On Thu, 22 Apr 2004, Yann Dirson wrote: > You're right, it unpacked the version from the cache. But then there is > still a bug in apt, since unless I clean the cache, it will continuously > unpack it, thinking it is the right deb.
This is how it is designed to work.. Undesirable, but you violated an invarient it depends upon. Once a package makes it out of the partial directory APT never rechecks its md5sum. It assumes that the tuple (package,version,arch) is sufficient to map metadata from the Packages file onto metadata from a cached deb. It does a quick check of the .deb size against the Packages file and then assumes it is the .deb that is described, even if it isn't. It also CRCs the metadata and produces seperate internal representations for (package,version,arch) tuples that have different CRCs. So, whenever it goes to lookup something in the cache it internally could think it is any one of the three 0.7.3-1 versions your APT knows about. This whole fragile scheme is designed to seamlessly fix the common case of this happening - someone locally compiling a package and not adjusting the version number. APT will _always_ consider the non-local varient to be newer when performing upgrade calculations and it will download and install it. This is well aligned with APT's core goal - to bring your system closer to the latest release. Your case has 3 seperate versions, so the algorithm starts to become very sensistive to things like sources.list order and you run into problems with collisions in the cache directory. Basically it doesn't work very well. Cache collisions could be solved by, for instance, appending the md5sum to the filename in the cache to disambiguate them, but people would complain because the filenames become uglier than they already are.. > And above all, why if I comment out any one of the 2 source lines, would it > think that the installed package is good ? Well, I remember there is a bug here. I guess it was never fixed (Matt do you know?) Basically, when it found a CRC difference it didn't take the time to check if another version matches the new CRC or not. It is likely you have the unstable version installed and the wesnoth.org version is different, so it makes 3 versions instead of 2. This makes it very confused since it always thinks the unstable version is newer than the installed version even though they are identical. When you remove unstable, it works OK because it sees wesnoth.org and can tell through the .deb size check that it needs to download a new .deb, when you remove wesnoth.org it sees only 1 version. Jason
