356 lines
9.2 KiB
Groff
356 lines
9.2 KiB
Groff
.\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, is permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice immediately at the beginning of the file, without modification,
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.\" this list of conditions, and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. This work was done expressly for inclusion into FreeBSD. Other use
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.\" is permitted provided this notation is included.
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.\" 4. Absolutely no warranty of function or purpose is made by the author
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.\" David Nugent.
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.\" 5. Modifications may be freely made to this file providing the above
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.\" conditions are met.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd January 15, 1996
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.Dt LIMITS 1
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.Os
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.Sh NAME
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.Nm limits
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.Nd set or display process resource limits
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.Sh SYNOPSIS
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.Nm
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.Op Fl C Ar class
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.Op Fl SHB
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.Op Fl ea
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.Op Fl cdflmnstu Op val
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.Nm
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.Op Fl C Ar class
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.Op Fl SHB
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.Op Fl cdflmnstu Op val
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.Op Fl E
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.Op Ar name Ns = Ns Ar value ...
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.Op Ar command
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.Nm
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.Op Fl U Ar user
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.Op Fl SHB
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.Op Fl ea
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.Op Fl cdflmnstu Op val
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.Nm
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.Op Fl U Ar user
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.Op Fl SHB
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.Op Fl cdflmnstu Op val
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.Op Fl E
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.Op Ar name Ns = Ns Ar value ...
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.Op Ar command
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.Sh DESCRIPTION
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The
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.Nm
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utility either prints or sets kernel resource limits, and may optionally set
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environment variables like
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.Xr env 1
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and run a program with the selected resources.
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Three uses of the
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.Nm
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command are possible:
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.Pp
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.Bl -tag -width indent
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.It Xo
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.Nm
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.Op Ar limitflags
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.Op Ar name Ns = Ns Ar value
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.Ar command
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.Xc
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This usage sets limits according to
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.Ar limitflags ,
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optionally sets environment variables given as
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.Ar name Ns = Ns Ar value
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pairs, and then runs the specified command.
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.It Xo
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.Nm
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.Op Ar limitflags
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.Xc
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This usage determines values of resource settings according to
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.Ar limitflags ,
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does not attempt to set them and outputs these values to
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standard output.
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By default, this will output the current kernel resource settings
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active for the calling process.
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Using the
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.Fl C Ar class
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or
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.Fl U Ar user
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flags, you may also display the current resource settings modified
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by the appropriate login class resource limit entries from
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the
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.Xr login.conf 5
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login capabilities database.
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.It Xo
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.Nm
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.Fl e Op Ar limitflags
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.Xc
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This usage determines values of resource settings according to
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.Ar limitflags ,
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but does not set them itself.
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Like the previous usage it outputs these values to standard
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output, except that it will emit them in
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.Em eval
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format, suitable for the calling shell.
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The calling shell is determined by examining the entries in the
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.Pa /proc
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filesystem for the parent process.
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If the shell is known (i.e. it is one of sh, csh, bash, tcsh, ksh,
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pdksh or rc),
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.Nm
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emits 'limit' or 'ulimit' commands in the format understood by
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that shell.
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If the name of the shell cannot be determined, then the 'ulimit'
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format used by
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.Xr sh 1
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is used.
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.Pp
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This is very useful for setting limits used by scripts, or prior
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launching of daemons and other background tasks with specific
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resource limit settings, and provides the benefit of allowing
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global configuration of maximum resource usage by maintaining a
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central database of settings in the login class database.
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.Pp
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Within a shell script,
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.Nm
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will normally be used with eval within backticks as follows:
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.Pp
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.Dl eval `limits -e -C daemon`
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.Pp
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which causes the output of
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.Nm
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to be evaluated and set by the current shell.
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.El
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.Pp
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The value of limitflags specified in the above contains one or more of the
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following options:
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.Pp
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.Bl -tag -width "-d [limit]"
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.It Fl C Ar class
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Use current resource values, modified by the resource entries applicable
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for the login class "class".
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.It Fl U Ar user
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Use current resource values, modified by the resource entries applicable
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to the login class which "user" belongs to.
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If the user does not belong to a class, then the resource capabilities
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for the "default" class are used, if it exists, or the "root" class if
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the user is a superuser account.
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.It Fl S
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Select display or setting of "soft" (or current) resource limits.
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If specific limits settings follow this switch, only soft limits are
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affected unless overridden later with either the
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.Fl H
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or
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.Fl B
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flags.
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.It Fl H
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Select display or setting of "hard" (or maximum) resource limits.
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If specific limits settings follow this switch, only hard limits are
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affected until overridden later with either the
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.Fl S
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or
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.Fl B
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flags.
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.It Fl B
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Select display or setting of both "soft" (current) or "hard" (maximum)
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resource limits.
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If specific limits settings follow this switch, both soft and hard
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limits are affected until overridden later with either the
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.Fl S
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or
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.Fl H
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flags.
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.Fl e
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Select "eval mode" formatting for output.
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This is valid only on display mode and cannot be used when running a
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command.
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The exact syntax used for output depends upon the type of shell from
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which
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.Nm
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is invoked.
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.It Fl b Op Ar limit
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Selects or sets the
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.Em sbsize
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resource limit.
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.It Fl c Op Ar limit
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Select or set (if 'limit' is specified) the
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.Em coredumpsize
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resource limit.
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A value of 0 disables core dumps.
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.It Fl d Op Ar limit
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Select or set (if 'limit' is specified) the
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.Em datasize
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resource limit.
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.It Fl f Op Ar limit
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Select or set the
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.Em filesize
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resource limit.
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.It Fl l Op Ar limit
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Select or set the
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.Em memorylocked
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resource limit.
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.It Fl m Op Ar limit
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Select or set the
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.Em memoryuse
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size limit.
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.It Fl n Op Ar limit
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Select or set the
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.Em openfiles
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resource limit. The system-wide limit on the maximum number of
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open files per process can be viewed using the 'sysctl kern.maxfilesperproc'
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command. The total number of simultaneously open files in the entire
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system is limited to the value displayed by the 'sysctl kern.maxfiles'
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command.
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.It Fl s Op Ar limit
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Select or set the
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.Em stacksize
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resource limit.
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.It Fl t Op Ar limit
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Select or set the
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.Em cputime
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resource limit.
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.It Fl u Op Ar limit
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Select or set the
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.Em maxproc
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resource limit. The system-wide limit on the maximum number of processes
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allowed per UID can be viewed using the 'sysctl kern.maxprocperuid' command.
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The maximum number of processes that can be running simultaneously
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in the entire system is limited to the value given by
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the 'sysctl kern.maxproc' command.
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.Pp
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Valid values for
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.Ar limit
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in the above set of flags consist of either the
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string
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.Em infinity ,
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.Em inf ,
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.Em unlimited
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or
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.Em unlimit
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for an infinite (or kernel-defined maximum)
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limit, or a numeric value maybe followed by a suffix.
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Values which relate to size default to a value in bytes, or one of the
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following suffixes may be used as a multiplier:
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.Pp
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.Bl -tag -offset indent -width "xxxx" -compact
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.It b
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512 byte blocks.
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.It k
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kilobytes (1024 bytes).
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.It m
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megabytes (1024*1024 bytes).
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.It g
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gigabytes.
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.It t
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terabytes.
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.El
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.Pp
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The
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.Em cputime
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resource defaults to a number of seconds, but a multiplier may be
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used, and as with size values, multiple values separated by a valid
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suffix are added together:
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.Bl -tag -offset indent -width "xxxx" -compact
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.It s
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seconds.
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.It m
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minutes.
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.It h
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hours.
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.It d
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days.
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.It w
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weeks.
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.It y
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365 day years.
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.El
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.Pp
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.It Fl E
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The option
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.Sq Fl E
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causes
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.Nm
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to completely ignore the environment it inherits.
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.It Fl a
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This option forces all resource settings to be displayed even if
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other specific resource settings have been specified.
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For example, if you wish to disable core dumps when starting up
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the usenet news system, but wish to set all other resource settings
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as well that apply to the 'news' account, you might use:
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.Pp
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.Dl eval `limits -U news -aBec 0`
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.Pp
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As with the
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.Xr setrlimit 2
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call, only the superuser may raise process "hard" resource limits.
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Non-root users may, however, lower them or change "soft" resource limits
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within to any value below the hard limit.
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When invoked to execute a program, the failure of
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.Nm
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to raise a hard limit is considered a fatal error.
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.El
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.Sh DIAGNOSTICS
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The
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.Nm
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utility
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exits with EXIT_FAILURE if usage is incorrect in any way; i.e. an invalid
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option, or set/display options are selected in the same invocation,
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.Fl e
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is used when running a program, etc.
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When run in display or eval mode,
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.Nm
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exits with a status of EXIT_SUCCESS.
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When run in command mode and execution of the command succeeds, the exit status
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will be whatever the executed program returns.
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.Sh SEE ALSO
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.Xr csh 1 ,
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.Xr env 1 ,
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.Xr limit 1 ,
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.Xr sh 1 ,
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.Xr getrlimit 2 ,
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.Xr setrlimit 2 ,
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.Xr login_cap 3 ,
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.Xr login.conf 5 ,
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.Xr sysctl 8
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.Sh BUGS
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The
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.Nm
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utility does not handle commands with equal (``='') signs in their
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names, for obvious reasons.
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.Pp
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When eval output is selected, the
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.Pa /proc
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filesystem must be installed
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and mounted for the shell to be correctly determined, and therefore
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output syntax correct for the running shell.
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The default output is valid for
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.Xr sh 1 ,
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so this means that any
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usage of
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.Nm
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in eval mode prior mounting
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.Pa /proc
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may only occur in standard bourne
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shell scripts.
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.Pp
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The
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.Nm
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utility makes no effort to ensure that resource settings emitted or displayed
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are valid and settable by the current user.
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Only a superuser account may raise hard limits, and when doing so
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the
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.Fx
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kernel will silently lower limits to values less than
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specified if the values given are too high.
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