ktrace(1) - NetBSD Manual Pages

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KTRACE(1)               NetBSD General Commands Manual               KTRACE(1)


NAME

     ktrace, ktruss -- enable kernel process tracing


SYNOPSIS

     ktrace [-aCcdins] [-f trfile] [-g pgrp] [-p pid] [-t trstr]
     ktrace [-adis] [-f trfile] [-t trstr] command
     ktruss [-aCcdilnRT] [-e emulation] [-f infile] [-g pgrp] [-m maxdata]
            [-o outfile] [-p pid] [-t trstr]
     ktruss [-adinRT] [-e emulation] [-m maxdata] [-o outfile] [-t trstr]
            [-v vers] command


DESCRIPTION

     ktrace enables kernel trace logging for the specified processes.  Kernel
     trace data is logged to the file ktrace.out.  The kernel operations that
     are traced include system calls, namei translations, signal processing,
     and I/O.

     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 sug-
     gested 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:

           $ ktrace -C

     The trace file is not human readable; use kdump(1) to decode it.

     ktruss is functionally the same as ktrace except that trace output is
     printed on standard output or to the file specified with the -o option.
     ktruss is useful to see the kernel operations interleaved with the pro-
     gram output.

     The options are as follows:

     -a      Append to the trace file instead of truncating it.

     -C      Disable tracing on all user owned processes, and, if executed by
             root, all processes in the system.

     -c      Clear the trace points associated with the specified file or pro-
             cesses.

     -d      Descendants; perform the operation for all current children of
             the designated processes.

     -e emulation
             If an emulation of a process is unknown, interpret system call
             maps assuming the named emulation instead of default "netbsd".

     -f trfile
             Log trace records to trfile instead of ktrace.out.

     -f infile
             Read the trace records from infile and print them in a human
             readable format to standard out.

     -g pgid
             Enable (disable) tracing on all processes in the process group
             (only one -g flag is permitted).

     -i      Inherit; pass the trace flags to all future children of the des-
             ignated processes.

     -l      Poll the trace file for new data and print it to standard out.
             Only for use together with the -f option.

     -m maxdata
             Print at most maxdata bytes of data.  This is used for pointer
             type arguments, e.g., strings.  The data will be escaped in C-
             style unless -x is specified when it will be output in hex and
             ascii.

     -n      Stop tracing if attempts to write to the trace file would block.
             This option always affects ktruss and only affects ktrace when
             writing to stdout.  If this flag is not set, then the traced pro-
             gram will block until it can write more data to the trace file
             descriptor.

     -o outfile
             Log trace records to outfile.  Without this option ktruss will
             print its output in a human readable format to standard out.

     -p pid  Enable (disable) tracing on the indicated process id (only one -p
             flag is permitted).

     -R      Display relative time stamps to output.

     -s      Write to the trace file with synchronized I/O.

     -T      Same as the -R option, but use absolute timestamps instead.

     -t trstr
             The string argument represents the kernel trace points, one per
             letter.  The following table equates the letters with the trace-
             points:

             A     trace all tracepoints
             a     trace exec arguments
             c     trace system calls
             e     trace emulation changes
             f     trace open file descriptors after exec
             i     trace I/O
             n     trace namei translations
             S     trace MIB access (sysctl)
             s     trace signal processing
             u     trace user data
             v     trace exec environment
             w     trace context switches
             +     trace the default set of trace points (c, e, i, n, s, u)
             -     do not trace following trace points

     -v version
             Determines the 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.

     command
             Execute command with the specified trace flags.

     The -p, -g, and command options are mutually exclusive.  The -R and -T
     options are also mutually exclusive.


EXAMPLES

     # trace all kernel operations of process id 34
           $ ktrace -p 34

     # trace all kernel operations of processes in process group 15 and
     # pass the trace flags to all current and future children
           $ ktrace -idg 15

     # disable all tracing of process 65
           $ ktrace -cp 65

     # disable tracing signals on process 70 and all current children
           $ ktrace -t s -cdp 70

     # enable tracing of I/O on process 67
           $ ktrace -ti -p 67

     # run the command "w", tracing only system calls
           $ ktrace -tc w

     # disable all tracing to the file "tracedata"
           $ ktrace -c -f tracedata

     # disable tracing of all processes owned by the user
           $ ktrace -C

     # run the command "w", displaying to standard output
           $ ktruss w

     # trace process 42 and log the records to "ktruss.out"
           $ ktruss -p 42 -o ktruss.out

     # poll ktruss.out for available records and print them
           $ ktruss -lf ktruss.out


SEE ALSO

     kdump(1), ktrace(2)


HISTORY

     The ktrace command appeared in 4.4BSD.  The ktruss command appeared in
     NetBSD 1.5.

NetBSD 10.1                     March 29, 2020                     NetBSD 10.1