U5 firmware password?

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

I've got a U5 which seems to have a password set in the OBP - a break
during the memory selftest results in an old-mode prompt

Type boot , go (continue), or login (command mode)
> 

and when I try "login", it wants a "Firmware Password", which of course
I don't have.  (I got this machine years ago and am only now trying to
do something useful with it - this is the same U5 I mentioned a few
weeks ago, which I now have some RAM for - thank you, sr@!)

Perhaps fortunately, if I disconnect the disk, it tries to netboot.  So
I pointed it at a 3.1 sparc64 netboot setup, and I have it up
single-user.  But eeprom says "property `security-mode' not yet
supported"; I can't set it to none.

The disk appears to have Solaris on it, so I thought I'd just null out
its root password and use that.  But when I fsck and mount it from
NetBSD (3.1, at least, that being what's in the netboot setup) I can't
seem to write to it; for example, with the Solaris disk on /mnt,

# cp /mnt/etc/shadow /mnt/etc/SAVE.shadow.SAVE
cp: /mnt/etc/SAVE.shadow.SAVE: File too large

even though the file is by no means large.  (This even after fsck
passed the filesystem.)

So, any suggestions?  Am I doing something stupid here?  Does sparc64
have security-mode support in newer releases?  (I'd rather not go
through setting it up only to find out it doesn't help.)

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