Re: Hiding nodes with unionmount

[Arne Babenhauserheide]

Hi Fredrik, 

Am Donnerstag, 30. Juli 2009 10:48:00 schrieb Carl Fredrik Hammar:
> A cleaner solution would be to first mount a hypothetical ``filterfs''
> that removes the files, and then do a unionmount on top of that.  Also you
> could just simply set a lib.so.1 -> lib.so.3 symlink in the mountee, which
> would shadow the underlying lib.so.1.

That's definitely sounds cleaner. 

Could a filterfs and unionmount be combined to a fully transparent writeable 
filesystem which uses a readonly filesystem as base? 

That way I could use a LiveCD as base and store my changes on a USB-stick. To 
setup my environment (including my user data) I'd just set my "this is my 
system" translator on root. 

$ settrans -a / mine /mnt/usb/arne.tbz

Other users would still see the original system, but I'd work in my own 
environment. 

Puppy Linux does something similar with its layered filesystem, but I think 
translators should be able to provide the same with much more flexibility. 

It could even use a version tracking backend, which tells it which files need 
to be filtered and added. That way a change in the base system could be 
reflected in the filterfs. This would then use a lot more space, but if the 
main repository would be used as a base by all users, that space would only be 
required once. 

Instead of that it could also just access an installed package database for 
filtering installed programs - in Gentoo that would just mean accessing the 
files inside /var/db and telling the filterfs (or a preprocessor) not only to 
mask files but to mask installed packages so they can get replaced completely 
by the users installed packages. 

I could have a Gentoo where every user can modify the whole system without 
affecting any other user. 

Best wishes, 
Arne

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