Date: Thu, 3 Oct 1996 09:25:47 -0400 From: der Mouse <mouse@Holo.Rodents.Montreal.QC.CA> To: hackers@freebsd.org, tech-kern@NetBSD.ORG Subject: Re: VPS mailing list, BSD interest? Message-ID: <199610031325.JAA06096@Collatz.McRCIM.McGill.EDU>
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> How can you have an LFS root partition (never mind the LVM stuff), > and still be able to boot on, say, a Sun3? Perhaps you can't, which would mean only that you can't have an LVM root on a sun3. > I mean, doesn't the boot prom have to be able to read the file system > to load the loader program? No. > Where are you going to stuff boot.sun3? Now, I don't know about other machines, but the sun3 I do know a bit about. (This also is true of the sparc, at least all sparcs I've ever looked at the boot mechanisms of.) The PROMs know enough about the disklabel to locate the start of the desired boot partition. They then load a bootstrap from the beginning of that partition (sectors 1 through 15, IIRC) and hand control over to it. The PROMs don't know a thing about the filesystem. That knowledge is all in later-stage bootblocks. In the NetBSD paradigm (and in more recent SunOS - 3.5 was the last SunOS I used that didn't work this way), the bootblock loaded by the PROM just has a list of disk block numbers wired into it, set by installboot when the bootblock was installed. It loads these blocks, trusting that they're the correct ones. _That_ program knows enough about the filesystem to load /netbsd (/vmunix under SunOS). In short, provided we stick with mostly-SunOS disklabels, the sun3 and sparc ports can use damn near anything for a root filesystem layout, as long as someone writes bootblocks that can grok it. der Mouse mouse@rodents.montreal.qc.ca 01 EE 31 F6 BB 0C 34 36 00 F3 7C 5A C1 A0 67 1D
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