---
name: "boot.config"
section: "5"
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/boot.config"
---

# boot.config(5)

Configuration file for the legacy boot blocks

## NAME

**boot.config** – Configuration file for the legacy boot blocks

## DESCRIPTION

The **boot.config** file contains options for the FreeBSD boot block code.

When the first- and second-stage FreeBSD boot loaders run, they search the “a” slice of the boot partition for a **boot.config** file (as a result, slices which are missing an “a” partition require user intervention during the boot process). If the **boot.config** file is found, its contents are used as the default configuration options for the boot block code and are echoed to the system console.

A valid format of this file is to put BIOS drive number, a controller type, a unit number, a partition, a kernel file name, and any other valid [boot(8)](/boot/8.md) option on a single line, as it is done at the “boot:” prompt.

The options related to the boot image selection described below and all the other options available for **boot.config** are documented in detail in the [boot(8)](/boot/8.md) manual page.

## FILES

- */boot.config*

  parameters for the boot blocks (optional)

- */boot/config*

  alternate location for boot config information

## EXAMPLES

The command:

```
# echo "-P" > /boot.config
```

will activate the serial console of FreeBSD if no keyboard is present, otherwise video console will be used.

The command:

```
# echo "1:ad(1,a)/boot/loader" > /boot.config
```

will instruct the second stage of [boot(8)](/boot/8.md) on the first disk to boot with the third [boot(8)](/boot/8.md) stage from the second disk.

The command:

```
# echo "1:ad(1,a)/boot/loader -P" > /boot.config
```

will do both of the above.

## SEE ALSO

[boot(8)](/boot/8.md), [loader(8)](/loader/8.md)

## AUTHORS

This manual page was written by Daniel Gerzo ⟨*danger@FreeBSD.org*⟩.