enable kernel process tracing
ktrace utility enables kernel trace logging for the
specified processes. Kernel trace data is logged to the file
ktrace.out. The kernel operations that are traced
include system calls, namei translations, signal processing, and I/O.
Once tracing is enabled on a process, trace data will be logged
until either the process exits or the trace point is cleared. A traced
process can generate enormous amounts of log data quickly; It is strongly
suggested 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
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:
- Append to the trace file instead of recreating it.
- Disable tracing on all user-owned processes, and, if executed by root, all
processes in the system.
- Clear the specified trace points associated with the given file or
- Descendants; perform the operation for all current children of the
designated processes. See also the
- Log trace records to trfile instead of
- Enable (disable) tracing on all processes in the process group (only one
-g flag is permitted).
- Inherit; pass the trace flags to all future children of the designated
processes. See also the
- Enable (disable) tracing on the indicated process id (only one
-p flag is permitted).
- 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
The following trace points are supported:
- trace system calls
- trace page faults
- trace I/O
- trace namei translations
- trace capability check failures
- trace signal processing
- trace various structures
- userland traces generated by
- context switches
- trace the default set of trace points -
- Execute command with the specified trace flags.
Run "make", then trace it and any child processes:
command options are mutually exclusive.
$ ktrace -i make
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
$ ktrace -t s -cdp 70
Enable tracing of I/O on process 67:
$ ktrace -ti -p 67
Disable all tracing to the file "tracedata":
$ ktrace -c -f tracedata
Disable tracing of all user-owned processes:
$ ktrace -C
ktrace command appeared in
Only works if trfile is a regular file.