1 .\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au>
2 .\" All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, is permitted provided that the following conditions
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10 .\" 2. Redistributions in binary form must reproduce the above copyright
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13 .\" 3. This work was done expressly for inclusion into FreeBSD. Other use
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27 .Nd set or display process resource limits
33 .Op Fl cdflmnstu Op val
37 .Op Fl cdflmnstu Op val
45 .Op Fl cdflmnstu Op val
49 .Op Fl cdflmnstu Op val
55 either prints or sets kernel resource limits, and may optionally set
56 environment variables like
58 and run a program with the selected resources.
63 .Bl -hang -width indent
64 .It Nm limits Op Ar limitflags
68 This usage sets limits according to
70 optionally sets environment variables given as
72 pairs, and then runs the specified command.
73 .It Nm limits Op Ar limitflags
75 This usage determines values of resource settings according to
77 does not attempt to set them and outputs these values to
79 By default, this will output the current kernel resource settings
80 active for the calling process.
85 flags, you may also display the current resource settings modified
86 by the the appropriate login class resource limit entries from
89 login capabilities database.
90 .It Nm limits Fl e Op Ar limitflags
92 This usage determines values of resource settings according to
94 but does not set them itself.
95 Like the previous usage it outputs these values to standard
96 output, except that it will emit them in
98 format, suitable for the calling shell.
99 The calling shell is determined by examining the entries in the
101 filesystem for the parent process.
102 If the shell is known (i.e. it is one of sh, csh, bash, tcsh, ksh,
105 emits 'limit' or 'ulimit' commands in the format understood by
107 If the name of the shell cannot be determined, then the 'ulimit'
112 This is very useful for setting limits used by scripts, or prior
113 launching of daemons and other background tasks with specific
114 resource limit settings, and provides the benefit of allowing
115 global configuration of maximum resource usage by maintaining a
116 central database of settings in the login class database.
118 Within a shell script,
120 will normally be used with eval within backticks as follows:
122 .Dl eval `limits -e -C daemon`
124 which causes the output of
126 to be evaluated and set by the current shell.
129 The value of limitflags specified in the above contains one or more of the
132 .Bl -tag -width "-d [limit]"
134 Use current resource values, modified by the resource entries applicable
135 for the login class "class".
137 Use current resource values, modified by the resource entries applicable
138 to the login class which "user" belongs to.
139 If the user does not belong to a class, then the resource capabilities
140 for the "default" class are used, if it exists, or the "root" class if
141 the user is a superuser account.
143 Select display or setting of "soft" (or current) resource limits.
144 If specific limits settings follow this switch, only soft limits are
145 affected unless overridden later with either the
151 Select display or setting of "hard" (or maximum) resource limits.
152 If specific limits settings follow this switch, only hard limits are
153 affected until overridden later with either the
159 Select display or setting of both "soft" (current) or "hard" (maximum)
161 If specific limits settings follow this switch, both soft and hard
162 limits are affected until overridden later with either the
168 Select "eval mode" formatting for output.
169 This is valid only on display mode and cannot be used when running a
171 The exact syntax used for output depends upon the type of shell from
180 Select or set (if 'limit' is specified) the
183 A value of 0 disables core dumps.
185 Select or set (if 'limit' is specified) the
203 resource limit. The system-wide limit on the maximum number of
204 open files per process can be viewed using the 'sysctl kern.maxfilesperproc'
205 command. The total number of simultaneously open files in the entire
206 system is limited to the value displayed by the 'sysctl kern.maxfiles'
219 resource limit. The system-wide limit on the maximum number of processes
220 allowed per UID can be viewed using the 'sysctl kern.maxprocperuid' command.
221 The maximum number of processes that can be running simultaneously
222 in the entire system is limited to the value given by
223 the 'sysctl kern.maxproc' command.
227 in the above set of flags consist of either the
234 for an infinite (or kernel-defined maximum)
235 limit, or a numeric value maybe followed by a suffix.
236 Values which relate to size default to a value in bytes, or one of the
237 following suffixes may be used as a multiplier:
239 .Bl -tag -offset indent -width "xxxx" -compact
243 kilobytes (1024 bytes).
245 megabytes (1024*1024 bytes).
254 resource defaults to a number of seconds, but a multiplier may be
255 used, and as with size values, multiple values separated by a valid
256 suffix are added together:
257 .Bl -tag -offset indent -width "xxxx" -compact
277 to completely ignore the environment it inherits.
279 This option forces all resource settings to be displayed even if
280 other specific resource settings have been specified.
281 For example, if you wish to disable core dumps when starting up
282 the usenet news system, but wish to set all other resource settings
283 as well that apply to the 'news' account, you might use:
285 .Dl eval `limits -U news -aBec 0`
289 call, only the superuser may raise process "hard" resource limits.
290 Non-root users may, however, lower them or change "soft" resource limits
291 within to any value below the hard limit.
292 When invoked to execute a program, the failure of
294 to raise a hard limit is considered a fatal error.
298 exits with EXIT_FAILURE if usage is incorrect in any way; i.e. an invalid
299 option, or set/display options are selected in the same invocation,
301 is used when running a program, etc.
302 When run in display or eval mode,
304 exits with a status of EXIT_SUCCESS.
305 When run in command mode and execution of the command succeeds, the exit status
306 will be whatever the executed program returns.
319 does not handle commands with equal (``='') signs in their
320 names, for obvious reasons.
322 When eval output is selected, the
324 filesystem must be installed
325 and mounted for the shell to be correctly determined, and therefore
326 output syntax correct for the running shell.
327 The default output is valid for
329 so this means that any
332 in eval mode prior mounting
334 may only occur in standard bourne
338 makes no effort to ensure that resource settings emitted or displayed
339 are valid and settable by the current user.
340 Only a superuser account may raise hard limits, and when doing so
343 kernel will silently lower limits to values less than
344 specified if the values given are too high.