On 01/07/2011 03:18 PM, Grégoire Sutre wrote: > On 01/07/2011 13:20, Vladimir 'φ-coder/phcoder' Serbinenko wrote: > >>> Do you know of any OS that would put the superblock in sector 0? >>> I googled a bit, but I couldn't find examples where UFS would >>> not start with a boot sector (afaics, it usually starts with a >>> bootblock area of at least 8KiB -- with OS-specific data in it, >>> e.g. a disklabel). >>> >> According to *BSD http://fxr.watson.org/fxr/source/ufs/ffs/fs.h: >> >> */"* Depending on the architecture and the media, the superblock may/* >> */* reside in any one of four places. For tiny media where every >> block /* >> */* counts, it is placed at the very front of the partition. >> Historically,/* >> */* UFS1 placed it 8K from the front to leave room for the disk label >> and/* >> */* a small bootstrap. For UFS2 it got moved to 64K from the front to >> leave/* >> */* room for the disk label and a bigger bootstrap, and for really >> piggy/* >> */* systems we check at 256K from the front if the first three fail/*" > > Interesting. So, when searching for a UFS superblock, sector 0 is a > candidate (after sectors 128 and 16). It seems to me that this use of > sector 0 for tiny media does not apply to (recent) NetBSD newfs(8), > though. > > If we want to improve the situation, we could let the filesystem driver > dynamically decide whether the first sector is reserved or not. But > I'm not sure that it's worth it (the first sector of a partition > containing a filesystem is only used for blocklist embedding, right?). > It's used for putting boot.img into partition. But you're right, it's used mainly for blocklists installs. > Grégoire > > _______________________________________________ > Grub-devel mailing list > Grub-devel@gnu.org > http://lists.gnu.org/mailman/listinfo/grub-devel >
-- Regards Vladimir 'φ-coder/phcoder' Serbinenko
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