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.\"	from: @(#)ktrace.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: June 1 2013 $
.Dt KTRACE 1
.Os
.Sh NAME
.Nm ktrace
.Nd enable kernel process tracing
.Sh SYNOPSIS
.Nm ktrace
.Op Fl aBCcdi
.Op Fl f Ar trfile
.Op Fl g Ar pgid
.Op Fl p Ar pid
.Op Fl t Ar trstr
.Nm ktrace
.Op Fl adi
.Op Fl f Ar trfile
.Op Fl t Ar trstr
.Ar command
.Sh DESCRIPTION
.Nm ktrace
enables kernel trace logging for the specified processes.
By default, kernel trace data is logged to the file
.Pa ktrace.out ,
unless overridden by the
.Fl f
option.
The kernel operations traced are system calls, namei translations,
signal processing, I/O and emulation changes.
.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 9n
.It Fl a
Append to the trace file instead of recreating it.
.It Fl B
Set the
.Ev LD_BIND_NOW
environment variable to specify that the dynamic linker should process
relocations immediately instead of as they are encountered.
This eliminates the resulting
.Xr ld.so 1
relocation sequences.
.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 trace file or any specified
processes.
.It Fl d
Descendants; perform the operation for all current children of the
designated processes.
.It Fl f Ar trfile
Log trace records to
.Ar trfile
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 default flags are
.Cm c ,
.Cm e ,
.Cm i ,
.Cm n ,
.Cm s ,
.Cm t ,
and
.Cm u .
The following table equates the letters with the tracepoints:
.Pp
.Bl -tag -width flag -offset indent -compact
.It Cm c
trace system calls
.It Cm e
trace emulation changes
.It Cm i
trace I/O
.It Cm n
trace namei translations
.It Cm s
trace signal processing
.It Cm t
trace various structures
.It Cm u
trace user data coming from
.Xr utrace 2
.It Cm w
trace context switch points
.It Cm +
trace the default points
.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 FILES
.Bl -tag -width ktrace.out -compact
.It Pa ktrace.out
default ktrace dump file
.El
.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 I/O on process 67:
.Dl $ ktrace -ti -p 67
.Pp
Run the command
.Xr w 1 ,
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 ,
.Xr ktrace 2 ,
.Xr utrace 2
.Sh HISTORY
The
.Nm ktrace
command appeared in
.Bx 4.4 .