In messages <http://marc.info/?l=openbsd-misc&m=128731581124975&w=1>
and <http://marc.info/?l=openbsd-misc&m=128731706126612&w=1>, I wrote
quoted text
> My primary laptop ("nitrogen") died, so I moved its disk to a backup
> laptop ("oxygen").  That laptop then died. :(  I have now moved the
> former-nitrogen-disk to an external enclosure so that I can access my
> files via USB from still another laptop ("silver").
> 
> When I connect the USB cable to silver I see the usual dmesg lines.
> But the former-nitrogen-disk contents are "wierd":
[[...]]

I'd like to thank all those who responded, both on the mailing list
and by private E-mail.

I eventually determined that the problem was the external enclosure
(labelled 'Rocketfish RF-PHD25 2.5" Enclosure kit for hard drives').
When I took the disk out of the external enclosure and put it back in
oxygen,
	[nitrogen is at the repair shop, but oxygen only
	crashes "occasionally"]
it worked perfectly: it passed fsck on all partitions (including an
svnd-encrypted one), and oxygen even stayed up long enough for me to
rsync the latest version of /home to a spare laptop (to which I'd
previously restored a week-old backup).

I don't know whether the external enclosure is just poorly made, or
whether the disk needed more power than the USB ports on the spare
laptop could provide.

Key lessons learned for the future:
1. Backups.  Lots of them.  Tested to ensure they're readable.  And
   done frequently so minimum work is lost if you have to recover
   from them.  (In this case I had all but the last of these -- my
   normal routine is to backup every 3-4 days, but due to various
   work crises I'd let a full week elapse.  Bad Jonathan.....)
2. Spare disk partitions.  The last time I set up a windoze laptop
   for my wife, I left a spare partition.  That made it easy to set
   up silver...

ciao,

-- 
-- "Jonathan Thornburg [remove -animal to reply]" <jthorn@astro.indiana-zebra.edu>
   Dept of Astronomy, Indiana University, Bloomington, Indiana, USA
   "Washing one's hands of the conflict between the powerful and the
    powerless means to side with the powerful, not to be neutral."
                                      -- quote by Freire / poster by Oxfam