Priority mismatches¶
Priority mismatches are handled by the Archive Admin team.
Package priorities are defined in the debian policy, but Ubuntu does not follow these exactly. We had seeds and germinate from very early on in Ubuntu’s history and priorities mattered to various installation tools to varying extents.
When answering the question “how should we set priorities in Ubuntu?”, generating them from seeds seemed like a natural fit. We ended up with the required, minimal, and standard seeds mapping to Priority: required, Priority: important, and Priority: standard respectively, while everything else is Priority: optional (or the deprecated Priority: extra).
Priority mismatches are generally less important than component mismatches
because wrong priorities have relatively little impact. They affect the behavior
of debootstrap, but these days debootstrap resolves dependencies on its own
– so packages with a too-high priority will be pulled into default installs,
but too-low priorities don’t really impact users.
Priority mismatch report¶
The priority-mismatches file (
txt or
html)
tracks and reports priority mismatches in the Archive.
When we resolve priority mismatches¶
Regular: While processing requests and queues, an Archive Admin can handle them at any time. However, it is of relatively low priority compared to other efforts.
Towards Feature Freeze: At this time, we review priority mismatches and try to drive the list to zero. Doing so during this period still allows developers time to drop dependencies that aren’t wanted.
How to solve a priority mismatch¶
Packages shown as needing their priority raised, have this because they’ve been added as Recommends or Depends to existing central packages. We need to make sure these additions are actually desired in Ubuntu to avoid bloating the base system – sometimes they only make sense in Debian.
As with component-overrides, these are managed with change-override. To act on priority mismatches we:
Track it down to the dependency/seed change that caused it
See why it changed:
If it is OK, act and override the priority
If it is not OK, contact the package owner or the uploader of the change
Example:
$ ./change-override -n -s questing -e 3.5.0-2ubuntu1 -p required openssl-provider-legacy
The overrides for a given binary name are the same for all architectures, so attention should be given to per-arch priority-mismatches and decisions made that make sense (e.g. don’t raise the priority of powerpc-specific libraries). Due to that we should not expect the priority-mismatch report to be fully zeroed on ALL arches.