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Re: How does yum work ??



Michael Schwendt wrote:

> The interaction between Yum, package metadata and RPM should be fairly
> obvious. Yum accesses local or remote repositories, which usually are
> normal http/ftp servers that contain RPM packages plus the
> corresponding metadata archives generated by the createrepo tool. The
> metadata describe the available packages beyond the information
> available in the filenames and without the need to download full
> packages. Basically, many data from a file's RPM package header (such
> as name, epoch, version, release, arch, excludearch and exlusivearch
> lists, dependency details, package capabilities, virtual package
> names, library SONAMEs, obsoletes, conflict definitions, but also
> filelists) are copied into the metadata archives, but in a format that
> is more convenient and faster to parse, e.g. xml or sqlite files.
> Having learned what packages are available in the repositories, Yum
> queries the local RPM database to examine what packages are installed
> already. Combining the information it is able to determine what newer
> packages are available as updates which is Yum's primary purpose.
> Since updates can also replace other packages or require new packages
> to be added, there's quite some time spent on processing and resolving
> lots of package metadata. For any packages to be installed, it either
> downloads them via the network or accesses them locally. It then uses
> the RPM library to examine a transaction set of packages further in
> order to find out whether there are any dependency problems or
> conflicts before asking RPM to perform a transaction. That's only a
> very brief coverage of what Yum does.

That seems to me a very clear description -
I imagine exactly what the OP wanted.

I find yum very good.
It would be even better, I think, if it gave a little more information
about what it is doing, eg what repository it is visiting
(one only learns this if the operation fails),
what files on the computer it is writing, etc.

-- 
Timothy Murphy  
e-mail (<80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland


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