textdump man page on FreeBSD

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TEXTDUMP(4)		 BSD Kernel Interfaces Manual		   TEXTDUMP(4)

NAME
     textdumptextdump kernel dumping facility

SYNOPSIS
     options KDB
     options DDB

DESCRIPTION
     The textdump facility allows the capture of kernel debugging information
     to disk in a human-readable rather than the machine-readable form nor‐
     mally used with kernel memory dumps and minidumps.	 This representation,
     while less complete in that it does not capture full kernel state, can
     provide debugging information in a more compact, portable, and persistent
     form than a traditional dump.  By combining textdump with other ddb(4)
     facilities, such as scripting and output capture, detailed bug informa‐
     tion can be captured in a fully automated manner.

FORMAT
     textdump data is stored in a dump partition in the same style as a regu‐
     lar memory dump, and will be automatically extracted by savecore(8) if
     present on boot.

     textdump files are stored in the tar(5) format, and consist of one or
     more text files, each storing a particular type of debugging output.  The
     following parts may be present:

     ddb.txt	  Captured ddb(4) output, if the capture facility has been
		  used.	 May be disabled by clearing the
		  debug.ddb.textdump.do_ddb sysctl.

     config.txt	  Kernel configuration, if has been compiled into the kernel.
		  May be disabled by clearing the debug.ddb.textdump.do_config
		  sysctl.

     msgbuf.txt	  Kernel message buffer, including recent console output if
		  the capture facility has been used.  May be disabled by
		  clearing the debug.ddb.textdump.do_msgbuf sysctl.

     panic.txt	  Kernel panic string, if the kernel panicked before the dump
		  was generated.  May be disabled by clearing the
		  debug.ddb.textdump.do_panic sysctl.

     version.txt  Kernel version string.  My be disabled by clearing the
		  debug.ddb.textdump.do_version sysctl.

     Kernel textdumps may be extracted using tar(1).

CONFIGURATION
     The textdump facility is enabled as part of the kernel debugger using
     options KDB and options DDB.  By default, kernel dumps generated on panic
     or via explicit requests for a dump will be regular memory dumps; how‐
     ever, by using the textdump set command in ddb(4), or by setting the
     debug.ddb.textdump.pending sysctl to 1 using sysctl(8), it is possible to
     request that the next dump be a textdump.

     If at the ddb(4) command line, the commands textdump set, textdump
     status, and textdump unset may be used to set, query, and clear the
     textdump pending flag.

     As with regular kernel dumps, a dump partition must be automatically or
     manually configured using dumpon(8).

EXAMPLES
     In the following example, the script kdb.enter.panic will run when the
     kernel debugger is entered as a result of a panic, enable output capture,
     dump several useful pieces of debugging information, and then invoke
     panic in order to force a kernel dump to be written out followed by a
     reboot:

	   script kdb.enter.panic=textdump set; capture on; show allpcpu; bt;
	     ps; alltrace; show alllock; call doadump; reset

     In the following example, the script kdb.enter.witness will run when the
     kernel debugger is entered as a result of a witness violation, printing
     lock-related information for the user:

	   script kdb.enter.witness=show locks

     These scripts may also be configured using the ddb(8) utility.

SEE ALSO
     tar(1), ddb(4), tar(5), ddb(8), dumpon(8), savecore(8), sysctl(8)

HISTORY
     The textdump facility first appeared in FreeBSD 7.1.

AUTHORS
     The textdump facility was created by Robert N. M. Watson.

BSD			       December 24, 2008			   BSD
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