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KDUMP(1)		FreeBSD	General	Commands Manual		      KDUMP(1)

NAME
     kdump -- display kernel trace data

SYNOPSIS
     kdump [-dEnlHRsT] [-f trfile] [-m maxdata]	[-p pid] [-t [cnisuw]]

DESCRIPTION
     The kdump command displays	the kernel trace files produced	with ktrace(1)
     in	human readable format.	By default, the	file ktrace.out	in the current
     directory is displayed.

     The options are as	follows:

     -d		 Display all numbers in	decimal.

     -E		 Display elapsed timestamps (time since	beginning of trace).

     -f	trfile	 Display the specified file instead of ktrace.out.

     -H		 List the thread ID (tid) of the thread	with each trace
		 record, if available.	If no thread ID	is available, 0	will
		 be printed.

     -l		 Loop reading the trace	file, once the end-of-file is reached,
		 waiting for more data.

     -m	maxdata	 Display at most maxdata bytes when decoding I/O.

     -n		 Suppress ad hoc translations.	Normally kdump tries to	decode
		 many system calls into	a more human readable format.  For
		 example, ioctl(2) values are replaced with the	macro name and
		 errno values are replaced with	the strerror(3)	string.	 Sup-
		 pressing this feature yields a	more consistent	output format
		 and is	easily amenable	to further processing.

     -p	pid	 Display only trace events that	correspond to the process pid.
		 This may be useful when there are multiple processes recorded
		 in the	same trace file.

     -R		 Display relative timestamps (time since previous entry).

     -s		 Suppress display of I/O data.

     -T		 Display absolute timestamps for each entry (seconds since
		 epoch).

     -t	cnisuw	 See the -t option of ktrace(1).

     The output	format of kdump	is line	oriented with several fields.  The
     example below shows a section of a	kdump generated	by the following com-
     mands:

	   ?> ktrace echo "ktrace"

	   ?> kdump

	    85045 echo	   CALL	 writev(0x1,0x804b030,0x2)
	    85045 echo	   GIO	 fd 1 wrote 7 bytes
		  "ktrace
		  "
	    85045 echo	   RET	 writev	7

     The first field is	the PID	of the process being traced.  The second field
     is	the name of the	program	being traced.  The third field is the opera-
     tion that the kernel performed on behalf of the process.  If thread IDs
     are being printed,	then an	additional thread ID column will be added to
     the output	between	the PID	field and program name field.

     In	the first line above, the kernel executes the writev(2)	system call on
     behalf of the process so this is a	CALL operation.	 The fourth field
     shows the system call that	was executed, including	its arguments.	The
     writev(2) system call takes a file	descriptor, in this case 1, or stan-
     dard output, then a pointer to the	iovector to write, and the number of
     iovectors that are	to be written.	In the second line we see the opera-
     tion was GIO, for general I/O, and	that file descriptor 1 had seven bytes
     written to	it.  This is followed by the seven bytes that were written,
     the string	"ktrace" with a	carriage return	and line feed.	The last line
     is	the RET	operation, showing a return from the kernel, what system call
     we	are returning from, and	the return value that the process received.
     Seven bytes were written by the writev(2) system call, so 7 is the	return
     value.

     The possible operations are:

	   Name	    Operation		      Fourth field
	   CALL	    enter syscall	      syscall name and arguments
	   RET	    return from	syscall	      syscall name and return value
	   NAMI	    file name lookup	      path to file
	   GENIO    general I/O		      fd, read/write, number of	bytes
	   SIG	    signal		      signal name, handler, mask, code
	   CSW	    context switch	      stop/resume user/kernel
	   USER	    data from user process    the data

SEE ALSO
     ktrace(1)

HISTORY
     The kdump command appeared	in 4.4BSD.

FreeBSD	9.2		       November	12, 2005		   FreeBSD 9.2

NAME | SYNOPSIS | DESCRIPTION | SEE ALSO | HISTORY

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