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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 .

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