[rescue] SGI Indy revival

[Mouse]

> I am hoping to show an Indy [...] make sure it is fully backed up
> first, [...]

> Here is the process I'm thinking, and I'd like feedback on it.

> 1) Boot into single user mode.

> 2) Connect a second disk and EFS format it.

> 3) Use tar to backup the first disk  piped to tar extract on pointed
> at the new disk.

> 3b) tar -cpofv - -C / . | tar -xpof - -C /newdisk

> I'm a little uncertain if it will then end up trying to recursively
> stuff as it is written to /newdisk.

Probably.  Many tars have no way to say "archive this directory but
don't include this subdirectory thereof".  Mine does.  Sometimes I've
used it.  Other times I've used other tactics.  For example, in some
cases I've created a new partition on the old disk that exactly
overlaps the partition I want to copy, mounted that new partition
read-only, and copied out of it.  (Of course, this works only if the
old partition is also read-only, as writing to the filesystem via one
mount while reading from the other is a recipe for fireworks.)  This
depends on a whole bunch of things, things which may or may not be true
of Irix (I don't know it well enough to say).  I do it only on NetBSD,
on which it's possible to create a partition in the live system without
creating it on the disk.

I would offer the thought that, for some purposes, it would be better
for the new disk to be enough bigger than the old that you can make an
image of the whole (old) drive on the backup drive.  It would be
something like

3) Use dd to copy the first disk onto the second:

dd if=/dev/WHATEVER bs=65536 of=/newdisk/olddisk.img

(65536 can be pretty much any multiple of 512 in that general range.
Too small and the per-syscall penalty becomes a performance killer; too
large and lack of parallelism becomes a performance killer.  Among my
tools is one that forks, using memory shared between the processes for
very fast transfer of data, with one process reading and the other
writing, to get faster copies in cases like this.)

However, given what you said below, it sounds as though you want the
new disk to be bootable.  What I've sketched above won't give you that.
See below.

> 4) turn off, unplug, swap the scsi ID on the new disk to the old one
> and disconnect the old one.

If you want to be able to do this with a direct disk image, you need to
copy to the new disk directly instead of to a file in a filesystem on
the new disk.  Use the new disk device in the of= clause above for
that.

Some OSes will be just fine with a filesystem-level copy such as your
tar would create.  I don't recall enough Irix to know whether it is
one.  But if your new disk is larger than the old, or (even better) is
exactly the same size, then a dd-style copy from the old disk to the
new stands a decent chance of giving you a running system.

If you go with a filesystem-level copy, there may be bootblocks or some
such that needs copying separately.  I don't think I ever knew Irix
well enough to know whether it had sny such.

If you don't need the new disk to be bootable per se, but just want to
be able to restore, then you could put the old disk and the new disk on
a machine with a boring but well-known OS, like a BSD or Linux, and use
its filesystem and my modified step 3 above.  Then, if you need to
restore, just put them both on the same OS again and redo the dd,
except swapping if= and of=, to write the image back onto the disk.

/~\ The ASCII				  Mouse
\ / Ribbon Campaign
 X  Against HTML		mouse at rodents-montreal.org
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B