RPM filesystem?

[Doncho N. Gunchev]

On 2004-06-03 (Thursday) 17:31, Tim Daly wrote:
> a simple question: why unpack RPMS? Clearly Linux itself can be run
> compressed (Live CDs do that now). Given the bottleneck of slow disk

    Live CDs based on konppix do use compressed ISO image, which is a
FS, the compression comes from the cloop kernel module (compressed
loop) which transparently makes it look like an usual block device.

> and fast CPU it might be faster to load the compressed image, unpack
> it, and execute it then it would to load it directly. Yet another 
> feature is that RPMS don't have to explode all over the filesystem
> so upgrading is just a copy operation. Is anyone aware of an effort

    You'll have to mount somehow them. What will it look like to have
say 500-1000 'mounted' packages?

> to make an RPM filesystem? Could such a filesystem run in user space?
> 
> RPMS might not be the very best format for compressed packages but
> they could make a convenient starting point. Fedora extras would
> be so much sweeter if you only needed to mount the DVD containing
> the RPMS and it all "just worked".
> 
> Tim Daly
> axiom at tenkan.org
> daly at idsi.net
> 
> 

    There are other things that are designed and convenient for this purpose
like cloop. Even if the problem with the configuration files and /log and
even /var is solved, it is still too inconvenient to unpack the whole archive
just to read the file that's on it's end. If I understand the compression
right, there's no way to start decompressing a rpm package from the middle.
AFAIK rpm is gzipped cpio archive with headers, check the script at 
http://www.rpm.org/tools/scripts/rpm2cpio.sh if you care. Your idea could
work if each file was individually compressed, which will not be advisable
for rpm because this will lower the compression ratio.
    I was thinking of something opposite one day - what about if the first
fedora CD is a cloop image like knoppix and all rpm packages can be 'restored'
from it and directly installed on the disk? The main problem I see is that
the GPG sign of a rpm package is calculated from it's compressed image (please
correct me if I'm wrong). No one can guarantee that when recreated from the
installed files and compressed the GPG sign will match it any more. If the
sign is calculated from it's uncompressed image this could work...
    I don't say this is not possible, I just think it's inadvisable.

    I'll ask someone more familiar with the rpm package format to correct me
if I'm wrong at some point.

-- 
Regards,
  Doncho N. Gunchev    Registered Linux User #291323 at counter.li.org
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