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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
.Pa ktrace.out .
The kernel operations that are traced include system calls, namei
translations, signal processing, and
.Tn I/O .
.Pp
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:
.Pp
.Dl \&$ ktrace -C
.Pp
The trace file is not human readable; use
.Xr kdump 1
to decode it.
.Pp
.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.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl a
Append to the trace file instead of truncating it.
.It Fl C
Clear
.Pq disable
tracing on all user owned processes, and, if executed by root, all
processes in the system.
.It Fl c
Clear
.Pq disable
the tracepoints associated with the specified file or processes.
.It Fl d
Descendants; perform the operation for all current children of the
designated processes.
.It Fl e Ar emulation
If an emulation of a process is unknown,
interpret system call maps assuming the named emulation instead of
default "netbsd".
.It Fl f Ar trfile
Log trace records to
.Ar trfile
instead of
.Pa ktrace.out .
.It Fl f Ar infile
Read the trace records from
.Ar infile
and print them in a human readable format to standard out.
.It Fl g Ar pgid
Enable
.Pq disable with Fl c
tracing on all processes in the process group.
Only one
.Fl g
flag is permitted.
.It Fl i
Inherit; pass the trace flags to all future children of the designated
processes.
.It Fl l
Poll the trace file for new data and print it to standard out.
Only for use together with the
.Fl f
option.
.It 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.
.It 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.
.It 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.
.It Fl p Ar pid
Enable
.Pq disable with Fl c
tracing on the indicated process id.
Only one
.Fl p
flag is permitted.
.It Fl R
Display relative time stamps to output.
.It Fl s
Write to the trace file with synchronized I/O.
.It Fl T
Same as the
.Fl R
option, but use absolute timestamps instead.
.It Fl t Ar trstr
The string argument represents the kernel tracepoints, one per letter.
The following table equates the letters with the tracepoints:
.Pp
.Bl -tag -width flag -compact
.It Cm A
trace all tracepoints
.It Cm a
trace exec arguments
.It Cm c
trace system calls
.It Cm e
trace emulation changes
.It Cm f
trace open file descriptors after exec
.It Cm i
trace
.Tn I/O
.It Cm n
trace namei translations
.It Cm S
trace MIB access (sysctl)
.It Cm s
trace signal processing
.\" .It Cm U
.\" trace scheduler activations upcall data
.It Cm u
trace user data
.It Cm v
trace exec environment
.It Cm w
trace context switches
.It Cm +
trace the default set of tracepoints (c, e, i, n, s, u)
.It Cm -
do not trace following tracepoints
.El
.It 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.
.It Ar command
Execute
.Ar command
with the specified trace flags.
.El
.Pp
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
.Pp
.Bd -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
.Pp
# disable all tracing of process 65
.Dl $ ktrace -cp 65
.Pp
# disable tracing signals on process 70 and all current children
.Dl $ ktrace -t s -cdp 70
.Pp
# enable tracing of
.Tn I/O
on process 67
.Dl $ ktrace -ti -p 67
.Pp
# run the command "w", tracing only system calls
.Dl $ ktrace -tc w
.Pp
# disable all tracing to the file "tracedata"
.Dl $ ktrace -c -f tracedata
.Pp
# disable tracing of all processes owned by the user
.Dl $ ktrace -C
.Pp
# run the command "w", displaying to standard output
.Dl $ ktruss w
.Pp
# trace process 42 and log the records to "ktruss.out"
.Dl $ ktruss -p 42 -o ktruss.out
.Pp
# 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
.Bx 4.4 .
The
.Nm ktruss
command appeared in
.Nx 1.5 .