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Re: [Emdebian] apt-get on embedded systems



On Tue, 21 Apr 2009 20:33:57 +0200
Hector Oron <hector.oron@gmail.com> wrote:

>   Are there any plans to create/modify an apt-get suitable for embedded
> systems? I mean without that much perl dependencies and without that
> oversized apt cache.

I'm assuming you mean something to run on the embedded system itself,
so that removing perl means removing the perl-based maintainer scripts
and all associated perl support from the installation process. apt-get
doesn't need perl - what apt downloads tends to need perl. i.e. you
aren't looking to simply replace apt, you need to remove perl from
every stage of the Debian process, which is what Crush tries to do.

dpkg doesn't need perl either, no directly. perl only comes in from the
utilities called by maintainer scripts and by packages themselves.

The standard Debian busybox package cannot deal with these issues, it
needs to be reconfigured and then rebuilt - as in Crush.

As far as the size of the apt cache is concerned, Grip has that problem
solved - filtering the archive.

>   Would it be better to use other package managers (ipkg based)

ipkg and others are what Familiar used to use but the Debian packages
need to be modified to work with ipkg instead of apt and dpkg, then
modified again when the next Debian version arrives and again and again.
There is no way of reliably substituting apt and dpkg for replacements
without requiring massive changes to a whole range of package
installation scripts in standard Debian packages and then maintaining
those changes across each new version of the standard Debian package.
The changes are large enough when just replacing coreutils with
busybox and trying to remove perl. The changesets could become
unmanageable if layers for dpkg and apt replacement compatibility are
added as well.

This is one reason why Crush is so hard to do - we are breaking some
very fundamental assumptions within Debian and then expecting it to
continue behaving like Debian.

> or is it
> worth the effort to have an apt tool more thought to work on embedded?
> Maybe it is posible to add an apt-get->busybox. :-)

busybox dpkg is not particularly compatible with Debian dpkg, although
things are probably better in the versions of busybox that
Debian-Installer haven't used yet. :-) It's still always playing
catch-up with the real dpkg.

The problems with an apt replacement are:
1. Reliably making the same dependency choices as apt and/or aptitude.
2. Working with a dpkg replacement that doesn't quite behave as dpkg
behaves
3. Keeping up with the changes in apt and dpkg and Debian Policy
4. Tying all that with the changes needed in the packages themselves
related to the other changes you want, like removing perl.

If mini-perl becomes possible, then there are a whole new set of
possible compatibility issues.

-- 


Neil Williams
=============
http://www.data-freedom.org/
http://www.nosoftwarepatents.com/
http://www.linux.codehelp.co.uk/

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