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Date: Thu, 21 Mar 2013 11:33:20 GMT
From: Fabian Keil <fk@fabiankeil.de>
To: freebsd-gnats-submit@FreeBSD.org
Subject: dumpon(8) unaware of mini crash dumps
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>Number:         177188
>Category:       docs
>Synopsis:       dumpon(8) unaware of mini crash dumps
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    joel
>State:          closed
>Quarter:        
>Keywords:       
>Date-Required:  
>Class:          doc-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu Mar 21 11:40:01 UTC 2013
>Closed-Date:    Tue Apr 30 07:23:21 UTC 2013
>Last-Modified:  Tue Apr 30 07:30:00 UTC 2013
>Originator:     Fabian Keil
>Release:        HEAD
>Organization:
>Environment:
FreeBSD r500.local 10.0-CURRENT FreeBSD 10.0-CURRENT #555 r+5b01145: Wed Mar 20 22:01:58 CET 2013     fk@r500.local:/usr/obj/usr/src/sys/ZOEY  amd64

>Description:
dumpon(8) currently states:

| The dumpon utility will refuse to enable a dump device which is smaller
| than the total amount of physical memory as reported by the hw.physmem
| sysctl(8) variable.

If mini crash dumps are enabled smaller dump devices are actually accepted.

It might also be worth mentioning that with mini crash dumps disabled no error message is printed unless -v is used.

>How-To-Repeat:
fk@r500 ~ $sysctl debug.minidump
debug.minidump: 1
fk@r500 ~ $sysctl kern.shutdown.dumpdevname
kern.shutdown.dumpdevname: 
fk@r500 ~ $sysctl hw.physmem
hw.physmem: 2070306816
fk@r500 ~ $diskinfo -v /dev/da0 | grep bytes
	750780416   	# mediasize in bytes (716M)
fk@r500 ~ $sudo dumpon /dev/da0
fk@r500 ~ $echo $?
0
fk@r500 ~ $sysctl kern.shutdown.dumpdevname
kern.shutdown.dumpdevname: da0
fk@r500 ~ $sudo dumpon off
fk@r500 ~ $sudo sysctl debug.minidump=0
debug.minidump: 1 -> 0
fk@r500 ~ $sudo dumpon /dev/da0
fk@r500 ~ $echo $?
74
fk@r500 ~ $sudo dumpon -v /dev/da0
/dev/da0 is smaller than physical memory

>Fix:
Update the man page.

>Release-Note:
>Audit-Trail:
Responsible-Changed-From-To: freebsd-doc->joel 
Responsible-Changed-By: joel 
Responsible-Changed-When: Wed Apr 24 07:50:52 UTC 2013 
Responsible-Changed-Why:  
Take 

http://www.freebsd.org/cgi/query-pr.cgi?pr=177188 
State-Changed-From-To: open->closed 
State-Changed-By: joel 
State-Changed-When: Tue Apr 30 07:22:24 UTC 2013 
State-Changed-Why:  
I've updated the man page and I'm closing this PR. Thanks! 

http://www.freebsd.org/cgi/query-pr.cgi?pr=177188 

From: dfilter@FreeBSD.ORG (dfilter service)
To: bug-followup@FreeBSD.org
Cc:  
Subject: Re: docs/177188: commit references a PR
Date: Tue, 30 Apr 2013 07:22:26 +0000 (UTC)

 Author: joel (doc committer)
 Date: Tue Apr 30 07:22:03 2013
 New Revision: 250095
 URL: http://svnweb.freebsd.org/changeset/base/250095
 
 Log:
   Adapt to the fact that minidumps are now on by default.
   
   PR:		177188
 
 Modified:
   head/sbin/dumpon/dumpon.8
 
 Modified: head/sbin/dumpon/dumpon.8
 ==============================================================================
 --- head/sbin/dumpon/dumpon.8	Tue Apr 30 06:41:42 2013	(r250094)
 +++ head/sbin/dumpon/dumpon.8	Tue Apr 30 07:22:03 2013	(r250095)
 @@ -28,7 +28,7 @@
  .\"     From: @(#)swapon.8	8.1 (Berkeley) 6/5/93
  .\" $FreeBSD$
  .\"
 -.Dd May 12, 1995
 +.Dd April 29, 2013
  .Dt DUMPON 8
  .Os
  .Sh NAME
 @@ -59,14 +59,21 @@ controlled by the
  variable in the boot time configuration file
  .Pa /etc/rc.conf .
  .Pp
 -For most systems the size of the specified dump device must be at
 +The default type of kernel crash dump is the mini crash dump.
 +Mini crash dumps hold only memory pages in use by the kernel.
 +Alternatively, full memory dumps can be enabled by setting the
 +.Va debug.minidump
 +.Xr sysctl 8
 +variable to 0.
 +.Pp
 +For systems using full memory dumps, the size of the specified dump
 +device must be at
  least the size of physical memory.
  Even though an additional 64 kB header is added to the dump, the BIOS for a
  platform typically holds back some memory, so it is not usually
  necessary to size the dump device larger than the actual amount of RAM
  available in the machine.
 -.Pp
 -The
 +Also, when using full memory dumps, the
  .Nm
  utility will refuse to enable a dump device which is smaller than the
  total amount of physical memory as reported by the
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>Unformatted:
