kdump man page on FreeBSD

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KDUMP(1)		  BSD General Commands Manual		      KDUMP(1)

NAME
     kdump — display kernel trace data

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

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).

     -r		 When decoding STRU records, display structure members such as
		 UIDs, GIDs, dates etc. symbolically instead of numerically.

     -s		 Suppress display of I/O data.

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

     -t trstr	 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
	   GIO	   general I/O		     fd, read/write, number of bytes
	   PSIG	   signal		     signal name, handler, mask, code
	   CSW	   context switch	     stop/resume user/kernel
	   USER	   data from user process    the data
	   STRU	   various syscalls	     structure
	   SCTL	   sysctl(3) requests	     MIB name

SEE ALSO
     ktrace(1)

HISTORY
     The kdump command appeared in 4.4BSD.

BSD			       February 23, 2008			   BSD
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