[Yum] header.info format?

Michael Stenner mstenner at ece.arizona.edu
Wed Sep 22 23:32:47 UTC 2004


On Wed, Sep 22, 2004 at 06:16:14PM -0500, Christopher J. Bottaro wrote:
> where can i get documentation on the header.info format?  where can i get
> more detailed information on the inner workings of yum beyond what is
> covered by http://linux.duke.edu/projects/yum/howitworks.ptml.  how does it
> know what is installed on your system vs what is available in the repos vs
> what you have but needs to be updated, etc?  the stuff stored
> in /var/cache/yum is only the package info for the repositories, right? 
> (i.e. the info in the caches tell nothing about your actual system)?  yum
> then runs rpm to query your actual system then it compares that output to
> what it has in the caches...?

 * if you are planning on working on yum stuff (whether you ever
   intend to contribute it or not), you should do new develpment on
   the cvs branch, which is available as 2.1.x.  In that, the
   header.info and header files are no longer used.  They're replaced
   by a series of xml files that contains the necessary data.

 * there is no real documentation of the inner workings of yum other
   than the source code itself.

 * the information about what's available in the repos is contained in
   header.info and header files for the old style, and in the xml
   files for the new style.  This info is on the repo and is fetched
   (what's needed and new, anyway) each time yum runs.

 * yum can tell what's on your system because rpm keeps a database
   with all that information in it.

 * yum does not run the rpm executable, but rather uses the rpm-python
   bindings which allow direct (and cleaner) access to the
   information.  This is how the rpmdb is access, how packages are
   installed, etc.

If you have one or two small followup questions, feel free to ask
them.  Otherwise, you should simply turn to the source code.  I hope
that helps.
					-Michael
-- 
  Michael D. Stenner                            mstenner at ece.arizona.edu
  ECE Department, the University of Arizona                 520-626-1619
  1230 E. Speedway Blvd., Tucson, AZ 85721-0104                 ECE 524G



More information about the Yum mailing list