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KTRACE(1) NetBSD General Commands Manual KTRACE(1)
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ktrace, ktruss -- enable kernel process tracing
ktrace [-aCcdins] [-f trfile] [-g pgrp] [-p pid] [-t trstr]
ktrace [-adis] [-f trfile] [-t trstr] command
ktruss [-aCcdilnRT] [-e emulation] [-f infile] [-g pgrp] [-m maxdata]
[-o outfile] [-p pid] [-t trstr]
ktruss [-adinRT] [-e emulation] [-m maxdata] [-o outfile] [-t trstr]
[-v vers] command
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,
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.
ktruss is functionally the same as ktrace except that trace output is
printed on standard output or to the file specified with the -o option.
ktruss is useful to see the kernel operations interleaved with the pro-
The options are as follows:
-a Append to the trace file instead of truncating it.
-C Clear (disable) tracing on all user owned processes, and, if exe-
cuted by root, all processes in the system.
-c Clear (disable) the trace points associated with the specified
file or processes.
-d Descendants; perform the operation for all current children of
the designated processes.
If an emulation of a process is unknown, interpret system call
maps assuming the named emulation instead of default "netbsd".
Log trace records to trfile instead of ktrace.out.
Read the trace records from infile and print them in a human
readable format to standard out.
Enable (disable with -c) 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-
-l Poll the trace file for new data and print it to standard out.
Only for use together with the -f option.
Print at most maxdata bytes of data. This is used for pointer
type arguments, e.g., strings. The data will be escaped in C-
style unless -x is specified when it will be output in hex and
-n Stop tracing if attempts to write to the trace file would block.
This option always affects ktruss and only affects ktrace when
writing to stdout. If this flag is not set, then the traced pro-
gram will block until it can write more data to the trace file
Log trace records to outfile. Without this option ktruss will
print its output in a human readable format to standard out.
-p pid Enable (disable with -c) tracing on the indicated process id.
Only one -p flag is permitted.
-R Display relative time stamps to output.
-s Write to the trace file with synchronized I/O.
-T Same as the -R option, but use absolute timestamps instead.
The string argument represents the kernel trace points, one per
letter. The following table equates the letters with the trace-
A trace all tracepoints
a trace exec arguments
c trace system calls
e trace emulation changes
f trace open file descriptors after exec
i trace I/O
n trace namei translations
S trace MIB access (sysctl)
s trace signal processing
u trace user data
v trace exec environment
w trace context switches
+ trace the default set of trace points (c, e, i, n, s, u)
- do not trace following trace points
Determines the version of the file generated. Version 0 is the
compatible ktrace format, and version 1 is the new format with
lwp IDs and nanosecond (instead of microsecond) timestamps.
Execute command with the specified trace flags.
The -p, -g, and command options are mutually exclusive. The -R and -T
options are also 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 processes owned by the user
$ ktrace -C
# run the command "w", displaying to standard output
$ ktruss w
# trace process 42 and log the records to "ktruss.out"
$ ktruss -p 42 -o ktruss.out
# poll ktruss.out for available records and print them
$ ktruss -lf ktruss.out
The ktrace command appeared in 4.4BSD. The ktruss command appeared in
NetBSD 10.99 March 29, 2020 NetBSD 10.99