KTRACE(1) BSD Reference Manual KTRACE(1)NAMEktrace - enable kernel process tracing
SYNOPSISktrace [-aCcdi] [-f trfile] [-g pgrp] [-p pid] [-t trstr]
ktrace [-adi] [-f trfile] [-t trstr] command
DESCRIPTION
Ktrace 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,
I/O, and context switches. The default is system calls, namei transla-
tions, signal processing and I/O, which may be changed with the -t op-
tion.
Once tracing is enabled on a process, trace data will be logged until ei-
ther the process exits or the trace point is cleared. The ktrace program
does not take part in collecting trace data; it merely instructs the giv-
en process to generate trace data, and exits or executes a command.
A traced process can generate enormous amounts of log data quickly. It
is suggested that users review how to disable tracing before attempting
to trace a process. The following command is sufficient to disable trac-
ing 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 options are as follows:
-a Append to the trace file instead of truncating 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-
cesses.
-d Descendants; perform the operation for all current children of
the designated processes.
-f file
Log trace records to file instead of the default ktrace.out. The
file argument must be a regular file and writable by the process.
-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
The string argument represents the kernel trace points, one per
letter. The following table equates the letters with the trace-
points:
+ trace default points (equivalent to cins)
a trace all points
c trace system calls
i trace I/O
n trace namei translations
s trace signal processing
w trace context switches
command
Execute command with the specified trace flags.
The -p, -g, and command options are mutually exclusive.
The ktrace utility exits 0 on success and nonzero if an error occurs. To
trace a process, you must either be the superuser or your real UID must
match the real UID of the process. If you don't have superuser privi-
leges, you can't trace a set-UID or set-GID process or change the tracing
status of a process that a superuser process is already tracing. If you
don't have sufficient privileges to trace any of the processes that you
requested, ktrace prints an error message and exits with nonzero status;
otherwise, ktrace enables tracing on the processes that you do have per-
mission to trace and ignores any others.
EXAMPLES
# 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 processes owned by the user
$ ktrace-C
SEE ALSOkdump(1), ktrace(2)HISTORY
The ktrace command appears in 4.4BSD.
4.4BSD May 7, 1998 2