Is there a BSD operating system that can be booted off a logical drive partition?

Question

From several BSD operating systems' documentation, there is a requirement for it to be booted off a primary partition. Is there any BSD that can be booted off a logical partition in some indirect manner? If not, what is/are the technical reason(s)?

Answer 1

I can think of three hurdles:

• The OS itself. As far as I know, this not a problem, since all BSDs store their own partition table (the a, b, c, … partitions) independently from the PC partition table (the slices in BSD terminology).

• The bootloader. This can be a problem, because bootloaders operate under very tight code size constraints, and every feature is an added burden. But once the bootloader gets to the point where it reaches the BSD partition data, you've won. Grub can boot a number of BSDs, but not all versions of Grub can boot all versions of *BSD.

• The installer. Here there's no significant size constraint, but supporting logical partitions does add to the complexity. Still, even if the installer automation doesn't support it, you might get somewhere by issuing the right shell commands at the right time.

Looking at specific variants:

• FreeBSD: The installation manual is silent on the topic. There is a success report; see also this discussion.

• NetBSD: The installation manual states that “NetBSD installs in one of the four primary BIOS partitions”. Supposedly you can install and boot on a logical partition, if you figure out how.

• OpenBSD can boot on a logical partition since 4.4, though the installation manual says that “extended partitions may not work”.