A brief history of CentOS Stream, where things are going in the future, and how this will impact you as a consumer or contributor.

1. CentOS Stream
How will this impact you?

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CentOS History
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CentOS Linux ("CentOS") historically is a rebuild of Red Hat Enterprise Linux ("RHEL")
shortly after a release of an official RHEL version
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RHEL in the other hand, is derived from Fedora Linux ("Fedora") by taking a snapshot
of Fedora every 3-4 years.
●
CentOS have been very popular among users who want RHEL level enterprise quality
Linux, but unwilling, or does not require the commercial support subscription
provided by RHEL, due to:
●
CentOS , being a completely equivalent RHEL rebuild, does not add any additional
value on top of RHEL, and merely a free (as in price), alternative to RHEL.

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What It Means To Be "Stable"
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A Linux distribution ("Distro") is not a single software, but a
bundle of hundreds of software that works together to
function as a single operating system.
●
Traditionally, a Distro will be released with specific major
release of bundled software and libraries (or "Components"),
of which, during the lifetime of the release, the bundled
software and libraries will be updated in a manner not to
break the functionality of the whole distro.
– This means, an update will usually be limited to minor version of Components,
and update to a new major release is avoided unless necessary, until the new
major release of Components have been used and tested by users and
community thoroughly.
●
A "Stable" Distro means , the Distro avoids picking up new
major release, and very careful in updating to new
component versions, including minor versions, as such not
to introduce unexpected breakage.

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The Problem Of Traditional Stability
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Moves very slowly
– While very stable, it is detrimental for innovation
– Older version of Components may be lacking of features required
for specific purposes
– Bug and security fixes have to be extracted and carried backward
from new Component version to older version ("backporting")
– New applications requires newer set of Components and unable to
be installed in the Distro.
●
Installing new applications in older distro release,
and installing old application versions in new
distro release creates a set of complication.
– Applications have to require regular maintenance and
enhancement to regularly play catch up with newer version of
components, in order to support OS upgrades, which can be costly.

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Traditional Distro Release

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Fedora Modularity:
A New Approach Of Distro Packaging
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Circa 2013, Fedora Project introduced the
"Modularity Initiative"
– An approach to make a Distro able to carry multiple
"stream" of component versions.
– Streams would provide a form of stability to
applications that depends on specific major version of
components
●
Streams would regularly receive minor updates of major
versions, allowing apps to regularly receive fixes on
components, without high cost of moving to new major
version
●
OS can be regularly updated, without
risking applications to break due to
major version change.
Base OS
Module
Stream
Module
Stream
Module
Stream
Module
Stream

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Fedora Modularity

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AppStreams
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Fedora Modularity was adopted by Red Hat in RHEL8 as "Application
Streams" to offer ability for application to depend on specific major
versions of components, while still allowing OS to receive regular updates.
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However, the due the very fast pace of Fedora updating their components,
while RHEL heavy focus on stability, AppStream modules in RHEL lack
community participation.
– Those who contribute in Fedora Modularity, would only likely to see AppStream to pick up the
module years in the future
– This limits the impact of AppStream and made it less useful, as ecosystem application developers
may need the component versions sooner rather than later.
– Contributing AppStream in CentOS is very difficult, as CentOS tracks RHEL rather than RHEL tracks
CentOS. A submission to CentOS AppStream would have to go through RHEL rather than the other
way around.

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CentOS Stream
The Community Enterprise Linux
●
Traditional RHEL development flow have been behind
closed doors of Red Hat.
●
CentOS project, due to its original goal of being merely a
rebuild of RHEL, have very limited community contribution
flow.
– Bug and fixes identified by community have to be accepted by RHEL first,
before it lands on CentOS.
●
The change of focus to CentOS Stream includes a goal to
make a clearer community contribution to CentOS.

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Previous Community Contribution Flow
Stabilization & QC
Community
Contributions
Community
Contributions
Latest &
Greatest
Software
Community
Fixes &
AppStream
Rebuild

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Upcoming Community Contribution Flow
Stabilization
Community
Contributions
Community
Contributions
Latest &
Greatest
Software
Community
Fixes &
AppStream
Merge
ELN
(Enterprise Linux Next)
Stable
Enterprise Linux
Test &
QC

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To A Consumer, What Really Changed?
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What Changed:
– AppStream provides more stable ecosystem for application deployment,
allowing locking a CentOS install to specific major version of components.
– Earlier access to community contributed bugfixes
– Less barrier of entry in participating in CentOS as contributor.
– AppStream module development cycle will be more open, allowing a richer
ecosystem of modules for different purposes to be contributed by the
community
●
What Remain The Same:
– CentOS continue to be a stable OS for enterprise Linux use-cases

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Looking For Commercial CentOS Support?
●
ABYRES is a Malaysian Open Source Solution Provider
which have been providing FOSS related consulting and
professional services since 1997.
●
Our team consist of experienced FOSS consultants, and
also FOSS contributors who contributes to projects such as
Fedora, oVirt, OKD, morepath, and others.
●
Contact us at salesteam@abyres.net for information on
how we can help you in leveraging CentOS Stream and
other FOSS technologies in your enterprise.

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Refs:
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Future Is CentOS Stream:
https://blog.centos.org/2020/12/future-is-centos-stream/
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Fedora Modularity: https://docs.fedoraproject.org/en-US/modularity/
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Fedora ELN: https://docs.fedoraproject.org/en-US/eln/
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Intro to AppStream:
https://www.redhat.com/en/blog/introduction-appstreams-and-mod
ules-red-hat-enterprise-linux
●
CentOS Stream Continuous Delivery:
https://blog.centos.org/2020/12/centos-stream-is-continuous-delivery/