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CDBOOT(8) System Manager's Manual (amd64) CDBOOT(8)

cdboot
amd64-specific second-stage CD-specific bootstrap

cdboot is a modified version of the amd64 second-stage bootstrap program, boot(8), 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).

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.

/usr/mdec/cdboot
CD-specific second-stage bootstrap
/etc/boot.conf
cdboot configuration file (read from CD)

Boot the install kernel:

boot> bsd.rd

boot(8), boot_amd64(8), mkhybrid(8)

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

The cdboot program first appeared in OpenBSD 3.6.

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) the -l option should be specified.

The ls command does not work on ISO 9660 (cd9660) filesystems, which are used on most CDs.
March 30, 2016 OpenBSD-current