---
name: "cdboot"
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/cdboot"
---

# cdboot(8)

amd64-specific second-stage CD-specific bootstrap

## NAME

**cdboot** – amd64-specific second-stage CD-specific bootstrap

## DESCRIPTION

**cdboot** is a modified version of the amd64 second-stage bootstrap program, [boot(8)](/boot/8.md), configured to be run by the OpenBSD El Torito CD-ROM boot sector *cdbr*. **cdboot** will look for an */etc/boot.conf* configuration file on the CD-ROM. If it finds one, it processes the commands within it. *boot.conf* processing can be skipped by holding down either Control key as **cdboot** starts.

**cdboot** then sits in a loop, processing commands given by the user. It accepts all the commands accepted by [boot(8)](/boot/8.md).

If no commands are given for a short time, **cdboot** will then attempt to load an OpenBSD kernel from the CD. It first looks for the install kernel *bsd.rd* in the standard amd64 release directory (e.g. */3.6/amd64/bsd.rd*), then for */bsd*. It may be told to boot an alternative kernel, either by commands in the *boot.conf* file, or by commands typed by the user at the **boot\>** prompt.

## FILES

- */usr/mdec/cdboot*

  CD-specific second-stage bootstrap

- */etc/boot.conf*

  **cdboot** configuration file (read from CD)

## EXAMPLES

Boot the install kernel:

```
boot> bsd.rd
```

## SEE ALSO

[boot(8)](/boot/8.md), [boot\_amd64(8)](/boot_amd64/8.md), [mkhybrid(8)](/mkhybrid/8.md)

## STANDARDS

Curtis E. Stevens and Stan Merkin, *El Torito Bootable CD-ROM Format Specification*, Version 1.0, January 25, 1995.

## HISTORY

The **cdboot** program first appeared in OpenBSD 3.6.

## CAVEATS

By default, many CD creation programs restrict filenames to the MS-DOS 8.3 format. Unless this is changed, **cdboot** will not be able to read its boot.conf(8) file. For example, with [mkhybrid(8)](/mkhybrid/8.md) the **-l** option should be specified.

## BUGS

The **ls** command does not work on ISO 9660 (cd9660) filesystems, which are used on most CDs.