time, it will be sent
165 once per second until the hard limit is reached, at which time
168 (This latter point describes Linux behavior.
169 Implementations vary in how they treat processes which continue to
170 consume CPU time after reaching the soft limit.
171 Portable applications that need to catch this signal should
172 perform an orderly termination upon first receipt of
176 The maximum size of the process's data segment (initialized data,
177 uninitialized data, and heap).
178 This limit affects calls to
182 which fail with the error
184 upon encountering the soft limit of this resource.
187 The maximum size of files that the process may create.
188 Attempts to extend a file beyond this limit result in delivery of a
191 By default, this signal terminates a process, but a process can
192 catch this signal instead, in which case the relevant system call (e.g.,
198 .BR RLIMIT_LOCKS " (Early Linux 2.4 only)"
199 .\" to be precise: Linux 2.4.0-test9; no longer in 2.4.25 / 2.5.65
200 A limit on the combined number of
204 leases that this process may establish.
207 The maximum number of bytes of memory that may be locked
209 In effect this limit is rounded down to the nearest multiple
210 of the system page size.
219 Since Linux 2.6.9 it also affects the
222 operation, where it sets a maximum on the total bytes in
223 shared memory segments (see
225 that may be locked by the real user ID of the calling process.
229 locks are accounted for separately from the per-process memory
236 a process can lock bytes up to this limit in each of these
238 In Linux kernels before 2.6.9, this limit controlled the amount of
239 memory that could be locked by a privileged process.
240 Since Linux 2.6.9, no limits are placed on the amount of memory
241 that a privileged process may lock, and this limit instead governs
242 the amount of memory that an unprivileged process may lock.
244 .BR RLIMIT_MSGQUEUE " (since Linux 2.6.8)"
245 Specifies the limit on the number of bytes that can be allocated
246 for POSIX message queues for the real user ID of the calling process.
247 This limit is enforced for
249 Each message queue that the user creates counts (until it is removed)
250 against this limit according to the formula:
254 bytes = attr.mq_maxmsg * sizeof(struct msg_msg) +
255 min(attr.mq_maxmsg, MQ_PRIO_MAX) *
256 sizeof(struct posix_msg_tree_node)+
258 attr.mq_maxmsg * attr.mq_msgsize;
259 /* For message data */
261 Linux 3.4 and earlier:
262 bytes = attr.mq_maxmsg * sizeof(struct msg_msg *) +
264 attr.mq_maxmsg * attr.mq_msgsize;
265 /* For message data */
272 structure specified as the fourth argument to
277 .I posix_msg_tree_node
278 structures are kernel-internal structures.
280 The "overhead" addend in the formula accounts for overhead
281 bytes required by the implementation
282 and ensures that the user cannot
283 create an unlimited number of zero-length messages (such messages
284 nevertheless each consume some system memory for bookkeeping overhead).
286 .BR RLIMIT_NICE " (since Linux 2.6.12, but see BUGS below)"
287 Specifies a ceiling to which the process's nice value can be raised using
291 The actual ceiling for the nice value is calculated as
292 .IR "20\ \-\ rlim_cur" .
293 (This strangeness occurs because negative numbers cannot be specified
294 as resource limit values, since they typically have special meanings.
297 typically is the same as \-1.)
300 Specifies a value one greater than the maximum file descriptor number
301 that can be opened by this process.
307 to exceed this limit yield the error
309 (Historically, this limit was named
314 The maximum number of processes (or, more precisely on Linux, threads)
315 that can be created for the real user ID of the calling process.
316 Upon encountering this limit,
320 This limit is not enforced for processes that have either the
327 Specifies the limit (in pages) of the process's resident set
328 (the number of virtual pages resident in RAM).
329 This limit has effect only in Linux 2.4.x, x < 30, and there
330 affects only calls to
334 .\" As at kernel 2.6.12, this limit still does nothing in 2.6 though
335 .\" talk of making it do something has surfaced from time to time in LKML
338 .BR RLIMIT_RTPRIO " (since Linux 2.6.12, but see BUGS)"
339 Specifies a ceiling on the real-time priority that may be set for
341 .BR sched_setscheduler (2)
343 .BR sched_setparam (2).
345 .BR RLIMIT_RTTIME " (since Linux 2.6.25)"
346 Specifies a limit (in microseconds)
347 on the amount of CPU time that a process scheduled
348 under a real-time scheduling policy may consume without making a blocking
350 For the purpose of this limit,
351 each time a process makes a blocking system call,
352 the count of its consumed CPU time is reset to zero.
353 The CPU time count is not reset if the process continues trying to
354 use the CPU but is preempted, its time slice expires, or it calls
357 Upon reaching the soft limit, the process is sent a
360 If the process catches or ignores this signal and
361 continues consuming CPU time, then
363 will be generated once each second until the hard limit is reached,
364 at which point the process is sent a
368 The intended use of this limit is to stop a runaway
369 real-time process from locking up the system.
371 .BR RLIMIT_SIGPENDING " (since Linux 2.6.8)"
372 Specifies the limit on the number of signals
373 that may be queued for the real user ID of the calling process.
374 Both standard and real-time signals are counted for the purpose of
376 However, the limit is enforced only for
378 it is always possible to use
380 to queue one instance of any of the signals that are not already
381 queued to the process.
382 .\" This replaces the /proc/sys/kernel/rtsig-max system-wide limit
383 .\" that was present in kernels <= 2.6.7. MTK Dec 04
386 The maximum size of the process stack, in bytes.
387 Upon reaching this limit, a
390 To handle this signal, a process must employ an alternate signal stack
391 .RB ( sigaltstack (2)).
394 this limit also determines the amount of space used for the process's
395 command-line arguments and environment variables; for details, see
398 .\" commit c022a0acad534fd5f5d5f17280f6d4d135e74e81
399 .\" Author: Jiri Slaby <jslaby@suse.cz>
400 .\" Date: Tue May 4 18:03:50 2010 +0200
402 .\" rlimits: implement prlimit64 syscall
404 .\" commit 6a1d5e2c85d06da35cdfd93f1a27675bfdc3ad8c
405 .\" Author: Jiri Slaby <jslaby@suse.cz>
406 .\" Date: Wed Mar 24 17:06:58 2010 +0100
408 .\" rlimits: add rlimit64 structure
412 system call combines and extends the functionality of
416 It can be used to both set and get the resource limits of an arbitrary process.
420 argument has the same meaning as for
427 argument is a not NULL, then the
429 structure to which it points is used to set new values for
430 the soft and hard limits for
434 argument is a not NULL, then a successful call to
436 places the previous soft and hard limits for
440 structure pointed to by
445 argument specifies the ID of the process on which the call is to operate.
448 is 0, then the call applies to the calling process.
449 To set or get the resources of a process other than itself,
450 the caller must have the
453 real, effective, and saved set user IDs of the target process
454 must match the real user ID of the caller
456 the real, effective, and saved set group IDs of the target process
457 must match the real group ID of the caller.
458 .\" FIXME . this permission check is strange
459 .\" Asked about this on LKML, 7 Nov 2010
460 .\" "Inconsistent credential checking in prlimit() syscall"
462 On success, these system calls return 0.
463 On error, \-1 is returned, and
465 is set appropriately.
469 A pointer argument points to a location
470 outside the accessible address space.
473 The value specified in
482 .IR rlim\->rlim_max .
485 An unprivileged process tried to raise the hard limit; the
487 capability is required to do this.
490 The caller tried to increase the hard
492 limit above the maximum defined by
493 .IR /proc/sys/fs/nr_open
499 The calling process did not have permission to set limits
500 for the process specified by
504 Could not find a process with the ID specified in
509 system call is available since Linux 2.6.36.
510 Library support is available since glibc 2.13.
514 SVr4, 4.3BSD, POSIX.1-2001.
522 derive from BSD and are not specified in POSIX.1-2001;
523 they are present on the BSDs and Linux, but on few other implementations.
525 derives from BSD and is not specified in POSIX.1-2001;
526 it is nevertheless present on most implementations.
527 .BR RLIMIT_MSGQUEUE ,
535 A child process created via
537 inherits its parent's resource limits.
538 Resource limits are preserved across
541 Lowering the soft limit for a resource below the process's
542 current consumption of that resource will succeed
543 (but will prevent the process from further increasing
544 its consumption of the resource).
546 One can set the resource limits of the shell using the built-in
552 The shell's resource limits are inherited by the processes that
553 it creates to execute commands.
555 Since Linux 2.6.24, the resource limits of any process can be inspected via
556 .IR /proc/[pid]/limits ;
560 Ancient systems provided a
562 function with a similar purpose to
564 For backward compatibility, glibc also provides
566 All new applications should be written using
568 .SS C library/ kernel ABI differences
569 Since version 2.13, the glibc
573 wrapper functions no longer invoke the corresponding system calls,
576 for the reasons described in BUGS.
578 In older Linux kernels, the
582 signals delivered when a process encountered the soft and hard
584 limits were delivered one (CPU) second later than they should have been.
585 This was fixed in kernel 2.6.8.
587 In 2.6.x kernels before 2.6.17, a
589 limit of 0 is wrongly treated as "no limit" (like
591 Since Linux 2.6.17, setting a limit of 0 does have an effect,
592 but is actually treated as a limit of 1 second.
593 .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=114008066530167&w=2
595 A kernel bug means that
596 .\" See https://lwn.net/Articles/145008/
598 does not work in kernel 2.6.12; the problem is fixed in kernel 2.6.13.
600 In kernel 2.6.12, there was an off-by-one mismatch
601 between the priority ranges returned by
605 This had the effect that the actual ceiling for the nice value
607 .IR "19\ \-\ rlim_cur" .
608 This was fixed in kernel 2.6.13.
609 .\" see http://marc.theaimsgroup.com/?l=linux-kernel&m=112256338703880&w=2
612 .\" The relevant patch, sent to LKML, seems to be
613 .\" http://thread.gmane.org/gmane.linux.kernel/273462
614 .\" From: Roland McGrath <roland <at> redhat.com>
615 .\" Subject: [PATCH 7/7] make RLIMIT_CPU/SIGXCPU per-process
616 .\" Date: 2005-01-23 23:27:46 GMT
617 if a process reaches its soft
619 limit and has a handler installed for
621 then, in addition to invoking the signal handler,
622 the kernel increases the soft limit by one second.
623 This behavior repeats if the process continues to consume CPU time,
624 until the hard limit is reached,
625 at which point the process is killed.
626 Other implementations
627 .\" Tested Solaris 10, FreeBSD 9, OpenBSD 5.0
630 soft limit in this manner,
631 and the Linux behavior is probably not standards conformant;
632 portable applications should avoid relying on this Linux-specific behavior.
633 .\" FIXME . https://bugzilla.kernel.org/show_bug.cgi?id=50951
636 limit exhibits the same behavior when the soft limit is encountered.
638 Kernels before 2.4.22 did not diagnose the error
645 .IR rlim\->rlim_max .
647 .SS Representation of """large""" resource limit values on 32-bit platforms
652 wrapper functions use a 64-bit
654 data type, even on 32-bit platforms.
657 data type used in the
661 system calls is a (32-bit)
662 .IR "unsigned long" .
663 Furthermore, in Linux versions before 2.6.36,
664 the kernel represents resource limits on 32-bit platforms as
665 .IR "unsigned long" .
666 However, a 32-bit data type is not wide enough.
667 .\" https://bugzilla.kernel.org/show_bug.cgi?id=5042
668 .\" http://sources.redhat.com/bugzilla/show_bug.cgi?id=12201
669 The most pertinent limit here is
671 which specifies the maximum size to which a file can grow:
672 to be useful, this limit must be represented using a type
673 that is as wide as the type used to
674 represent file offsets\(emthat is, as wide as a 64-bit
676 (assuming a program compiled with
677 .IR _FILE_OFFSET_BITS=64 ).
679 To work around this kernel limitation,
680 if a program tried to set a resource limit to a value larger than
681 can be represented in a 32-bit
682 .IR "unsigned long" ,
685 wrapper function silently converted the limit value to
687 In other words, the requested resource limit setting was silently ignored.
689 This problem was addressed in Linux 2.6.36 with two principal changes:
691 the addition of a new kernel representation of resource limits that
692 uses 64 bits, even on 32-bit platforms;
696 system call, which employs 64-bit values for its resource limit arguments.
699 .\" https://www.sourceware.org/bugzilla/show_bug.cgi?id=12201
700 glibc works around the limitations of the
704 system calls by implementing
708 as wrapper functions that call
711 The program below demonstrates the use of
716 #define _FILE_OFFSET_BITS 64
721 #include <sys/resource.h>
723 #define errExit(msg) do { perror(msg); exit(EXIT_FAILURE); \\
727 main(int argc, char *argv[])
729 struct rlimit old, new;
733 if (!(argc == 2 || argc == 4)) {
734 fprintf(stderr, "Usage: %s <pid> [<new\-soft\-limit> "
735 "<new\-hard\-limit>]\\n", argv[0]);
739 pid = atoi(argv[1]); /* PID of target process */
743 new.rlim_cur = atoi(argv[2]);
744 new.rlim_max = atoi(argv[3]);
748 /* Set CPU time limit of target process; retrieve and display
751 if (prlimit(pid, RLIMIT_CPU, newp, &old) == \-1)
752 errExit("prlimit\-1");
753 printf("Previous limits: soft=%lld; hard=%lld\\n",
754 (long long) old.rlim_cur, (long long) old.rlim_max);
756 /* Retrieve and display new CPU time limit */
758 if (prlimit(pid, RLIMIT_CPU, NULL, &old) == \-1)
759 errExit("prlimit\-2");
760 printf("New limits: soft=%lld; hard=%lld\\n",
761 (long long) old.rlim_cur, (long long) old.rlim_max);
782 .BR capabilities (7),
785 This page is part of release 3.79 of the Linux
788 A description of the project,
789 information about reporting bugs,
790 and the latest version of this page,
792 \%http://www.kernel.org/doc/man\-pages/.