5f23a3b5ca
After the MPSAFE TTY import we support an additional rlimit, called RLIMIT_NPTS. This limit allows you to cap the amount of pseudo-terminals allocated by one user. We forgot to add support for this limit to limits(1), which means it crashed. Add the proper bits to make it work like it should. Unfortunately not all shells actually implement the RLIMIT, so unfortunately I suspect it to be broken with certain shells. Submitted by: Yuriy Tsibizov <yuriy tsibizov gfk ru>
405 lines
9.5 KiB
Groff
405 lines
9.5 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 September 18, 2002
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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 | Fl U Ar user
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.Op Fl SHB
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.Op Fl ea
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.Op Fl bcdflmnstuvp Op Ar val
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.Nm
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.Op Fl C Ar class | Fl U Ar user
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.Op Fl SHB
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.Op Fl bcdflmnstuvp Op Ar val
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.Op Fl E
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.Oo
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.Op Ar name Ns = Ns Ar value ...
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.Ar command
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.Oc
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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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utility are possible:
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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
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.Ar command .
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.It Nm Op Ar limitflags
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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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options, 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 Nm Fl e Op Ar limitflags
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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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.Ic 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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file system for the parent process.
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If the shell is known (i.e., it is one of
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.Nm sh , csh , bash , tcsh , ksh , pdksh
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or
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.Nm rc ) ,
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.Nm
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emits
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.Ic limit
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or
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.Ic ulimit
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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
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.Ic 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
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.Ar limitflags
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specified in the above contains one or more of the following options:
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.Bl -tag -width ".Fl C Ar class"
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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
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.Ar 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 the
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.Ar user
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belongs to.
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If user does not belong to any class, then the resource capabilities
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for the
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.Dq Li default
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class are used, if it exists, or the
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.Dq Li root
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class if the user is a superuser account.
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.It Fl S
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Select display or setting of
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.Dq soft
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(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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options.
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.It Fl H
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Select display or setting of
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.Dq hard
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(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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options.
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.It Fl B
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Select display or setting of both
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.Dq soft
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(current) or
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.Dq hard
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(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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options.
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.Fl e
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Select
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.Dq "eval mode"
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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 val
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Select or set the
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.Va sbsize
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resource limit.
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.It Fl c Op Ar val
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Select or set (if
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.Ar val
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is specified) the
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.Va 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 val
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Select or set (if
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.Ar val
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is specified) the
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.Va datasize
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resource limit.
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.It Fl f Op Ar val
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Select or set the
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.Va filesize
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resource limit.
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.It Fl l Op Ar val
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Select or set the
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.Va memorylocked
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resource limit.
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.It Fl m Op Ar val
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Select or set the
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.Va memoryuse
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size limit.
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.It Fl n Op Ar val
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Select or set the
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.Va openfiles
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resource limit.
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The system-wide limit on the maximum number of
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open files per process can be viewed by examining the
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.Va kern.maxfilesperproc
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.Xr sysctl 8
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variable.
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The total number of simultaneously open files in the entire
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system is limited to the value displayed by the
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.Va kern.maxfiles
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.Xr sysctl 8
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variable.
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.It Fl s Op Ar val
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Select or set the
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.Va stacksize
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resource limit.
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.It Fl t Op Ar val
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Select or set the
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.Va cputime
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resource limit.
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.It Fl u Op Ar val
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Select or set the
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.Va maxproc
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resource limit.
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The system-wide limit on the maximum number of processes
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allowed per UID can be viewed by examining the
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.Va kern.maxprocperuid
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.Xr sysctl 8
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variable.
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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 of the
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.Va kern.maxproc
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.Xr sysctl 8
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variable.
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.It Fl v Op Ar val
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Select or set the
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.Va virtualmem
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resource limit.
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This limit encompasses the entire VM space for the user process
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and is inclusive of text, data, bss, stack,
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.Xr brk 2 ,
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.Xr sbrk 2
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and
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.Xr mmap 2 Ns 'd
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space.
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.It Fl p Op Ar val
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Select or set the
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.Va pseudoterminals
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resource limit.
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.El
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.Pp
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Valid values for
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.Ar val
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in the above set of options consist of either the
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string
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.Dq Li infinity ,
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.Dq Li inf ,
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.Dq Li unlimited
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or
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.Dq Li unlimit
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for an infinite (or kernel-defined maximum)
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limit, or a numeric value optionally 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 4n -compact
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.It Li b
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512 byte blocks.
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.It Li k
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kilobytes (1024 bytes).
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.It Li m
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megabytes (1024*1024 bytes).
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.It Li g
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gigabytes.
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.It Li 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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.Va 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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.Pp
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.Bl -tag -offset indent -width 4n -compact
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.It Li s
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seconds.
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.It Li m
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minutes.
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.It Li h
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hours.
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.It Li d
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days.
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.It Li w
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weeks.
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.It Li y
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365 day years.
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.El
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.Bl -tag -width ".Fl C Ar class"
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.It Fl E
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Cause
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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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Force 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
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.Dq Li news
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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
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.Dq hard
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resource limits.
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Non-root users may, however, lower them or change
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.Dq soft
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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 EXIT STATUS
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The
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.Nm
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utility
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exits with
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.Dv EXIT_FAILURE
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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
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.Dv 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
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.Pq Ql =
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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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file system 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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