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/

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.

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.  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.)

AUTHOR

       See AUTHORS in DNF source distribution.

COPYRIGHT

       2012-2021, Red Hat, Licensed under GPLv2+