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

NAME

     kdump -- display kernel trace data

SYNOPSIS

     kdump [-dEnlHRSsTA] [-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.  Suppressing 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 or thread pid.  This may be useful when there are multiple processes or
		 threads 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 	 Display system call numbers.

     -s 	 Suppress display of I/O data.

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

     -A 	 Display description of the ABI of traced process.

     -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
     commands:

	   ?> 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
     operation 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 standard 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 operation 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 ker-
     nel, what system call we are returning from, and the return value that the process received.  Seven bytes were written by the writev(2) sys-
     tem 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 wmesg
	   USER    data from user process    the data
	   STRU    various syscalls	     structure
	   SCTL    sysctl(3) requests	     MIB name
	   PFLT    enter page fault	     fault address and type
	   PRET    return from page fault    fault result

SEE ALSO

     ktrace(1)

HISTORY

     The kdump command appeared in 4.4BSD.

BSD
								  March 28, 2014							       BSD