[one-users] Restarting a vm instance after shutdown?

[Lars Kellogg-Stedman]

Steffen, Tino,

Thank you both for your answers.  Using persistent disk images (or the
"save as" feature) helps a little bit, but what I was really hoping
for was a model in which:

(a) A vm instance would start with its own copy of a disk image.
(b) Shutdown would not delete the image.
(c) Some command (restart, or resubmit, or something) would allow one
to restore a vm instance that had been shut down.
(d) Disk data would only be discarded with an explicit "delete".

Ideally, this would be controlled at the virtual machine level, not
the disk image level.  That is, one would set the "don't delete on
shutdown" option on the vm instance.

The problem with "persistent" images is that -- as far as I can tell
-- the vm instance references the image in the repository directly,
rather than getting "private" persistent *copy* of the image.  The
problem with "saving" a vm instance is that it doesn't really address
the problem of, "whoops, I typed the wrong vm id and shutdown the
wrong system".  It also forces the template description file to become
more important, since the "recovery" process is to create a new
virtual machine instance, rather than rebooting the old one.

I have seen several similar questions on the list from folks looking
for a way to support persistent virtual machines, so it looks as if
this is a model for which there is some demand.  For those of you
familiar with the codebase, does this look as if it would be hard to
implement?  If I wanted to implement it myself, should I be looked at
the 2.4 code?  We're running 2.2 locally, but I understand that 2.4 is
on the horizon.

-- 
Lars Kellogg-Stedman <lars at seas.harvard.edu>
Senior Technologist
Harvard University SEAS
Academic and Research Computing (ARC)