NAME¶
ktrace —
enable kernel process
tracing
SYNOPSIS¶
ktrace |
[-aCcdi]
[-f
trfile]
[-g pgrp |
-p pid]
[-t
trstr] |
ktrace |
[-adi]
[-f
trfile]
[-t trstr]
command |
DESCRIPTION¶
The
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
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 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
designated 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 tracepoints:
- 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
- trace sysctl(3) requests
- +
- trace the default set of trace points -
c, i, n,
s, t, u,
y
- command
- Execute command with the specified
trace flags.
The
-p,
-g, and
command options are mutually exclusive.
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 user-owned processes
$ ktrace -C
SEE ALSO¶
kdump(1)
HISTORY¶
The
ktrace command appeared in
4.4BSD.
BUGS¶
Only works if
trfile is a regular file.