While tracking down a distribution ordering problem in dpkg-http, I
realized that there are several different behaviors that people might
want, depending on the stability/features they want and their distrubiton
sources. I thought a list of these behaviors would be useful for the
apt/deity team and dpkg-* maintainers.
1) Packages come from the last distribution in which they are available.
Most useful for tracking multiple distributions (stable/unstable). For
regular users desiring stability but some unstable-only packages the order
is unstable,stable. For developers early in the release cycle running all
the unstable packages that exist the order is stable,unstable.
2) Highest version wins regardless of distribution order.
Useful if you have a slightly-obsolete CDROM/local archive and a slow
ftp link to a current distribution. Useful for tracking a single
distribution (hamm for instance) where you have most of the packages
nearby, but want remote updates. eg. silver CD plus stable ftp point
releases. Most useful for those desiring high stability with important
patches (stable+point releases).
3) Later-overrides-earlier unless the installed version is higher than the
version from the distribution.
If you order the packages (experimental, unstable), packages will track
unstable by default, *unless* you install a higher version from
experimental, in which case experimental will be tracked for that package
only. Useful for both bleeding-edge developers (experimental,unstable)
tracking a few packages from experimental, and for users tracking stable
with a vew unstable exceptions. Order (stable,unstable) behaves the same
as method 1.
So there are three different distribution-selection algorithms. dpkg
--merge-avail currently implements the first of these. dpkg-http had an
unfortunate mix of method 1 & 2, and now implements method 3 ( v0.13 from
http://biocomp.anu.edu.au/~dld/debian/ only for the moment). Method 2 is
unimplemented unless apt or dftp can do this. Method 2 may be the largest
Being able to combine methods might also be useful for some users.
CDROM of stable, ftp to a stable-point-release site, and tracking a few
Dr. Drake Diedrich, Research Officer - Computing, (02)6279-8302
John Curtin School of Medical Research, Australian National University 0200
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