Subject: Re: [vserver] Using unionfs on guest root
From: Oliver Welter <mail@oliwel.de>
Date: Tue, 26 Aug 2008 09:48:06 +0200

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> I put the aufs mount in the guest fstab:
> none / aufs dirs=overlay:rootfs=ro 0 0
> 
>> that's the correct way to do it (fstab.remote for
>> network related mounts)
> 
> When I launch the guest, I get:
> vcontext(/dev/null) permission denied
> 
>> looks like your /dev/null is not accessible,
>> try to add an explicit 'dev' to the fstab,
>> IIRC, the fstab mounts are executed 'securely'
>> which means they add 'nodev' if not specified
>> otherwise ...
> 
> Anybody has a working setup?
> 
>> no, why would one do that, when there is something
>> like unification available, with a lot of advantages
>> over such an overlay setup ...
> 
I explained my setup here several times and I did not find a way to make
this work using unification.
The "share a common root" might work with unification but puts a bunch
of work on each update, as I have to care about config files and correct
packaging (what is not that easy in gentoo)

What definitily is not working, as far as I can think, is testing. With
the union approach I can upgrade a guest, mirror a set of test data into
it and kick it up to run some tests, if it works, I switch the overlay.

Besides - it puts an extra level of security to the system as you can
easily see writes to places where they should not happen.

But if anybody can point me to an easier setup, I will try hard.

Oliver


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