I've got Ubuntu Breezy installed here (5.10) on my PegasosII since years.
Last week I've been met with nasty messages at boot time while
checking root filesystem warning me about multiply-claimed blocks shared by different files.
It tries an automatic fsck and fails suggesting a manual fsck and tells
that for this reason root is currently set to read-only (to be restored with "mount -n -o remount,rw /").
At this point i'm given back control of the console input BUT
the keyboard stops working and i'm left with a blinking cursor.
(Bash says it can't find lesspipe and dircolors before issuing such a prompt), any step-by-step help?
(something more detailed than simple "Use Mupper!")

Try to use fsck for MorphOS, just a blind try :).
http://home.elka.pw.edu.pl/~mszyprow/pr ... k-1.39.lha

That would be a good plan.

It sounds like the partition is really trashed, though. Fixing it enough to make it mount may not bring back important files needed to boot (if bash complains like that, you're in trouble for sure!)

It may be better to salvage as much as you can using MorphOS or even a rescue image from an installation CD (try the SuSE one, front page of this site) and then go for broke and just format the whole thing and start again.

Nice idea, actually I suppose I would need first to mount the partition with the morphos Ext2 driver but it doesn't work for me (it didn't work even when it was a "good" partition) not even with help from Giggledisk, I place the Linux mountlist in Devs:dosdrivers/ but it doesn't mount it (no feedback at all from Peg), even if I move the aforementioned mountlist somewhere else and make a reboot I'm told that the object already exists :shock: .

If you have Morphos 2.1 installed you can try with Mounter tool (you'll find it in SYS:Tools directory). This nice stuff (tnx Morphos-Team for it) allow you to mount several kind of partitions on boot, after boot, unmount them or create a mountlist for each of them.
Bye,
AKiLL