[kwlug-disc] Can OSs demand too much?

Chris Frey cdfrey at foursquare.net
Fri May 14 22:53:33 EDT 2010


On Fri, May 14, 2010 at 10:06:52PM -0400, unsolicited wrote:
> >But upgrading is not a "fire and forget" experience.  The last time
> >I did it, I actually created a VM of the system and did a trial run
> >first.  That sure helped flush out any issues beforehand, while keeping
> >the system in a useable state.
> 
> That's interesting. How did you go about doing that / what's the 
> easiest way to do so?

I forget exactly how I did it, but it was basically:

	- create a large sparse file as your disk
	- format it with filesystem of choice
	- loopback mount it
	- copy the host system's directories, except home, minus anything
		else that's huge
	- unmount it, and then tack on a boot sector to the front
		and setup the boot sector in the file with fdisk
	- use the file as your disk in the VM, and boot a rescue CD
	- run grub or lilo to make it bootable

There would be peculiarities particular to your system, of course.

Once you have your host system duplicated in your VM, then you just follow
the upgrade documentation for your distro of choice (Debian is pretty
good about that), and document any special steps you had to do to solve it. 
At that point, you have all you need to do a successful, real, upgrade.



> With apologies, sounds like something a lot of people would like to 
> know, and see. (-:

:-)

Setting up the VM copy might be worth a blog post.  It's easier to
follow documentation for tricky technical things like this than a
presentation.

But in the end, it's all just files.  Things have gotten more complex
lately with udev and initrd, etc.  But the old unix way is still turtles
all the way down -- I mean, everything's just a file.

- Chris




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