kdump(1)

kdump1

Display kernel trace data

Usage

kdump [-dHlnRTXx] [-f file] [-m maxdata] [-P program] [-p pid] [-t trstr] [-u label]

Overview

kdump displays the kernel trace files produced with ktrace(1) in human-readable format. By default, the file ktrace.out in the current directory is displayed, unless overridden by the -f option.

The options are as follows:

-d

Display all numbers in decimal. By default, values are printed out in hexadecimal.

-f file

Display the specified file instead of ktrace.out. Specifying ‘-’ will read from standard input.

-H

Display thread identifiers.

-l

Loop reading the trace file, once the end-of-file is reached, waiting for more data.

-m maxdata

Display at most maxdata bytes when decoding I/O.

-n

Suppress ad hoc translations. Normally kdump tries to decode many system calls into a more human-readable format. For example, ioctl(2) values are replaced with the macro name and errno values are replaced with the strerror(3) string. Suppressing this feature yields a more consistent output format and is easily amenable to further processing.

-P program

Show output only for processes with program as their command name.

-p pid

Show output only for the pid specified.

-R

Display relative timestamps (time since previous entry).

-T

Display absolute timestamps for each entry (seconds since the Epoch).

-TR

If both options are specified, display timestamps relative to trace start.

-t trstr

Select which tracepoints to display. The argument can contain one or more of the following letters. By default all trace points except for X are enabled.

c

trace system calls

i

trace I/O

n

trace namei translations

p

trace violation of pledge(2) restrictions

s

trace signal processing

S

trace violation of pinsyscalls(2)

t

trace various structures

u

trace user data coming from utrace(2)

x

trace argument vector in execve(2)

X

trace environment in execve(2)

+

trace the default points

-u label

Display utrace(2) tracepoints having utrace(2) label label as strings with vis(3) escaping, without ktrace(2) header information.

-X

Display I/O data with hexadecimal data and printable ASCII characters side by side.

-x

Display I/O data in hexadecimal.

The -t and -u options are mutually exclusive; the last one specified overrides any previous ones.

Files

ktrace.out

default ktrace dump file

Releases

61 releases since OpenBSD 2.1; the text changed 20 times.

  1. 2.1–2.3
  2. 2.4–2.5
  3. 2.6
  4. 2.7–3.1
  5. 3.2
  6. 3.3
  7. 3.4–3.9
  8. 4.0
  9. 4.1
  10. 4.2–4.9
  11. 5.0–5.1
  12. 5.2–5.3
  13. 5.4–5.6
  14. 5.7–5.8
  15. 5.9
  16. 6.0–6.4
  17. 6.5
  18. 6.6–7.1
  19. 7.2–7.3
  20. 7.4
  21. 7.5–8.0

-H since OpenBSD 5.2; -P since OpenBSD 7.5; -TR since OpenBSD 6.0; -X since OpenBSD 4.0; -p since OpenBSD 3.2; -u since OpenBSD 7.4; -x since OpenBSD 4.0.

-e until OpenBSD 5.9; -r until OpenBSD 5.6.

History

The kdump command appeared in 4.3BSD-Reno.

From man 8.0-current-20261101 in OpenBSD 8.0-current (2026-11-01). Parsed by carta from the page's mdoc source.