.\" Copyright (c) 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\"    must display the following acknowledgement:
.\"	This product includes software developed by the University of
.\"	California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
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.\"	@(#)ktrace.1	8.1 (Berkeley) 6/6/93
.\" $FreeBSD: src/usr.bin/ktrace/ktrace.1,v 1.8.2.5 2001/08/16 13:16:53 ru Exp $
.\"
.Dd June 6, 1993
.Dt KTRACE 1
.Os
.Sh NAME
.Nm ktrace
.Nd enable kernel process tracing
.Sh SYNOPSIS
.Nm
.Op Fl aCcdi
.Op Fl f Ar trfile
.Op Fl g Ar pgrp | Fl p Ar pid
.Op Fl t Ar trstr
.Nm
.Op Fl adi
.Op Fl f Ar trfile
.Op Fl t Ar trstr
.Ar command
.Sh DESCRIPTION
The
.Nm
command 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 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:
.Pp
.Dl \&$ ktrace -C
.Pp
The trace file is not human readable; use
.Xr kdump 1
to decode it.
.Pp
The options are as follows:
.Bl -tag -width indent
.It Fl a
Append to the trace file instead of recreating it.
.It Fl C
Disable tracing on all user owned processes, and, if executed by root, all
processes in the system.
.It Fl c
Clear the trace points associated with the specified file or processes.
.It Fl d
Descendants; perform the operation for all current children of the
designated processes.
.It Fl f Ar file
Log trace records to
.Ar file
instead of
.Pa ktrace.out .
.It Fl g Ar pgid
Enable (disable) 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 p Ar pid
Enable (disable) tracing on the indicated process id (only one
.Fl p
flag is permitted).
.It Fl t Ar trstr
The string argument represents the kernel trace points, one per letter.
The following table equates the letters with the tracepoints:
.Pp
.Bl -tag -width flag -compact
.It Cm c
trace system calls
.It Cm n
trace namei translations
.It Cm i
trace
.Tn I/O
.It Cm s
trace signal processing
.It Cm u
userland traces
.It Cm w
context switches
.El
.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.
.Sh EXAMPLES
# trace all kernel operations of process id 34
.Dl $ ktrace -p 34
.Pp
# trace all kernel operations of processes in process group 15 and
# pass the trace flags to all current and future children
.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
.Sh SEE ALSO
.Xr kdump 1
.Sh BUGS
Only works if
.Ar file
is a regular file.
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.4 .