KTRACE(1) BSD General Commands Manual KTRACE(1)NAME
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
either 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 trace points associated with the specified file or pro‐
-d Descendants; perform the operation for all current children of
the designated processes.
Log trace records to trfile instead of ktrace.out.
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‐
-p pid Enable (disable) tracing on the indicated process id (only one -p
flag is permitted).
The string argument represents the kernel trace points, one per
letter. The following table equates the letters with the trace‐
c trace system calls
i trace I/O
n trace namei translations
s trace signal processing
t trace various structures
u userland traces
w context switches
y tracesysctl(3) requests
+ trace the default set of trace points - c, i, n, 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
The ktrace command appeared in 4.4BSD.
Only works if trfile is a regular file.
BSD February 23, 2008 BSD