1.\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, is permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice immediately at the beginning of the file, without modification, 9.\" this list of conditions, and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 3. This work was done expressly for inclusion into FreeBSD. Other use 14.\" is permitted provided this notation is included. 15.\" 4. Absolutely no warranty of function or purpose is made by the author 16.\" David Nugent. 17.\" 5. Modifications may be freely made to this file providing the above 18.\" conditions are met. 19.\" 20.\" $FreeBSD$ 21.\" 22.Dd January 15, 1996 23.Dt LIMITS 1 24.Os FreeBSD 25.Sh NAME 26.Nm limits 27.Nd set or display process resource limits 28.Sh SYNOPSIS 29.Nm limits 30.Op Fl C Ar class 31.Op Fl SHB 32.Op Fl ea 33.Op Fl cdflmnstu Op val 34.Nm limits 35.Op Fl C Ar class 36.Op Fl SHB 37.Op Fl cdflmnstu Op val 38.Op Fl E 39.Op Ar name=value ... 40.Op Ar command 41.Nm limits 42.Op Fl U Ar user 43.Op Fl SHB 44.Op Fl ea 45.Op Fl cdflmnstu Op val 46.Nm limits 47.Op Fl U Ar user 48.Op Fl SHB 49.Op Fl cdflmnstu Op val 50.Op Fl E 51.Op Ar name=value ... 52.Op Ar command 53.Sh DESCRIPTION 54.Nm Limits 55either prints or sets kernel resource limits, and may optionally set 56environment variables like 57.Xr env 1 58and run a program with the selected resources. 59Three uses of the 60.Nm limits 61command are possible: 62.Pp 63.Bl -hang -width indent 64.It Nm limits Op Ar limitflags 65.Op Ar name=value 66.Ar command 67.Pp 68This usage sets limits according to 69.Ar limitflags , 70optionally sets environment variables given as 71.Ar name=value 72pairs, and then runs the specified command. 73.It Nm limits Op Ar limitflags 74.Pp 75This usage determines values of resource settings according to 76.Ar limitflags , 77does not attempt to set them and outputs these values to 78standard output. 79By default, this will output the current kernel resource settings 80active for the calling process. 81Using the 82.Fl C Ar class 83or 84.Fl U Ar user 85flags, you may also display the current resource settings modified 86by the the appropriate login class resource limit entries from 87the 88.Xr login.conf 5 89login capabilities database. 90.It Nm limits Fl e Op Ar limitflags 91.Pp 92This usage determines values of resource settings according to 93.Ar limitflags , 94but does not set them itself. 95Like the previous usage it outputs these values to standard 96output, except that it will emit them in 97.Em eval 98format, suitable for the calling shell. 99The calling shell is determined by examining the entries in the 100.Pa /proc 101filesystem for the parent process. 102If the shell is known (ie. it is one of sh, csh, bash, tcsh, ksh, 103pdksh or rc), 104.Nm limits 105emits 'limit' or 'ulimit' commands in the format understood by 106that shell. 107If the name of the shell cannot be determined, then the 'ulimit' 108format used by 109.Pa /bin/sh 110is used. 111.Pp 112This is very useful for setting limits used by scripts, or prior 113launching of daemons and other background tasks with specific 114resource limit settings, and provides the benefit of allowing 115global configuration of maximum resource usage by maintaining a 116central database of settings in the login class database. 117.Pp 118Within a shell script, 119.Nm limits 120will normally be used with eval within backticks as follows: 121.Pp 122.Dl eval `limits -e -C daemon` 123.Pp 124which causes the output of 125.Nm limits 126to be evaluated and set by the current shell. 127.El 128.Pp 129The value of limitflags specified in the above contains one or more of the 130following options: 131.Pp 132.Bl -tag -width "-d [limit]" 133.It Fl C Ar class 134Use current resource values, modified by the resource entries applicable 135for the login class "class". 136.It Fl U Ar user 137Use current resource values, modified by the resource entries applicable 138to the login class which "user" belongs to. 139If the user does not belong to a class, then the resource capabilities 140for the "default" class are used, if it exists, or the "root" class if 141the user is a superuser account. 142.It Fl S 143Selects display or setting of "soft" (or current) resource limits. 144If specific limits settings follow this switch, only soft limits are 145affected unless overridden later with either the 146.Fl H 147or 148.Fl B 149flags. 150.It Fl H 151Selects display or setting of "hard" (or maximum) resource limits. 152If specific limits settings follow this switch, only hard limits are 153affected until overridden later with either the 154.Fl S 155or 156.Fl B 157flags. 158.It Fl B 159Selects display or setting of both "soft" (current) or "hard" (maximum) 160resource limits. 161If specific limits settings follow this switch, both soft and hard 162limits are affected until overridden later with either the 163.Fl S 164or 165.Fl H 166flags. 167.Fl e 168Selects "eval mode" formatting for output. 169This is valid only on display mode and cannot be used when running a 170command. 171The exact syntax used for output depends upon the type of shell from 172which 173.Nm limits 174is invoked. 175.It Fl b Op Ar limit 176Selects or sets the 177.Em sbsize 178resource limit. 179.It Fl c Op Ar limit 180Selects or sets (if 'limit' is specified) the 181.Em coredumpsize 182resource limit. 183A value of 0 disables core dumps. 184.It Fl d Op Ar limit 185Selects or sets (if 'limit' is specified) the 186.Em datasize 187resource limit. 188.It Fl f Op Ar limit 189Selects or sets the 190.Em filesize 191resource limit. 192.It Fl l Op Ar limit 193Selects or sets the 194.Em memorylocked 195resource limit. 196.It Fl m Op Ar limit 197Selects or sets the 198.Em memoryuse 199size limit. 200.It Fl n Op Ar limit 201Selects or sets the 202.Em openfiles 203resource limit. The system-wide limit on the maximum number of 204open files per process can be viewed using the 'sysctl kern.maxfilesperproc' 205command. The total number of simultaneously open files in the entire 206system is limited to the value displayed by the 'sysctl kern.maxfiles' 207command. 208.It Fl s Op Ar limit 209Selects or sets the 210.Em stacksize 211resource limit. 212.It Fl t Op Ar limit 213Selects or sets the 214.Em cputime 215resource limit. 216.It Fl u Op Ar limit 217Selects or sets the 218.Em maxproc 219resource limit. The system-wide limit on the maximum number of processes 220allowed per UID can be viewed using the 'sysctl kern.maxprocperuid' command. 221The maximum number of processes that can be running simultaneously 222in the entire system is limited to the value given by 223the 'sysctl kern.maxproc' command. 224.Pp 225Valid values for 'limit' in the above set of flags consist of either the 226string 'infinity' or 'inf' for an infinite (or kernel-defined maximum) 227limit, or a numeric value maybe followed by a suffix. 228Values which relate to size default to a value in bytes, or one of the 229following suffixes may be used as a multiplier: 230.Pp 231.Bl -tag -offset indent -width "xxxx" -compact 232.It b 233512 byte blocks. 234.It k 235kilobytes (1024 bytes). 236.It m 237megabytes (1024*1024 bytes). 238.It g 239gigabytes. 240.It t 241terabytes. 242.El 243.Pp 244The 245.Em cputime 246resource defaults to a number of seconds, but a multiplier may be 247used, and as with size values, multiple values separated by a valid 248suffix are added together: 249.Bl -tag -offset indent -width "xxxx" -compact 250.It s 251seconds. 252.It m 253minutes. 254.It h 255hours. 256.It d 257days. 258.It w 259weeks. 260.It y 261365 day years. 262.El 263.Pp 264.It Fl E 265The option 266.Sq Fl E 267causes 268.Nm limits 269to completely ignore the environment it inherits. 270.It Fl a 271This option forces all resource settings to be displayed even if 272other specific resource settings have been specified. 273For example, if you wish to disable core dumps when starting up 274the usenet news system, but wish to set all other resource settings 275as well that apply to the 'news' account, you might use: 276.Pp 277.Dl eval `limits -U news -aBec 0` 278.Pp 279As with the 280.Xr setrlimit 2 281call, only the superuser may raise process "hard" resource limits. 282Non-root users may, however, lower them or change "soft" resource limits 283within to any value below the hard limit. 284When invoked to execute a program, the failure of 285.Nm limits 286to raise a hard limit is considered a fatal error. 287.El 288.Sh DIAGNOSTICS 289.Nm Limits 290exits with EXIT_FAILURE if usage is incorrect in any way; ie. an invalid 291option, or set/display options are selected in the same invocation, 292.Fl e 293is used when running a program, etc. 294When run in display or eval mode, 295.Nm limits 296exits with a status of EXIT_SUCCESS. 297When run in command mode and execution of the command succeeds, the exit status 298will be whatever the executed program returns. 299.Sh SEE ALSO 300.Xr csh 1 , 301.Xr env 1 , 302.Xr limit 1 , 303.Xr sh 1 , 304.Xr getrlimit 2 , 305.Xr setrlimit 2 , 306.Xr login_cap 3 , 307.Xr login.conf 5 , 308.Xr sysctl 8 309.Sh BUGS 310.Nm Limits 311does not handle commands with equal (``='') signs in their 312names, for obvious reasons. 313.Pp 314When eval output is selected, the /proc filesystem must be installed 315and mounted for the shell to be correctly determined, and therefore 316output syntax correct for the running shell. 317The default output is valid for /bin/sh, so this means that any 318usage of 319.Nm limits 320in eval mode prior mounting /proc may only occur in standard bourne 321shell scripts. 322.Pp 323.Nm Limits 324makes no effort to ensure that resource settings emitted or displayed 325are valid and settable by the current user. 326Only a superuser account may raise hard limits, and when doing so 327the FreeBSD kernel will silently lower limits to values less than 328specified if the values given are too high. 329