[clug] UnionFS based package management system: good idea or fatally flawed?

[Scott Ferguson]

 On Sat Aug 28 19:42:12 MDT 2010 steve jenkin
sjenkin_at_canb.auug.org.au wrote:
> In my wild, erratic stumble across the deserts & jungles of the
> InterWebs, came across this yesterday on the LFS, Linux From Scratch site.
>
> This approach is how "Plan 9" might do things, and a nice wrinkle could
> be using ISO images, squashfs or crypto-signed blobs to house 'units of
> change'. Solves some problems, creates others.
>
> There's a question I had and STFW'd, but couldn't find a good answer...
>
>  - How big is the performance hit (and RAM needed?) for an Overlay/Union
> mount.
>
>  - Normal systems need to support ~5,000 packages, could this approach
> scale?
>
> cheers
> steve
>
> [In "Plan 9", there's a single /bin and /lib. You overlay mount
> everything you need onto them.]
>
>
> <http://www.linuxfromscratch.org/hints/downloads/files/pkg_unionfs.txt>
> <snip>
> </snip>
> HINT.
>
> This type of package management is inspired by GoboLinux's unique take
> on the archaic Unix directory structures*. Instead of installing all
> packages into the /usr directory whose contents can become quite
> unwieldy, packages are installed into their own directories.
>
> -- 
> Steve Jenkin, Info Tech, Systems and Design Specialist.
> 0412 786 915 (+61 412 786 915)
> PO Box 48, Kippax ACT 2615, AUSTRALIA
>
> sjenkin at canb.auug.org.au http://members.tip.net.au/~sjenkin

*Good Idea?
_If_ you are building your own distro using multiple packaging systems
(eg. .tgz, rpm, apt etc) it has great potential (if mounted at boot time).
If you are a "user" wanting to add additional packages to a running
system.... conditionally (more choices). All the problems of extra
desktop bling.
For an "average" already running system alien would "probably" be less
difficult to maintain a mixed package management system.

*Fatally flawed?
I'm not qualified to even venture an opinion on that. It would normally
only be used during the building a machine, not while running it. :-)

*How big is the performance hit (and RAM needed?) for an Overlay/Union
mount?
Conditional - how big is the file system you plan on mounting??

*Normal systems need to support ~5,000 packages, could this approach
scale?
Yes. However 20,000+ packages would be a better capacity starting point.

Note: the attribution to GoboLinux seems to overlook the GNU Universal
Package Manager and parts of LSB... :-/

Cheers