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@(#)ktrace.1 8.1 (Berkeley) 6/6/93
.Dd March 29, 2020 .Dt KTRACE 1 .Os .Sh NAME .Nm ktrace , ktruss .Nd enable kernel process tracing .Sh SYNOPSIS .Nm .Op Fl aCcdins .Op Fl f Ar trfile .Op Fl g Ar pgrp .Op Fl p Ar pid .Op Fl t Ar trstr .Nm .Op Fl adis .Op Fl f Ar trfile .Op Fl t Ar trstr .Ar command .Nm ktruss .Op Fl aCcdilnRT .Op Fl e Ar emulation .Op Fl f Ar infile .Op Fl g Ar pgrp .Op Fl m Ar maxdata .Op Fl o Ar outfile .Op Fl p Ar pid .Op Fl t Ar trstr .Nm ktruss .Op Fl adinRT .Op Fl e Ar emulation .Op Fl m Ar maxdata .Op Fl o Ar outfile .Op Fl t Ar trstr .Op Fl v Ar vers command .Sh DESCRIPTION .Nm enables kernel trace logging for the specified processes. Kernel trace data is logged to the file
a ktrace.out . The kernel operations that are traced include system calls, namei translations, signal processing, and .Tn I/O .
p Once tracing is enabled on a process, trace data will be logged until either the process exits or the tracepoint 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:
p .Dl $ ktrace -C
p The trace file is not human readable; use .Xr kdump 1 to decode it.
p .Nm ktruss is functionally the same as .Nm ktrace except that trace output is printed on standard output or to the file specified with the .Fl o option. .Nm ktruss is useful to see the kernel operations interleaved with the program output.
p The options are as follows: l -tag -width indent t Fl a Append to the trace file instead of truncating it. t Fl C Clear
q disable tracing on all user owned processes, and, if executed by root, all processes in the system. t Fl c Clear
q disable the tracepoints associated with the specified file or processes. t Fl d Descendants; perform the operation for all current children of the designated processes. t Fl e Ar emulation If an emulation of a process is unknown, interpret system call maps assuming the named emulation instead of default "netbsd". t Fl f Ar trfile Log trace records to .Ar trfile instead of
a ktrace.out . t Fl f Ar infile Read the trace records from .Ar infile and print them in a human readable format to standard out. t Fl g Ar pgid Enable
q disable with Fl c tracing on all processes in the process group. Only one .Fl g flag is permitted. t Fl i Inherit; pass the trace flags to all future children of the designated processes. t Fl l Poll the trace file for new data and print it to standard out. Only for use together with the .Fl f option. t Fl m Ar maxdata Print at most .Ar maxdata bytes of data. This is used for pointer type arguments, e.g., strings. The data will be escaped in C-style unless .Fl x is specified when it will be output in hex and ascii. t Fl n Stop tracing if attempts to write to the trace file would block. This option always affects .Nm ktruss and only affects .Nm ktrace when writing to .Dv stdout . If this flag is not set, then the traced program will block until it can write more data to the trace file descriptor. t Fl o Ar outfile Log trace records to .Ar outfile . Without this option .Nm ktruss will print its output in a human readable format to standard out. t Fl p Ar pid Enable
q disable with Fl c tracing on the indicated process id. Only one .Fl p flag is permitted. t Fl R Display relative time stamps to output. t Fl s Write to the trace file with synchronized I/O. t Fl T Same as the .Fl R option, but use absolute timestamps instead. t Fl t Ar trstr The string argument represents the kernel tracepoints, one per letter. The following table equates the letters with the tracepoints:
p
l -tag -width flag -compact t Cm A trace all tracepoints
t Cm a trace exec arguments
t Cm c trace system calls
t Cm e trace emulation changes
t Cm f trace open file descriptors after exec
t Cm i trace
.Tn I/O
t Cm n trace namei translations
t Cm S trace MIB access (sysctl)
t Cm s trace signal processing
.It Cm U
trace scheduler activations upcall data
t Cm u trace user data
t Cm v trace exec environment
t Cm w trace context switches
t Cm + trace the default set of tracepoints (c, e, i, n, s, u)
t Cm - do not trace following tracepoints
.El
t Fl v Ar version Determines the
.Ar 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.
t Ar command Execute
.Ar command
with the specified trace flags.
.El
p The .Fl p , .Fl g , and .Ar command options are mutually exclusive. The .Fl R and .Fl T options are also mutually exclusive. .Sh EXAMPLES # trace all kernel operations of process id 34 .Dl $ ktrace -p 34
p d -literal # trace all kernel operations of processes in process group 15 and # pass the trace flags to all current and future children .Ed .Dl $ ktrace -idg 15
p # disable all tracing of process 65 .Dl $ ktrace -cp 65
p # disable tracing signals on process 70 and all current children .Dl $ ktrace -t s -cdp 70
p # enable tracing of .Tn I/O on process 67 .Dl $ ktrace -ti -p 67
p # run the command "w", tracing only system calls .Dl $ ktrace -tc w
p # disable all tracing to the file "tracedata" .Dl $ ktrace -c -f tracedata
p # disable tracing of all processes owned by the user .Dl $ ktrace -C
p # run the command "w", displaying to standard output .Dl $ ktruss w
p # trace process 42 and log the records to "ktruss.out" .Dl $ ktruss -p 42 -o ktruss.out
p # poll ktruss.out for available records and print them .Dl $ ktruss -lf ktruss.out .Sh SEE ALSO .Xr kdump 1 , .Xr ktrace 2 .Sh HISTORY The .Nm command appeared in x 4.4 . The .Nm ktruss command appeared in .Nx 1.5 .
Indexes created Sun Sep 21 19:09:51 GMT 2025