Changes/SwitchToDnf5

Switch to dnf5

This is a proposed Change for Fedora Linux.
This document represents a proposed Change. As part of the Changes process, proposals are publicly announced in order to receive community feedback. This proposal will only be implemented if approved by the Fedora Engineering Steering Committee.

Summary

Change the default package manager from dnf to dnf5.

Owner

• Name: Jan Kolarik
• Email: jkolarik@redhat.com

• Name: Jaroslav Mracek
• Email: jmracek@redhat.com

Current status

• Targeted release: Fedora Linux 41
• Last updated: 2024-03-28
• Announced
• Discussion Thread
• FESCo issue: <will be assigned by the Wrangler>
• Tracker bug: <will be assigned by the Wrangler>
• Release notes tracker: <will be assigned by the Wrangler>

Detailed Description

This proposal will implement several topics, which are outlined below.

Provider of the dnf command

This change proposes to switch the current provider of the /usr/bin/dnf symlink from dnf to dnf5. Currently, the symlink target is /usr/bin/dnf-3, provided by the dnf sub-package, python3-dnf. Upon implementation of this change, the symlink will point to /usr/bin/dnf5, provided by the dnf5 package.

Prepare the upgrade path

The dnf5 package, serving as the new provider of the /usr/bin/dnf symlink, will obsolete the dnf package starting with Fedora 41. Upon the release of this dnf5 package, upgrading the system or installing dnf5 will replace the existing dnf package on the system. Additionally, the dnf5 package will provide a /usr/bin/yum symlink for backwards compatibility and the dnf-automatic command will be obsoleted.

Feature parity with dnf

We aim to cover the majority of use cases available in the existing dnf package. However, there are some features that may not be implemented in time. Nevertheless, we plan to deliver them at a later stage.

Plugins

The progress of implementing plugins to match the current set from the dnf-plugins-core package is tracked upstream. Among the missing plugins, we still plan to implement:

• debuginfo-install plugin
• reposync plugin

Modularity

As support for modularity was retired in Fedora 39, dnf5 currently only implements a basic feature set for listing and enabling/disabling modules.

Background service support

A new daemonized service, dnf5daemon, utilizing the D-Bus interface, is prepared for clients as a sub-package. This will serve as an alternative or replacement for the PackageKit layer. Integration of dnf5daemon support into the default Fedora user interface, GNOME Software, is currently in progress

Documentation of API changes

The public interface has undergone significant changes to enhance the user experience and remove unused and obsolete code components. To facilitate user migration to the new CLI and API interfaces, a guide was prepared covering all differences compared to the interface provided by the existing dnf package, along with examples of typical use cases.

Deployment tasks

During the deployment of the dnf5 package manager as the new default, several adjustments need to be made both to the infrastructure and the dnf5 package itself. Some of these adjustments are detailed below. To ensure synchronization and address all necessary changes, we've established an upstream tracking issue.

Feedback

As this is the second iteration of such a proposal, we've gathered a lot of feedback from various sources during the first attempt to accept this change.

FESCo inputs

A ticket discussing the reasons why the contingency mechanism was invoked for the first attempt of the proposal was opened by FESCo. It includes a list of items that are either incomplete or in progress.

Below is a list of issues from the ticket that are still unresolved or require clarification on their current status. Other items not mentioned below are considered completed.

Switch in ELN

This should not block the proposal, as the current plan is to target RHEL 11. Integration can occur there after the proposal is implemented for Fedora 41.

Aligning configuration with the current state in dnf

All overrides to match the current state of dnf configuration will be provided to the Fedora release project, see below.

System upgrade and offline transactions

The implementation work has been completed and is already present upstream. We anticipate extensive testing during the summer, and we also plan to organize testing days for this purpose.

Dropping the Snapper plugin

In dnf5, we've adopted a new approach for implementing functionality that was previously handled by the Snapper plugin in dnf.

We're introducing the Actions plugin, which offers more capabilities than the Snapper plugin, including support for running external applications before or after transactions and interacting with the dnf5 configuration. Here is the documentation for the Actions plugin, which includes examples of how to emulate the behavior of the Snapper plugin.

Messages from RPM scriptlets

An issue with output from RPM scriptlets is the potential length, coupled with the absence of a standardized policy for distinguishing between important and unimportant messages.

Currently, all messages are logged in the dnf5 log files, with differentiation based on their originating scriptlets, representing an improvement over dnf. Additionally, in case of transaction errors, the scriptlet output is included in the standard output. Furthermore, there is already a resolved ticket in the infrastructure to incorporate logs on the builders.

Testing days

We've already held several dnf5 test days for Fedora 38, 39, and recently also 40. We've made efforts to document all reported issues in our upstream tracking system, and major issues should now be resolved. Some of these issues were related to user documentation, improving command-line outputs, and enhancing overall user experience. These topics are next on our priority list after completing the functionality for mandatory commands and plugins.

Fedora QA scenarios

We've started a discussion thread on the requirements for accepting this proposal from a QA perspective. A list of relevant test cases and criteria has been mentioned, which we'll review to ensure we've covered everything on our end.

Fedora CI readiness

The dnf project is also deployed in the CI pipeline. We've initiated communications with this team to ensure that all dnf functionality used there is either already implemented in dnf5 or can be addressed through an alternative dnf5 method. We've already received some feedback from the first iteration of the proposal.

Tracking issue upstream

When implementing the first iteration of this proposal, we created an upstream ticket to track all bugs or lack of needed functionality. All items have been addressed, and only several known deployment issues remain, which need to be managed at the time of the next switch.

Benefit to Fedora

The new dnf5 will significantly improve the user experience and performance. Detailed descriptions of individual areas are provided below.

Reduced footprint

The dnf5 package is a fully-featured package manager that doesn't require Python dependencies.

It also reduces the number of software management tools in Fedora by replacing both the dnf and microdnf packages.

The installation size of the dnf5 stack in an empty container is approximately 60% smaller than the dnf installation.

Currently, dnf, microdnf, and PackageKit use their own cache, leading to significant metadata redundancy. With dnf5 and dnf5daemon, which share metadata, this redundancy will be eliminated.

Enhanced performance

Loading and downloading repository metadata now occur concurrently.

Package query operations, including processing numerous command-line arguments, have been significantly accelerated.

Lowered maintenance costs

Many functional duplicates in dnf were eliminated during the development of the new dnf5 package manager. This was partly because the integration of the original PackageKit and dnf libraries into the original libdnf library was never completed.

Plugins are now included in the same package as the core functionality.

Unified user experience

Consistent user experience is offered to users across servers, workstations, and containers, as dnf5 is the sole package manager deployed there. Existing dnf, yum, and microdnf commands will be linked to dnf5, while compatibility aliases for essential use cases will be provided to facilitate migration.

Configuration files will be shared among dnf5 components.

API users will encounter unified code style and naming conventions. Various scripting language interfaces are now provided from a single source using SWIG bindings (formerly CPython and SWIG).

Scope

Proposal owners

The remaining work on the proposal can be divided into several sections.

Feature implementation

System upgrade

This command is essential for upgrading the system to the next release. While the implementation is already completed, we plan to conduct extensive testing, including community participation, to minimize the risk of issues occurring in production.

History command

The functionality related to manipulating transaction history has not yet been implemented. However, following the completion of the system upgrade functionality, it is currently our top priority. Due to the significant overlap between the functionality in the history command and the system upgrade functionality, we anticipate its readiness shortly thereafter.

GNOME Software support

The integration of dnf5 support, particularly dnf5daemon, into GNOME Software is currently underway. Developers from both DNF5 and GNOME Software are closely connected and regularly synchronize the progress of their work.

Documentation

While our current priority is achieving full coverage of user and API documentation, there may still be some undocumented parts of the code. Please don't hesitate to report any such issues upstream, and we'll endeavor to address them promptly.

Early access for developmental branch users

The intention is to implement the proposed changes in the Rawhide developmental branch prior to the date specified in the Contingency Deadline section, targeting the transition period between March and April. It is anticipated that certain mandatory items for the regular release, as outlined in previous sections, may not be completed by this time.

System upgrade

This functionality is unnecessary as Rawhide operates on a rolling release model.

GNOME Software

Rawhide users will continue to utilize the current PackageKit backend connected to the existing libdnf interface until the integration of dnf5 is finalized. These libraries can coexist with the new dnf5 package on the same system. For more details, see below.

Other developers

The following components are already prepared for transition to dnf5:

• Ansible
• Lorax
• Mock

Below is a list of dependencies that have not yet integrated with dnf5.

Anaconda

Migration to the dnf5 API will not be implemented at this time. After discussion with the Anaconda team, it was determined that there isn't sufficient capacity and time to complete the work on schedule. Therefore, the existing dnf4 Python bindings from the python3-dnf package will continue to be used for now.

GNOME Software

This integration is already addressed in the section above, as it involves collaborative efforts.

Release engineering

Building with dnf5

The Fedora infrastructure has been utilizing dnf5 for building Fedora 40+ chroots since before the Fedora 40 mass rebuilds began. This implementation was based on the system-wide change outlined here.

Apply downstream configuration overrides

Starting with dnf5, distro-specific overrides of the default configuration values are implemented using drop-in directories. Options with different values upstream compared to the current state of dnf in Fedora will be filed in a pull request against the Fedora release project.

Update of kickstarts for image composes

The dnf team will prepare a pull request to include the packages for the new default dnf5 package manager in the Fedora Kickstarts project.

Update of package groups definitions

The dnf team will prepare a pull request to include the packages for the new default dnf5 package manager in the Fedora Comps project.

Update of KIWI image descriptions

The dnf team will prepare a pull request to include the packages for the new default dnf5 package manager in the Fedora KIWI descriptions project.

Upgrade/compatibility impact

Running the upgrade

The dnf5 package will be installed on the system to provide /usr/bin/dnf, replacing the existing dnf package as it becomes obsolete. Additionally, the dnf automatic tool will be replaced by the new dnf5 automatic plugin.

Below is an example of performing this upgrade transaction.

$ sudo dnf upgrade
Last metadata expiration check: 0:01:09 ago on Wed 13 Mar 2024 05:48:25 AM EDT.
Dependencies resolved.
================================================================================
 Package                	Arch    	Version         	Repository 	Size
================================================================================
Installing:
 dnf5-plugin-automatic  	x86_64  	5.1.14-1.fc41   	rawhide  	120 k
 	replacing  dnf-automatic.noarch 4.19.0-1.fc40
Upgrading:
 dnf-data               	noarch  	4.19.0-1.fc41   	rawhide   	40 k
 python3-dnf            	noarch  	4.19.0-1.fc41   	rawhide  	551 k
Installing group/module packages:
 dnf5                   	x86_64  	5.1.14-1.fc41   	rawhide  	599 k
 	replacing  dnf.noarch 4.19.0-1.fc40
 	replacing  yum.noarch 4.19.0-1.fc40
Installing dependencies:
 fmt                    	x86_64  	10.2.1-3.fc40   	rawhide   	125 k
 libdnf5                	x86_64  	5.1.14-1.fc41   	rawhide  	991 k
 libdnf5-cli            	x86_64  	5.1.14-1.fc41   	rawhide   	229 k
Installing weak dependencies:
 bash-completion        	noarch  	1:2.11-15.fc41  	rawhide   	360 k

Transaction Summary
================================================================================
Install  6 Packages
Upgrade  2 Packages

Binaries and symlinks

The existing dnf binaries will remain on the system and will be available at /usr/bin/dnf-3, which refers to the Python 3 version to which dnf was migrated in the past. Additionally, they will be accessible at /usr/bin/dnf4, which is a symlink to the dnf-3 script and denotes the major version of the dnf binary. This binary naming convention is also used for /usr/bin/dnf5, which will become the target of the /usr/bin/dnf symlink.

Below is the output of the tree command showing the expected file structure after the upgrade.

Before upgrade

$ tree /usr/bin/ -P dnf*
/usr/bin/
├── dnf -> dnf-3
├── dnf-3
└── dnf4 -> dnf-3

After upgrade

$ tree /usr/bin/ -P dnf*
/usr/bin/
├── dnf -> dnf5
├── dnf-3
├── dnf4 -> dnf-3
└── dnf5

Different system state

Though the RPM DB, which contains the database of installed packages, remains the singular source in the system, the transactional history and installed packages reasons in dnf and dnf5 is not shared, and they now use different formats.

Transactions performed in dnf will not be visible in dnf5, and vice versa. Therefore, when concurrently using dnf and dnf5 on the system, packages installed by one of them as dependencies will appear as user-installed to the other one, potentially leading to them not being auto-removed later.

While the history database is not migrated to dnf5, when running a transaction in dnf5 for the first time, an attempt is made to convert and load the existing system state from dnf. This should preserve information about the reasons for installed packages and prevent them from being treated as user-installed, requiring manual removal from the system instead of being seen as dependencies of explicitly removed packages.

Compatibility

While the majority of CLI use cases for managing packages should remain the same, the dnf5 API has undergone significant changes. To ease adoption, dnf5 will provide compatibility aliases for commands and options. Additionally, user output will differ, and we plan to offer machine-readable support for most commands. For more details, please refer to the section above.

Applications encountering difficulties with dnf5 adoption can continue using the existing dnf CLI and API provided by the python3-dnf and libdnf packages. These libraries can be used in parallel on the system, but modifying installed software is not recommended due to differences in system state, as mentioned in the previous section.

How To Test

Copr repository

A testing Copr repository has been set up with dnf5 already deployed as the default package manager. Instructions on how to proceed are provided alongside.

Quay containers

We have also prepared Fedora container images with the dnf5 stack preinstalled on quay.io, making it easy to test in isolation with Podman.

Side-tag for testing

Before pushing the new dnf5 into the Rawhide compose, we plan to announce the prepared side-tag containing this new package publicly. This will allow interested parties to test it against their software.

Testing days

We are planning at least two iterations of testing days before dnf5 is delivered into Fedora 41. One will focus on testing the overall functionality of dnf5, with an emphasis on parts that were not tested during previous testing days. The other iteration will center around testing the system upgrade functionality.

Communication channels

Community feedback, including bug reports, issues, or feature requests, is highly encouraged.

Our primary communication channel is upstream, where you can report issues, participate in discussions, or even propose pull requests. We are happy to review them.

Issues specific to a particular version of the dnf5 package can also be reported through the Bugzilla tracking system, which we also monitor.

User Experience

Faster query processing

The processing of package metadata is now significantly faster. Executing commands such as repoquery to list packages available in repositories is now twice as fast compared to dnf. Similarly, operations like listing dependencies or parsing numerous command-line arguments are notably expedited, potentially saving users seconds to tens of seconds in waiting time for the results.

Consolidated and streamlined API

The API for managing packages, working with repositories, and solving package dependencies is now consolidated into a single component, providing a unified solution. The original dnf API underwent a review process, during which unused workflows and obsolete methods were removed, while improving usability for users.

Enhanced command-line outputs

Transaction tables now offer more detailed information, verbose scriptlet outputs are redirected and organized by package name into log files, individual commands come with their own man pages, bash completion has been enhanced, and numerous other improvements have been made.

Dependencies

Owned by our team

dnf-plugins-core

Installed plugins will persist on the system and remain functional using the dnf4 binary from the python3-dnf package.

With the exception of the system upgrade plugin, all essential plugins are now implemented in dnf5 and are provided by the dnf5-plugins package or dnf5 directly.

dnf-plugins-extras

Installed plugins will persist on the system and remain functional using the dnf4 binary from the python3-dnf package.

Porting the functionality to dnf5 is currently of low priority, and its implementation depends more on community involvement. The functionality of the Snapper plugin is already covered by the dnf5 actions plugin.

Requirements on dnf

This is the most critical category of packages as issues connected with them can potentially disrupt the system upgrade path.

Here, we can split components into two groups.

The first group utilizes dnf from the command line interface (CLI), and thus, they either need to adjust to the new syntax and behavior of dnf5 or switch to utilizing the existing dnf4 binary directly.

The second group consists of components providing plugins for the dnf command. These plugins will remain functional using the binary from python3-dnf, requiring packaging changes to depend on this package instead.

auter
calamares
copr-builder
cpanspec
dnfdragora
etckeeper-dnf
fedora-review
fedora-upgrade
kiwi-systemdeps-core
libdnf-plugin-subscription-manager
lpf
mock
osbuild
perl-CPAN-Plugin-Sysdeps
rbm
rpmdistro-repoquery
supermin
system-config-language

A tracking issue was created in advance to inform maintainers about the planned switch to dnf5.

Requirements on python3-dnf

Here, we can also categorize components into two groups.

The first group consists of components providing plugins for the dnf command. These plugins will remain functional using the binary from python3-dnf, requiring packaging changes to depend on this package instead.

The second group utilizes the dnf’s Python API, and they should not be directly affected by the change. However, testing is still necessary, and it is strongly recommended to consider porting to the dnf5 API.

anaconda-core
copr-builder
dnf-plugin-diff
dnf-plugin-ovl
dnfdaemon
fedora-easy-karma
fedora-review
fedrq
lorax
mock-core-configs
module-build-service
modulemd-tools
needrestart
policycoreutils-devel
pungi
python3-dnf-plugin-cow
python3-dnf-plugin-flunk_dependent_remove
python3-dnf-plugin-perfmetrics
python3-imgcreate
python3-libreport
retrace-server
subscription-manager
system-config-language

Requirements on libdnf

These packages utilize the libdnf API and should not be directly impacted by the change. However, testing is still necessary.

Tools that modify system software, such as PackageKit, may exhibit different behavior when used alongside dnf5 to manage the same system, as previously described.

Additionally, it is strongly recommended to consider porting to the dnf5 API in this context.

PackageKit
copr-builder
libdnf-plugin-subscription-manager
libdnf-plugin-swidtags
libdnf-plugin-txnupd

Requirements on python3-hawkey

These components utilize unsupported Hawkey Python bindings and should not be directly impacted by the change. However, thorough testing is necessary. Again, it is strongly recommended to consider porting to the dnf5 API in this context.

mock-core-configs
modulemd-tools
python3-rpmdeplint
retrace-server

Contingency Plan

Contingency mechanism

To revert to the previous state with dnf as the default package manager on the system, the following steps would be necessary:

• Packaging changes in dnf5 to remove the obsoletion of dnf and provider of the /usr/bin/dnf symlink.
• Untagging the candidate dnf5 package from the compose.
• Components that adapted to the dnf5 CLI must synchronize in this process and revert the changes to use dnf4 again. Proactive communication will be conducted similarly to how components were informed about the dnf5 migration.

Contingency deadline

Branch Fedora Linux 41 from Rawhide

Blocks release?

No