---
name: "ddb"
section: "8"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/ddb"
---

# ddb(8)

configure DDB kernel debugger properties

## NAME

**ddb** – configure DDB kernel debugger properties

## SYNOPSIS

**ddb** **capture** \[**-M** **-core**\] \[**-N** **-system**\] **print**

**ddb** **capture** \[**-M** **-core**\] \[**-N** **-system**\] **status**

**ddb** **script** *scriptname*

**ddb** **script** *scriptname*=*script*

**ddb** **scripts**

**ddb** **unscript** *scriptname*

**ddb** *pathname*

## DESCRIPTION

The **ddb** utility configures certain aspects of the [ddb(4)](/ddb/4.md) kernel debugger from user space that are not configured at compile-time or easily via [sysctl(8)](/sysctl/8.md) MIB entries.

To ease configuration, commands can be put in a file which is processed using **ddb** as shown in the last synopsis line. An absolute *pathname* must be used. The file will be read line by line and applied as arguments to the **ddb** utility. Whitespace at the beginning of lines will be ignored as will lines where the first non-whitespace character is ‘#’.

## OUTPUT CAPTURE

The **ddb** utility can be used to extract the contents of the [ddb(4)](/ddb/4.md) output capture buffer of the current live kernel, or from the crash dump of a kernel on disk. The following debugger commands are available from the command line:

-

  **capture** \[**-M** *core*\] \[**-N** *system*\] **print** Print the current contents of the [ddb(4)](/ddb/4.md) output capture buffer.

-

  **capture** \[**-M** *core*\] \[**-N** *system*\] **status** Print the current status of the [ddb(4)](/ddb/4.md) output capture buffer.

## SCRIPTING

The **ddb** utility can be used to configure aspects of [ddb(4)](/ddb/4.md) scripting from user space; scripting support is described in more detail in [ddb(4)](/ddb/4.md). Each of the debugger commands is available from the command line:

- **script** *scriptname*

  Print the script named *scriptname*.

- **script** *scriptname*=*script*

  Define a script named *scriptname*. As many scripts contain characters interpreted in special ways by the shell, it is advisable to enclose *script* in quotes.

- **scripts**

  List currently defined scripts.

- **unscript** *scriptname*

  Delete the script named *scriptname*.

## EXIT STATUS

The **ddb** utility exits 0 on success, and \>0 if an error occurs.

## EXAMPLES

The following example defines a script that will execute when the kernel debugger is entered as a result of a break signal:

```
ddb script kdb.enter.break="show pcpu; bt"
```

The following example will delete the script:

```
ddb unscript kdb.enter.break
```

For further examples, see the [ddb(4)](/ddb/4.md) and [textdump(4)](/textdump/4.md) manual pages.

## SEE ALSO

[ddb(4)](/ddb/4.md), [mac\_ddb(4)](/mac_ddb/4.md), [textdump(4)](/textdump/4.md), [sysctl(8)](/sysctl/8.md)

## HISTORY

The **ddb** utility first appeared in FreeBSD 7.1.

## AUTHORS

Robert N M Watson

## BUGS

Ideally, **ddb** would not exist, as all pertinent aspects of [ddb(4)](/ddb/4.md) could be configured directly via [sysctl(8)](/sysctl/8.md).