Re: [Devil-Linux-discuss] DL configuration/Unionfs

[Dick M. <di...@li...>]

Bruce,

>>>>> unionfs is a part of DL 1.3

> I like the idea, but I've never used unionfs.  The docs for unionfs seem
> to be kind of scarce.  Can you post some examples of how you use it?

yes it's a bit obscure.  (http://www.linuxjournal.com/article/7714). Reading 
around apparently unionfs has a poor reliability reputation. There's a fork call 
aufs which does the same only more stable, faster etc etc. 
(http://aufs.sourceforge.net/). That's actually what I'm using on my desktop.

> If I understand your suggestion before, the /etc directory would be
> un-tar'ed on the CD.  Then a unionfs in memory would be a branch above
> it and all the additions/changes are made there?

Yes, exactly.  The /shm/etc/would be a union of itself and the etc-default.

You do it like this:

mount -t unionfs -o dirs=/shm/etc:/etc-default=ro none /shm/etc

(note:  substitute aufs for unionfs above if you choose that).

Magically etc-default appears in /shm/etc and you can edit and delete file as 
well as add new ones.  I.e untar your own config files into it.

> How do we modify save-config to only save the changes in the upper
> modified branch? 

That's the tricky bit - problem with above config is you'd have to umount 
etc-default to be able to see just the difference files.  Not so good.

You could have 2 directories:  /etc-default and /shm/etc-admin and mount like this:

mount -t unionfs -o dirs=/shm/etc-admin:/etc-default=ro none /shm/etc

Then /shm/etc would look as above but you can also see just the admin changes in 
etc-admin.

That might be better.

> Can we just save that directory?  (I need to play with
> unionfs, except it's not included in my 1.3 either :)

both unionfs and aufs are std in Debian if you've got a deb desktop.

> Another advantage of doing this is the size of the config file saved to
> the floppy/usb would be a LOT smaller!

Yes indeed.

Dick