---
name: "loader.4th"
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/loader.4th"
---

# loader.4th(8)

loader.conf processing tools

## NAME

**loader.4th** – loader.conf processing tools

## DESCRIPTION

The file that goes by the name of **loader.4th** is a set of commands designed to manipulate [loader.conf(5)](/loader.conf/5.md) files. The default */boot/loader.rc* includes **loader.4th** and uses one of its commands to automatically read and process the standard [loader.conf(5)](/loader.conf/5.md) files. Other commands exists to help the user specify alternate configurations.

The commands of **loader.4th** by themselves are not enough for most uses. Please refer to the examples below for the most common situations, and to [loader(8)](/loader/8.md) for additional commands.

Before using any of the commands provided in **loader.4th**, it must be included through the command:

```
include loader.4th
```

This line is present in the default */boot/loader.rc* file, so it is not needed (and should not be re-issued) in a normal setup.

The commands provided by it are:

- **boot**

  - **boot** *kernelname* \[**...**\]

  - **boot** *directory* \[**...**\]

  - **boot** **-flag** **...**

  Boot as specified by the [loader.conf(5)](/loader.conf/5.md) files read.

  Depending on the arguments passed, it can override boot flags and either the kernel name or the search path for kernel and modules.

- **boot-conf**

  - **boot-conf** *kernelname* \[**...**\]

  - **boot-conf** *directory* \[**...**\]

  - **boot-conf** **-flag** **...**

  Works like **boot** described above, but instead of booting immediately, uses **autoboot**, so it can be stopped.

- **start**

  Reads */boot/defaults/loader.conf*, all other [loader.conf(5)](/loader.conf/5.md) files specified in it, then loads the desired kernel and modules (if not already loaded). After which you can use the **boot** or **autoboot** commands or simply exit (provided *autoboot\_delay* is not set to NO) to boot the system. **start** is the command used in the default */boot/loader.rc* file (see [loader(8)](/loader/8.md)).

- **initialize**

  Initialize the support library so commands can be used without executing **start** first. Like **start**, it reads */boot/defaults/loader.conf* and all other [loader.conf(5)](/loader.conf/5.md) files specified in it (but does not load kernel or modules). Returns a flag on the stack to indicate if any configuration files were successfully loaded.

- **read-conf** *filename*

  Reads and processes a [loader.conf(5)](/loader.conf/5.md) file. Does not proceed to boot.

- **enable-module** *module*

  Enables the loading of *module*.

- **disable-module** *module*

  Disables the loading of *module*.

- **toggle-module** *module*

  Toggles the loading of *module* on and off.

- **show-module** *module*

  Shows the information gathered in the [loader.conf(5)](/loader.conf/5.md) files about the module *module*.

- **retry**

  Used inside [loader.conf(5)](/loader.conf/5.md) files to specify the action after a module loading fails.

- **ignore**

  Used inside [loader.conf(5)](/loader.conf/5.md) files to specify the action after a module loading fails.

- **try-include** *file* \[*file ...*\]

  Process script files if they exist. Each file, in turn, is completely read into memory, and then each of its lines is passed to the command line interpreter. If any error is returned by the interpreter, the try-include command aborts immediately, without reading any other files, and silently returns without error.

## FILES

- */boot/loader*

  The [loader(8)](/loader/8.md).

- */boot/loader.4th*

  **loader.4th** itself.

- */boot/loader.rc*

  [loader(8)](/loader/8.md) bootstrapping script.

- */boot/defaults/loader.conf*

  File loaded by the **start** command.

## EXAMPLES

Standard */boot/loader.rc*:

```
include /boot/loader.4th
start
```

Load a different kernel with the standard configuration:

```
set kernel="kernel.old"
unload
boot-conf
```

Read an additional configuration file and then proceed to boot:

```
unload
read-conf /boot/special.conf
boot-conf
```

Disable the loading of the splash screen module and bitmap and then proceed to boot:

```
unload
disable-module splash_bmp
disable-module bitmap
boot-conf
```

## SEE ALSO

[loader.conf(5)](/loader.conf/5.md), [loader(8)](/loader/8.md)

## HISTORY

The **loader.4th** set of commands first appeared in FreeBSD 3.2.

## AUTHORS

The **loader.4th** set of commands was written by Daniel C. Sobral ⟨*dcs@FreeBSD.org*⟩.

## BUGS

A British espionage series.