We have been importing sets of RPMs into Conary capsule packages, and yesterday we announced why.

Capsules are simple. We wrap existing packages provided in some other format (RPM, in the first instance, but we expect others) in rich Conary metadata (file-based dependencies based on deep file inspection, groups, and so forth), and store the combination of the unmodified package and metadata in the Conary repository. To install the package on a Conary-managed system, Conary calls the native package management code.

This works amazingly well. You can even mix native Conary packages with capsules.

This capsule feature can even help find bugs in RPM packages!

As part of this work, we imported RPMs from the original Red Hat Enterprise Linux 5 ISO images into a repository and tried to build a Conary group containing those packages. Unfortunately, this group was not dependency-complete. It appears that during RHEL 5 development, several packages were built against Firefox 1.5.0.7. Then (I would suspect near the end of RHEL 5 development, though I haven't checked build dates) Firefox was updated to 1.5.0.9. Someone remembered that the yelp package would need to be rebuilt against Firefox 1.5.0.9 to function. No one, apparently, remembered that gnome-python2-extras also needed to be rebuilt against Firefox 1.5.0.9. I don't blame anyone for this; I wouldn't either. But with Conary, all we had to do was try to add all the packages to a group and Conary complained and told us exactly what was wrong. By contrast, RHEL 5 was released with gnome-python2-extras that included an RPATH entry referencing a directory that does not exist: a broken dependency. As far as RPM's more limited view of dependencies is concerned, RHEL 5 was dependency-complete, but the combination of Conary's deep file inspection and group dependency checking caught this bug immediately.