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

NAME

     textdump -- textdump 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
     normally 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 information can be captured in a fully automated manner.

FORMAT

     textdump data is stored in a dump partition in the same style as a regular 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; however, 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 cap-
     ture, 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