inode numbers

[Henry Spencer]

> On at least some European V7 systems, inode 1 is used for a list of bad
> blocks. Basically mkfs has been extended to include a secret undocumented
> option (in the true Unix tradition!) which scans the whole device and puts
> any funny blocks in inode 1 out of harms way.
> ...
> I have no idea whether this feature is standard (but undocumented), or a
> local hack, but I have seen it on more than one system.

It's sort of semi-standard.  The original V7 had hooks in mkfs for putting
a bad-block list in inode 1, but didn't bother actually doing it (the
give-me-a-bad-block-number routine was a stub that always returned "none").
Many people have noticed this and extended mkfs, in one way or another, to
actually install a bad-block list.

> As far as I know, nothing else
> pays any attention to the list - it is just a device for keeping blocks off
> the free list without upsetting fsck.

Actually, several other programs (e.g. dump and restor) needed slight fixes
to make them keep their hands off inode 1, but these were pretty trivial.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry