SunOS 4.x boot disk layout

Patrick Finnegan pat at
Sun Mar 27 09:51:57 CST 2005

On Sunday 27 March 2005 07:12, Jules Richardson wrote:
> However, obviously some space is taken up by the partition table
> itself, so the first (root) partition can't start at block zero. What
> I'm trying to find out is the offset that it does actually start at,
> so that I can mount the root partition from Linux.

Actually, the root partition does start at sector 0.  With a sun disk 
label, it's always on sector 0, and usually overlaps with the first 
partition.  Thus, the filesystem is supposed to not occupy the first 
sector of its partition, which is the same for how PCs work (the first 
sector is usually called the 'boot sector' in PC land; in Sun land, the 
partition table/disk label and 'boot sector' can overlap, as there is 
no 'master' boot sector for the disk (ala the PC's MBR), thanks to the 
intelligence of the Sun's boot prom).

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