1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
|
.\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, is permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice immediately at the beginning of the file, without modification,
.\" this list of conditions, and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. This work was done expressly for inclusion into FreeBSD. Other use
.\" is permitted provided this notation is included.
.\" 4. Absolutely no warranty of function or purpose is made by the author
.\" David Nugent.
.\" 5. Modifications may be freely made to this file providing the above
.\" conditions are met.
.\"
.\" $FreeBSD$
.\"
.Dd January 23, 2011
.Dt LIMITS 1
.Os
.Sh NAME
.Nm limits
.Nd set or display process resource limits
.Sh SYNOPSIS
.Nm
.Op Fl C Ar class | Fl P Ar pid | Fl U Ar user
.Op Fl SHB
.Op Fl ea
.Op Fl bcdflmnstuvpw Op Ar val
.Nm
.Op Fl C Ar class | Fl U Ar user
.Op Fl SHB
.Op Fl bcdflmnstuvpw Op Ar val
.Op Fl E
.Oo
.Op Ar name Ns = Ns Ar value ...
.Ar command
.Oc
.Sh DESCRIPTION
The
.Nm
utility either prints or sets kernel resource limits, and may optionally set
environment variables like
.Xr env 1
and run a program with the selected resources.
Three uses of the
.Nm
utility are possible:
.Bl -tag -width indent
.It Xo
.Nm
.Op Ar limitflags
.Op Ar name Ns = Ns Ar value ...
.Ar command
.Xc
This usage sets limits according to
.Ar limitflags ,
optionally sets environment variables given as
.Ar name Ns = Ns Ar value
pairs, and then runs the specified
.Ar command .
.It Nm Op Ar limitflags
This usage determines values of resource settings according to
.Ar limitflags ,
does not attempt to set them and outputs these values to
standard output.
By default, this will output the current kernel resource settings
active for the calling process.
Using the
.Fl C Ar class
or
.Fl U Ar user
options, you may also display the current resource settings modified
by the appropriate login class resource limit entries from
the
.Xr login.conf 5
login capabilities database.
.It Nm Fl e Op Ar limitflags
This usage determines values of resource settings according to
.Ar limitflags ,
but does not set them itself.
Like the previous usage, it outputs these values to standard
output, except that it will emit them in
.Ic eval
format, suitable for the calling shell.
The calling shell is determined by examining the entries in the
.Pa /proc
file system for the parent process.
If the shell is known (i.e., it is one of
.Nm sh , csh , bash , tcsh , ksh , pdksh
or
.Nm rc ) ,
.Nm
emits
.Ic limit
or
.Ic ulimit
commands in the format understood by
that shell.
If the name of the shell cannot be determined, then the
.Ic ulimit
format used by
.Xr sh 1
is used.
.Pp
This is very useful for setting limits used by scripts, or prior
launching of daemons and other background tasks with specific
resource limit settings, and provides the benefit of allowing
global configuration of maximum resource usage by maintaining a
central database of settings in the login class database.
.Pp
Within a shell script,
.Nm
will normally be used with eval within backticks as follows:
.Pp
.Dl "eval `limits -e -C daemon`"
.Pp
which causes the output of
.Nm
to be evaluated and set by the current shell.
.El
.Pp
The value of
.Ar limitflags
specified in the above contains one or more of the following options:
.Bl -tag -width ".Fl C Ar class"
.It Fl C Ar class
Use current resource values, modified by the resource entries applicable
for the login class
.Ar class .
.It Fl U Ar user
Use current resource values, modified by the resource entries applicable
to the login class the
.Ar user
belongs to.
If user does not belong to any class, then the resource capabilities
for the
.Dq Li default
class are used, if it exists, or the
.Dq Li root
class if the user is a superuser account.
.It Fl P Ar pid
Select or set limits for the process identified by the
.Ar pid .
.It Fl S
Select display or setting of
.Dq soft
(or current) resource limits.
If specific limits settings follow this switch, only soft limits are
affected unless overridden later with either the
.Fl H
or
.Fl B
options.
.It Fl H
Select display or setting of
.Dq hard
(or maximum) resource limits.
If specific limits settings follow this switch, only hard limits are
affected until overridden later with either the
.Fl S
or
.Fl B
options.
.It Fl B
Select display or setting of both
.Dq soft
(current) or
.Dq hard
(maximum)
resource limits.
If specific limits settings follow this switch, both soft and hard
limits are affected until overridden later with either the
.Fl S
or
.Fl H
options.
.Fl e
Select
.Dq "eval mode"
formatting for output.
This is valid only on display mode and cannot be used when running a
command.
The exact syntax used for output depends upon the type of shell from
which
.Nm
is invoked.
.It Fl b Op Ar val
Select or set the
.Va sbsize
resource limit.
.It Fl c Op Ar val
Select or set (if
.Ar val
is specified) the
.Va coredumpsize
resource limit.
A value of 0 disables core dumps.
.It Fl d Op Ar val
Select or set (if
.Ar val
is specified) the
.Va datasize
resource limit.
.It Fl f Op Ar val
Select or set the
.Va filesize
resource limit.
.It Fl l Op Ar val
Select or set the
.Va memorylocked
resource limit.
.It Fl m Op Ar val
Select or set the
.Va memoryuse
size limit.
.It Fl n Op Ar val
Select or set the
.Va openfiles
resource limit.
The system-wide limit on the maximum number of
open files per process can be viewed by examining the
.Va kern.maxfilesperproc
.Xr sysctl 8
variable.
The total number of simultaneously open files in the entire
system is limited to the value displayed by the
.Va kern.maxfiles
.Xr sysctl 8
variable.
.It Fl s Op Ar val
Select or set the
.Va stacksize
resource limit.
.It Fl t Op Ar val
Select or set the
.Va cputime
resource limit.
.It Fl u Op Ar val
Select or set the
.Va maxproc
resource limit.
The system-wide limit on the maximum number of processes
allowed per UID can be viewed by examining the
.Va kern.maxprocperuid
.Xr sysctl 8
variable.
The maximum number of processes that can be running simultaneously
in the entire system is limited to the value of the
.Va kern.maxproc
.Xr sysctl 8
variable.
.It Fl v Op Ar val
Select or set the
.Va virtualmem
resource limit.
This limit encompasses the entire VM space for the user process
and is inclusive of text, data, bss, stack,
.Xr brk 2 ,
.Xr sbrk 2
and
.Xr mmap 2 Ns 'd
space.
.It Fl p Op Ar val
Select or set the
.Va pseudoterminals
resource limit.
.It Fl w Op Ar val
Select or set the
.Va swapuse
resource limit.
.El
.Pp
Valid values for
.Ar val
in the above set of options consist of either the
string
.Dq Li infinity ,
.Dq Li inf ,
.Dq Li unlimited
or
.Dq Li unlimit
for an infinite (or kernel-defined maximum)
limit, or a numeric value optionally followed by a suffix.
Values which relate to size default to a value in bytes, or one of the
following suffixes may be used as a multiplier:
.Pp
.Bl -tag -offset indent -width 4n -compact
.It Li b
512 byte blocks.
.It Li k
kilobytes (1024 bytes).
.It Li m
megabytes (1024*1024 bytes).
.It Li g
gigabytes.
.It Li t
terabytes.
.El
.Pp
The
.Va cputime
resource defaults to a number of seconds, but a multiplier may be
used, and as with size values, multiple values separated by a valid
suffix are added together:
.Pp
.Bl -tag -offset indent -width 4n -compact
.It Li s
seconds.
.It Li m
minutes.
.It Li h
hours.
.It Li d
days.
.It Li w
weeks.
.It Li y
365 day years.
.El
.Bl -tag -width ".Fl C Ar class"
.It Fl E
Cause
.Nm
to completely ignore the environment it inherits.
.It Fl a
Force all resource settings to be displayed even if
other specific resource settings have been specified.
For example, if you wish to disable core dumps when starting up
the Usenet News system, but wish to set all other resource settings
as well that apply to the
.Dq Li news
account, you might use:
.Pp
.Dl "eval `limits -U news -aBec 0`"
.Pp
As with the
.Xr setrlimit 2
call, only the superuser may raise process
.Dq hard
resource limits.
Non-root users may, however, lower them or change
.Dq soft
resource limits
within to any value below the hard limit.
When invoked to execute a program, the failure of
.Nm
to raise a hard limit is considered a fatal error.
.El
.Sh EXIT STATUS
The
.Nm
utility
exits with
.Dv EXIT_FAILURE
if usage is incorrect in any way; i.e., an invalid
option, or set/display options are selected in the same invocation,
.Fl e
is used when running a program, etc.
When run in display or eval mode,
.Nm
exits with a status of
.Dv EXIT_SUCCESS .
When run in command mode and execution of the command succeeds, the exit status
will be whatever the executed program returns.
.Sh SEE ALSO
.Xr csh 1 ,
.Xr env 1 ,
.Xr limit 1 ,
.Xr sh 1 ,
.Xr getrlimit 2 ,
.Xr setrlimit 2 ,
.Xr login_cap 3 ,
.Xr login.conf 5 ,
.Xr rctl 8 ,
.Xr sysctl 8
.Sh BUGS
The
.Nm
utility does not handle commands with equal
.Pq Ql =
signs in their
names, for obvious reasons.
.Pp
When eval output is selected, the
.Pa /proc
file system must be installed
and mounted for the shell to be correctly determined, and therefore
output syntax correct for the running shell.
The default output is valid for
.Xr sh 1 ,
so this means that any
usage of
.Nm
in eval mode prior mounting
.Pa /proc
may only occur in standard bourne
shell scripts.
.Pp
The
.Nm
utility makes no effort to ensure that resource settings emitted or displayed
are valid and settable by the current user.
Only a superuser account may raise hard limits, and when doing so
the
.Fx
kernel will silently lower limits to values less than
specified if the values given are too high.
|