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KTRACE(1)		  BSD General Commands Manual		     KTRACE(1)

     ktrace -- enable kernel process tracing

     ktrace [-aCcdi] [-f trfile] [-g pgrp | -p pid] [-t	trstr]
     ktrace [-adi] [-f trfile] [-t trstr] command

     The ktrace	utility	enables	kernel trace logging for the specified pro-
     cesses.  Kernel trace data	is logged to the file ktrace.out.  The kernel
     operations	that are traced	include	system calls, namei translations, sig-
     nal processing, and I/O.

     Once tracing is enabled on	a process, trace data will be logged until ei-
     ther the process exits or the trace point is cleared.  A traced process
     can generate enormous amounts of log data quickly;	It is strongly sug-
     gested that users memorize	how to disable tracing before attempting to
     trace a process.  The following command is	sufficient to disable tracing
     on	all user-owned processes, and, if executed by root, all	processes:

	   $ ktrace -C

     The trace file is not human readable; use kdump(1)	to decode it.

     The utility may be	used only with a kernel	that has been built with the
     "KTRACE" option in	the kernel configuration file.

     The options are:

     -a	     Append to the trace file instead of recreating it.

     -C	     Disable tracing on	all user-owned processes, and, if executed by
	     root, all processes in the	system.

     -c	     Clear the specified trace points associated with the given	file
	     or	processes.

     -d	     Descendants; perform the operation	for all	current	children of
	     the designated processes.

     -f	trfile
	     Log trace records to trfile instead of ktrace.out.

     -g	pgid
	     Enable (disable) tracing on all processes in the process group
	     (only one -g flag is permitted).

     -i	     Inherit; pass the trace flags to all future children of the des-
	     ignated processes.

     -p	pid  Enable (disable) tracing on the indicated process id (only	one -p
	     flag is permitted).

     -t	trstr
	     Specify the list of trace points to enable	or disable, one	per
	     letter.  If an explicit list is not specified, the	default	set of
	     trace points is used.

	     The following trace points	are supported:

	     c	   trace system	calls
	     f	   trace page faults
	     i	   trace I/O
	     n	   trace namei translations
	     p	   trace capability check failures
	     s	   trace signal	processing
	     t	   trace various structures
	     u	   userland traces
	     w	   context switches
	     y	   trace sysctl(3) requests
	     +	   trace the default set of trace points - c, i, n, p, s, t,
		   u, y

	     Execute command with the specified	trace flags.

     The -p, -g, and command options are mutually exclusive.

     # trace all kernel	operations of process id 34
	   $ ktrace -p 34

     # trace all kernel	operations of processes	in process group 15 and	# pass
     the trace flags to	all current and	future children
	   $ ktrace -idg 15

     # disable all tracing of process 65
	   $ ktrace -cp	65

     # disable tracing signals on process 70 and all current children
	   $ ktrace -t s -cdp 70

     # enable tracing of I/O on	process	67
	   $ ktrace -ti	-p 67

     # run the command "w", tracing only system	calls
	   $ ktrace -tc	w

     # disable all tracing to the file "tracedata"
	   $ ktrace -c -f tracedata

     # disable tracing of all user-owned processes
	   $ ktrace -C

     kdump(1), ktrace(2)

     The ktrace	command	appeared in 4.4BSD.

     Only works	if trfile is a regular file.

BSD				March 31, 2016				   BSD


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