---
name: "boot"
section: "8"
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/boot"
---

# boot(8)

alpha-specific bootstrap

## NAME

**boot**, **boot.conf** – alpha-specific bootstrap

## DESCRIPTION

The main purpose of this program is to load the system kernel.

As described in [boot\_alpha(8)](/boot_alpha/8.md), this program is loaded by the SRM firmware and provides a convenient way to load the kernel. This program acts as an enhanced boot monitor for alpha systems, providing a common interface for the kernel to start from.

Basic operations include:

- Loading kernels from hard disk.

- Loading kernels compressed by [gzip(1)](/gzip/1.md).

- Providing an interactive command line.

The sequence of its operation is as follows: initialization, parsing the configuration file, then an interactive command line. While at the command line you have 5 seconds to type any commands, if needed. If time expires, the kernel will be loaded according to the current variable settings (see the **set** command). If the kernel load fails, a second attempt is made with the timeout increased by one second. The sequence of **boot** operations is as follows:

1. If the file */etc/boot.conf* exists on the filesystem in slice ‘a’ on the disk **boot** was loaded from, open and parse it. Lines beginning with the ‘#’ character, as well as whitespace at the beginning of lines, are ignored. The file may contain any commands **boot** accepts at the interactive prompt. Though default settings usually suffice, they can be changed here.

2. The header line

   ```
   >> OpenBSD/alpha BOOT [x.xx]
   ```

   is displayed to the active console, where *x.xx* is the version number of the **boot** program, followed by the

   ```
   boot>
   ```

   prompt, which means you are in interactive mode and may enter commands. If you do not, **boot** will proceed to load the kernel with the current parameters after the timeout period has expired.

By default, **boot** attempts to load the kernel executable specified in the SRM environment variable *boot\_file*, defaulting to */bsd* if not set. If it fails to find the kernel and no alternative kernel image has been specified, the system will be unable to boot.

## COMMANDS

The following commands are accepted at the **boot** prompt:

- **boot** \[*image*\] \[**-cdns**\]

  Boots the specified kernel image with any options given. If *image* is omitted, values from the **boot** variables will be used.

  - **-c**

    Causes the kernel to go into [boot\_config(8)](/boot_config/8.md) before performing [autoconf(4)](/autoconf/4.md) procedures.

  - **-d**

    Causes the kernel to drop into [ddb(4)](/ddb/4.md) at the earliest convenient point.

  - **-n**

    Causes the kernel to ask for the **root** device to use.

  - **-s**

    Causes the kernel to boot single-user.

- **echo** \[*args*\]

  Displays *args* on the console device.

- **help**

  Prints a list of available commands.

- **hexdump** *addr* *size*

  Show *size* bytes of memory at address *addr*.

- **ls** \[*directory*\]

  Prints contents of the specified *directory* in long format including: attributes and file type, owner, group, size, filename.

- **reboot**

  Reboots the machine by initiating a warm boot procedure.

- **set** \[*varname* \[*value*\]\]

  If invoked without arguments, prints a list of variables and their values. If only *varname* is specified, displays contents of that variable. If *varname* and *value* are both specified, sets that variable to the given value. Variables include:

  - **debug**

    Debug flag if **boot** was compiled with DEBUG defined.

  - **image**

    File name containing the kernel image.

  - **timeout**

    Number of seconds boot will wait for human intervention before booting the default kernel image.

## FILES

- */usr/mdec/boot*

  system bootstrap

- */etc/boot.conf*

  system bootstrap's startup file

- */bsd*

  kernel image

- */bsd.rd*

  kernel image for installation/recovery

## EXAMPLES

Boot the default kernel:

```
boot> boot
```

Remove the 5 second pause at boot-time permanently, causing **boot** to load the kernel immediately without prompting:

```
# echo "boot" > /etc/boot.conf
```

Boot the kernel named */obsd* in “User Kernel Configuration” mode (see [boot\_config(8)](/boot_config/8.md)). This mechanism allows for the explicit enabling and disabling of devices during the current boot sequence, as well as the modification of device parameters. Once booted, such changes can be made permanent by using [config(8)](/config/8.md)'s **-e** option.

```
boot> boot /obsd -c
```

## SEE ALSO

[gzip(1)](/gzip/1.md), [autoconf(4)](/autoconf/4.md), [ddb(4)](/ddb/4.md), [boot\_alpha(8)](/boot_alpha/8.md), [boot\_config(8)](/boot_config/8.md), [fdisk(8)](/fdisk/8.md), [reboot(8)](/reboot/8.md)

## HISTORY

This program was written by Michael Shalayeff for OpenBSD 2.1 on the i386 platform, and was later ported to the alpha platform.