модульность в DNF (Modularity in DNF)
Имя (Name)
dnf.modularity - Modularity in DNF
Modularity is new way of building, organizing and delivering
packages. For more details see:
https://docs.pagure.org/modularity/
Определения (Definitions)
modulemd
Every repository can contain modules metadata with
modulemd documents. These documents hold metadata about
modules such as Name, Stream or list of packages.
(non-modular) package
Package that doesn't belong to a module.
modular package
Package that belongs to a module. It is listed in modulemd
under the artifacts section. Modular packages can be also
identified by having %{modularitylabel} RPM header set.
(module) stream
Stream is a collection of packages, a virtual repository.
It is identified with Name and Stream from modulemd
separated with colon, for example 'postgresql:9.6'.
Module streams can be active or inactive. active means the
RPM packages from this stream are included in the set of
available packages. Packages from inactive streams are
filtered out. Streams are active either if marked as
default or if they are explicitly enabled by a user
action. Streams that satisfy dependencies of default or
enabled streams are also considered active. Only one
stream of a particular module can be active at a given
point in time.
Фильтрация пакетов (Package filtering)
Without modules, packages with the highest version are used by
default.
Module streams can distribute packages with lower versions than
available in the repositories available to the operating system.
To make such packages available for installs and upgrades, the
non-modular packages are filtered out when their name or provide
matches against a modular package name from any enabled, default,
or dependent stream. Modular source packages will not cause
non-modular binary packages to be filtered out.
HOTFIX REPOSITORIES
In special cases, a user wants to cherry-pick individual packages
provided outside module streams and make them available on along
with packages from the active streams. Under normal
circumstances, such packages are filtered out or rejected from
getting on the system by Fail-safe mechanisms. To make the
system use packages from a repository regardless of their
modularity, specify module_hotfixes=true in the .repo file. This
protects the repository from package filtering.
Please note the hotfix packages do not override module packages,
they only become part of available package set. It's the package
Epoch, Version and Release what determines if the package is the
latest.
FAIL-SAFE MECHANISMS
Repositories with module metadata are unavailable
When a repository with module metadata is unavailable, package
filtering must keep working. Non-modular RPMs must remain
unavailable and must never get on the system.
This happens when:
• user disables a repository via --disablerepo or uses --repoid
• user removes a .repo file from disk
• repository is not available and has skip_if_unavailable=true
DNF keeps copies of the latest modulemd for every active stream
and uses them if there's no modulemd available for the stream.
This keeps package filtering working correctly.
The copies are made any time a transaction is resolved and
started. That includes RPM transactions as well as any dnf
module <enable|disable|reset> operations.
When the fail-safe data is used, dnf show such modules as part of
@modulefailsafe repository.
Orphaned modular packages
All packages that are built as a part of a module have
%{modularitylabel} RPM header set. If such package becomes part
of RPM transaction and cannot be associated with any available
modulemd, DNF prevents from getting it on the system (package is
available, but cannot be installed, upgraded, etc.). Packages
from Hotfix repositories or Commandline repository are not
affected by Fail-safe mechanisms.
