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Re: Some ideas/questions about yum

On Fri, 28 Aug 2009, Hedayat Vatnakhah wrote:

Hi all,
Currently, Fedora package management is one of the most annoying part of Fedora experience for new desktop users (at least for those without fast, always available internet connection). For such users, Fedora package management "Just Doesn't Work"! I've almost never been able to demonstrate using fedora package management tools for a fresh Fedora install without the need to use command line, editing yum configuration file(s), killing current running yum/package kit instance(s), installing some small rpm packages using rpm command instead of using yum or graphically, etc. And sometimes, I found it better to download yum metadata using another application and copying the downloaded file to yum cache; or even completely skip yum and use rpm and manually resolve dependencies when they are not too much!

Have you filed bugs on any of these issues or are they strictly due to unreliable network connections?

First, I've some suggestions/requests which doesn't seem to need much work, and then some ideas which I'd like to know your opinions about. 1. Since Fedora 4, Fedora doesn't support installing software from DVD "out of the box". Fedora 8 is an exception here. Currently, it seems that the work is almost done (99% completed as in [1]), and fixing the remaining 1% doesn't seem to need much work but unfortunately it seems that it is stopped. I think requesting a small collaboration between the feature owner, PolicyKit and/or GIO people is not too much.

Alsadi has done a great deal of work to make this happen and I believe it is likely it will go in for F13.

2. Maybe yum could be a bit more forgiving about inaccessible repositories when running. Consider this case: a new offline user installs Fedora, and then runs "Add/Remove Software". Currently, if he clicks on "all packages", he'll see an error message that yum is unable to contact fedora repository. I think it is better to show a warning to user about being unable to contact online repositories and then show all installed packages + the packages from all accessible repositories. IMHO it is much more reasonable than expecting the user to disable all such repositories in such cases (yum/packagekit can be a bit more intelligent and do it itslef).

Disabling repos which are unavailable/inaccessible is a pretty dangerous behavior. If you're doing a 'yum install foo' and the only 'foo' you have access to is insecure - but a secure 'foo' is in the updates dir - it would be better for you to not install 'foo' at all than install a bad one.

Now, some ideas:
3. AFAIK, currently yum's primary database file contains information about packages, and all of the files in directories such as /usr/bin and /usr/lib, so that it can resolve package and file level dependencies. Isn't it possible to move file level information outside primary db (e.g. to primary_file_deps.db) and translate internal dependencies from file level dependencies to package level dependencies when creating repositories? (So that provides and requires tables in primary db only contain package references rather than file references?). It might be even possible to do it for dependencies outside repository; for example when creating updates repository, you can introduce fedora repository to createrepo, so it can translate all of the file level dependencies of updates packages also.

Except none of this will work for dependencies for 3rd party repos at all. Nor will it adequately handle any of the cases where we have multiple pkgs which provide the same file.

4. Even if the above solution is possible and can reduce the size of primary db, it won't solve the main problem: for large repositories, you'll need to download large database files. You'll need to download extra database files on some use cases anyway. So, it can be said that currently yum doesn't scale well.

no - it can be said that yum if you have a lot of pkgs you have a lot of metadata. That's not a function of yum scaling that's a function of network connectivity.

What do you think about it: we can implement parts of yum at the server side (e.g. a web service), and do queries online. The client can submit queries to online repositories, aggregate the results (+using local repositories by itself) and do appropriate actions. It can also store received data to be used when offline or while they are valid. It'll be completely backward compatible with the current clients: those who use the old method can download repositories themselves, like what they do now. It is possible to think about further details and design it completely, but I want to know about your opinions about the whole idea.

That's what up2date and rhn did in rhl6->rhel3. There are multiple problems:

1. we need a single web service that many systems would access to query for depsolving If you want to talk about things NOT scaling....

2. it would mean anyone wanting to do a respin couldn't just setup a website or an ftp mirror or a file:/// repo - they'd have to setup a web service and populate it. That's some pretty serious overhead.

3. 3rd party repos would have to go through a whole other level of hoop jumping.

Now, I don't think anyone is opposed to seeing some of these things but given what you've said on the yum-devel mailing list (where much of this discussion should be anyway) you don't seem to be interested in actually working on it or have the time. Did that change?


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