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Re: Readonly RootFS support in Emdebian

On Wed, 02 Feb 2011 23:02:23 +0100
Marcus Osdoba <marcus.osdoba@googlemail.com> wrote:

> I successfully followed the steps given in the Debian wiki [1] to come 
> over some restrictions to make debian work on a read only rootfs.
> [ ] RO support is not compliant with Debian architecture.

The way you've defined it, no. Debian follows the FHS and only
having /var/ readwrite is itself not compliant with FHS.

The ReadOnly wiki page explicitly extends read-write requirements
to /etc/, /home/, /srv/ and /tmp as well as /var/, so you have to use
some bindmounts anyway.

It also clearly documents the packages which require a writable /etc/
and has a few workarounds.

I'm not sure what you're expecting Emdebian to do. Using bind mounts to
allow writes into /srv and /home is not something that happens in the
packages, you need to sort that out in /etc/fstab. multistrap can put
that file in place using the setupscript option but as to what actually
goes into that file and how it works with other packages, that's not
down to the packages themselves.

Emdebian Grip has the same support for this as Debian - it requires
custom setups. i.e. hacks.

Most systems which would need a read-only fs would probably be better
with a smaller distribution. That's the question around Baked - it's so
far from what Debian can normally do that it's questionable whether it
actually is Debian anymore. A read only fs is a step beyond Baked.

There's no point using Grip for a read only fs because Grip implicitly
requires a writable fs, as does Debian. You're just wasting space if
you use Grip rather than Baked - all that code meant to allow smooth
upgrades and post-installation configuration (all the code that makes
Debian Debian) is just useless. Don't install it in the first place -
use Baked and create the entire configuration exactly as you want.
Emdebian can help with the tools but the actual content of any Baked
system - or read-only fs - is down to whoever wants that particular


Neil Williams

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