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savecore(1M)							  savecore(1M)

NAME    [Toc]    [Back]

     savecore -	save a crash vmcore dump of the	operating system

SYNOPSIS    [Toc]    [Back]

     /etc/savecore [ -f	] [ -v ] [ -d dumpdev ]	dirname	[ system ]

DESCRIPTION    [Toc]    [Back]

     savecore is meant to be called by /etc/rc2.d/S48savecore.	savecore
     attempts to save the core dump of the system (assuming one	was made) and
     write a reboot message in the shutdown log.  The S48savecore script will
     save all output files to dirname, which defaults to /var/adm/crash,
     unless overridden by site-specific	command-line options in	the file

     In	the event of a software-detectable system crash, one of	the last steps
     that the kernel performs before shutting down is to write the contents of
     system memory to the dump device.	There are several ways in which	this
     information can be	used to	determine the cause and	solution to the	crash.

     The dump device normally defaults to /dev/swap.  The process of creating
     the dump image will overwrite any data on the dump	device.	 Thus, the
     dump device must be a raw partition that does not contain any data	that
     needs to be preserved across a system crash (which	is why /dev/swap is
     the obvious candidate for the dump	device).  As each page of memory is
     written to	the dump device, it is compressed in order to save disk	space.

     On	reboot,	the S48savecore	script initially checks	the value of the
     savecore chkconfig(1M) option.  By	default, this option is	on for all
     systems.  If it is	turned off, icrash(1M) will run	against	the compressed
     core image	on the dump device and write reports about the system crash to
     dirname.  The compressed core image on the	dump device will not be	saved
     to	disk.

     If	the savecore chkconfig(1M) option is left on, savecore will read the
     compressed	core image saved on the	dump device and	write it to the	file
     dirname/vmcore.N.comp.  This core file can	then be	uncompressed using the
     uncompvm(1M) command, although most utilities designed to look at system
     core files	do not require that the	core file be uncompressed.  The	core
     file also has a header which contains certain information about the
     system crash.  This information can be retrieved by running uncompvm(1M)
     with the -h option.

     Making sense of any saved core image requires the symbol table of the
     operating system that was running at the time of the crash.  For that
     reason, if	the savecore chkconfig(1M) option is on	when the S48savecore
     script runs, savecore will	save the current default kernel	boot file
     /unix as dirname/unix.N.  Otherwise, /unix	will not be copied to dirname.
     The trailing .N in	the pathname is	replaced by a number stored in the
     dirname/bounds file that grows every time savecore	is run in that

									Page 1

savecore(1M)							  savecore(1M)

     Before savecore writes out	a core image, it reads a number	from the file
     dirname/minfree.  If the number of	free bytes on the filesystem that
     contains dirname is less than the number obtained from the	minfree	file,
     the core dump is not saved.  If the minfree file does not exist, savecore
     always writes out the core	file (assuming that a core dump	was taken).

     savecore also logs	a reboot message using facility	LOG_AUTH (see
     syslog(3C)).  If the system crashed as a result of	a panic, savecore logs
     the panic string also.

     savecore assumes that /unix corresponds to	the running system at the time
     of	the crash.  If the core	dump was from a	system other than /unix, the
     name of that system must be supplied as system.

     The following options apply to savecore:

     -f	  Ordinarily, savecore checks a	magic number on	the dump device
	  (usually /dev/swap) to determine if a	core dump was made.  This flag
	  forces savecore to attempt to	save the core image regardless of the
	  state	of this	magic number.  This may	be necessary since savecore
	  always clears	the magic number after reading it.  If a previous
	  attempt to save the image failed in some manner, it is still
	  possible to restart the save with this option.

     -v	  Give more verbose output.

     -d	  Specifies the	source device to check for a dump. It should be	in the
	  form of dksXdYsZ where X is the controller number, Y the disk	device
	  and Z	the the	partition (example: dks0d2s1). The normal default is


     The S48savecore script creates a number of	diagnostics files:

     analysis.N	  This file contains a report that has information specific to
		  the system crash.  It	is created by icrash(1M) and contains
		  either an ICRASH CORE	FILE REPORT, or	a copy of the core
		  dump header.

VMCORE CONTENTS    [Toc]    [Back]

     The size of the swap space	is limited, and	often smaller than the system
     physical memory size, so a	dump is	likely to be partial.  For this
     reason, the kernel	takes steps to squeeze as much information as possible
     into the available	space.

     The kernel	uses run-length	encoding to compress memory pages as it	stores
     them.  This lessens the impact of pages that contain mostly zeroes.

     The kernel	first stores the putbuf, which contains	the system crash
     messages, followed	by all memory in use by	the operating system, followed
     by	all memory in use by user processes, and finally all of	the rest of
     free memory.  The putbuf and operating system memory contain the most

									Page 2

savecore(1M)							  savecore(1M)

     important information and will generally fit in their entirety.

     The systune(1M) variable dump_level controls the data dumped in a system
     crash, and	may have the following values:

     4 dump putbuf, kernel, buffer cache, user,	and free pages
	   (usual setting)

     3 dump putbuf, kernel, buffer cache, and user pages

     2 dump putbuf, kernel, and	buffer cache pages

     1 dump putbuf and kernel pages

     0 dump putbuf only

DIAGNOSTICS    [Toc]    [Back]

     warning: /unix may	not have created core file
	  Printed if savecore believes that the	system core file does not
	  correspond with the /unix operating system binary.

     savecore: /unix is	not the	running	system
	  Printed for the obvious reason.  If the system that crashed was
	  /unix, use mv(1) to change its name before running savecore.	Use
	  mv(1)	or ln(1) to rename or produce a	link to	the name of the	file
	  of the currently running operating system binary.  This enables
	  savecore to find name	list information about the current state of
	  the running system from the file /unix.

FILES    [Toc]    [Back]

     /unix			    current IRIX
     /var/adm/crash		    default place to create dump files
     /var/adm/crash/bounds	    number for next dump file
     /var/adm/crash/minfree	    minimum filesystem free space
     /var/adm/crash/analysis.N	    file created by icrash(1M) that contains
				    information	about the core dump
     /etc/config/savecore.options   site-specific command-line options

SEE ALSO    [Toc]    [Back]

     uncompvm(1M), trcore(1M), nlist(3X), icrash(1M), chkconfig(1M).

									PPPPaaaaggggeeee 3333
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 Similar pages
Name OS Title
trcore IRIX truncate a crash vmcore dump of the operating system
savecrash HP-UX save a crash dump of the operating system
uncompvm IRIX expand a compressed IRIX vmcore dump of the operating system
savecore FreeBSD save a core dump of the operating system
savecore OpenBSD save a core dump of the operating system
cr_read HP-UX read from crash dump
kvm_dump_inval NetBSD crash-dump support functions
cr_close HP-UX close a crash dump descriptor
crashutil HP-UX manipulate crash dump data
cr_info HP-UX retrieve crash dump information
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