---
name: "kdump"
section: "1"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["freebsd", "openbsd"]
url: "https://new.carta.tech/kdump"
---

# kdump(1)

display kernel trace data

## NAME

**kdump** – display kernel trace data

## SYNOPSIS

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

## DESCRIPTION

**kdump** displays the kernel trace files produced with [ktrace(1)](/ktrace/1.md) 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)](/ioctl/2.md) values are replaced with the macro name and *errno* values are replaced with the [strerror(3)](/strerror/3.md) 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)](/utrace/2.md)

  - **x**

    trace argument vector in [execve(2)](/execve/2.md)

  - **X**

    trace environment in [execve(2)](/execve/2.md)

  - **+**

    trace the default points

- **-u** *label*

  Display [utrace(2)](/utrace/2.md) tracepoints having [utrace(2)](/utrace/2.md) label *label* as strings with [vis(3)](/vis/3.md) escaping, without [ktrace(2)](/ktrace/2.md) 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

## SEE ALSO

[ktrace(1)](/ktrace/1.md)

## HISTORY

The **kdump** command appeared in 4.3BSD-Reno.