.\" Copyright (c) 1996 David Nugent .\" 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. .\" .\" $Id: limits.1,v 1.10 1999/03/15 15:36:56 ghelmer Exp $ .\" .Dd January 15, 1996 .Dt LIMITS 1 .Os FreeBSD .Sh NAME .Nm limits .Nd set or display process resource limits .Sh SYNOPSIS .Nm limits .Op Fl C Ar class .Op Fl SHB .Op Fl ea .Op Fl cdflmnstu Op val .Nm limits .Op Fl C Ar class .Op Fl SHB .Op Fl cdflmnstu Op val .Op Fl E .Op Ar name=value ... .Op Ar command .Nm limits .Op Fl U Ar user .Op Fl SHB .Op Fl ea .Op Fl cdflmnstu Op val .Nm limits .Op Fl U Ar user .Op Fl SHB .Op Fl cdflmnstu Op val .Op Fl E .Op Ar name=value ... .Op Ar command .Sh DESCRIPTION .Nm Limits 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 limits command are possible: .Pp .Bl -hang -width indent .It Nm limits Op Ar limitflags .Op Ar name=value .Ar command .Pp This usage sets limits according to .Ar limitflags , optionally sets environment variables given as .Ar name=value pairs, and then runs the specified command. .It Nm limits Op Ar limitflags .Pp 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 flags, you may also display the current resource settings modified by the the appropriate login class resource limit entries from the .Xr login.conf 5 login capabilities database. .It Nm limits Fl e Op Ar limitflags .Pp 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 .Em eval format, suitable for the calling shell. The calling shell is determined by examining the entries in the .Pa /proc filesystem for the parent process. If the shell is known (ie. it is one of sh, csh, bash, tcsh, ksh, pdksh or rc), .Nm limits emits 'limit' or 'ulimit' commands in the format understood by that shell. If the name of the shell cannot be determined, then the 'ulimit' format used by .Pa /bin/sh 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 limits will normally be used with eval within backticks as follows: .Pp .Dl eval `limits -e -C daemon` .Pp which causes the output of .Nm limits to be evaluated and set by the current shell. .El .Pp The value of limitflags specified in the above contains one or more of the following options: .Pp .Bl -tag -width "-d [limit]" .It Fl C Ar class Use current resource values, modified by the resource entries applicable for the login class "class". .It Fl U Ar user Use current resource values, modified by the resource entries applicable to the login class which "user" belongs to. If the user does not belong to a class, then the resource capabilities for the "default" class are used, if it exists, or the "root" class if the user is a superuser account. .It Fl S Selects display or setting of "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 flags. .It Fl H Selects display or setting of "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 flags. .It Fl B Selects display or setting of both "soft" (current) or "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 flags. .Fl e Selects "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 limits is invoked. .It Fl c Op Ar limit Selects or sets (if 'limit' is specified) the .Em coredumpsize resource limit. A value of 0 disables core dumps. .It Fl d Op Ar limit Selects or sets (if 'limit' is specified) the .Em datasize resource limit. .It Fl f Op Ar limit Selects or sets the .Em filesize resource limit. .It Fl l Op Ar limit Selects or sets the .Em memorylocked resource limit. .It Fl m Op Ar limit Selects or sets the .Em memoryuse size limit. .It Fl n Op Ar limit Selects or sets the .Em openfiles resource limit. The system-wide limit on the maximum number of open files per process can be viewed using the 'sysctl kern.maxfilesperproc' command. The total number of simultaneously open files in the entire system is limited to the value displayed by the 'sysctl kern.maxfiles' command. .It Fl s Op Ar limit Selects or sets the .Em stacksize resource limit. .It Fl t Op Ar limit Selects or sets the .Em cputime resource limit. .It Fl u Op Ar limit Selects or sets the .Em maxproc resource limit. The system-wide limit on the maximum number of processes allowed per UID can be viewed using the 'sysctl kern.maxprocperuid' command. The maximum number of processes that can be running simultaneously in the entire system is limited to the value given by the 'sysctl kern.maxproc' command. .Pp Valid values for 'limit' in the above set of flags consist of either the string 'infinity' or 'inf' for an infinite (or kernel-defined maximum) limit, or a numeric value maybe 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 "xxxx" -compact .It b 512 byte blocks. .It k kilobytes (1024 bytes). .It m megabytes (1024*1024 bytes). .It g gigabytes. .It t terabytes. .El .Pp The .Em 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: .Bl -tag -offset indent -width "xxxx" -compact .It s seconds. .It m minutes. .It h hours. .It d days. .It w weeks. .It y 365 day years. .El .Pp .It Fl E The option .Sq Fl E causes .Nm limits to completely ignore the environment it inherits. .It Fl a This option forces 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 'news' account, you might use: .Pp .Dl eval `limits -U news -aBec 0` .Pp As with the .Xr setrlimit 3 call, only the superuser may raise process "hard" resource limits. Non-root users may, however, lower them or change "soft" resource limits within to any value below the hard limit. When invoked to execute a program, the failure of .Nm limits to raise a hard limit is considered a fatal error. .El .Sh DIAGNOSTICS .Nm Limits exits with EXIT_FAILURE if usage is incorrect in any way; ie. 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 limits exits with a status of 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 sysctl 8 .Sh BUGS .Nm Limits does not handle commands with equal (``='') signs in their names, for obvious reasons. .Pp When eval output is selected, the /proc filesystem 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 /bin/sh, so this means that any usage of .Nm limits in eval mode prior mounting /proc may only occur in standard bourne shell scripts. .Pp .Nm Limits 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 FreeBSD kernel will silently lower limits to values less than specified if the values given are too high.