Re: [gentoo-osx] New document: Project targets

[Dirk Schönberger]

Hi,

I just wanted to open for discussion another idea I've got to solve the
problem of having to update a system with a fixed set of pre-installed
components, aka the "Gentoo for OSX" problem.
I would like to avoid the prefixed approach (which seems to need changes
in the system software, i.e. the Portage system).
Instead i would like to solve the problem on a lower level.

A (Linux) LiveCD distribution faces a similar problem, because you have a
amount of static / read only content on your CD, while you are still able
to install packages from the internet.
Such Live CDs solve this by the introduction of "read-write" mounted
CD-ROM devices, using a mechanism called a "union file system". Such a
Union file system (unionfs) provides a unified view from a couple of
source trees to a result tree. THis applies to all file system accesses,
i.e. read, write, list directory a.s.o..

A unionfs is supported natively by MacOSX.

A problem of such an approach is that mounted file systems are visible
globally. A better solution would be a file system which is only visible
in a local environment.
Unfortunately real user space per process file systems are not yet
available on Unix like sstems, including Linux and Darwin / MacOSX.

For Linux there exist some work to implement such functionality, e.g. in
the Plasticfs project on Sourceforge. It seems to be implemented as some
kind of clever LD_PRELOAD hack.

Regards
Dirk


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