Migrating from CentOS 8 to CentOS 8 Stream

Introduction

CentOS has, until recently, been a downstream rebuild of Red Hat Enterprise Linux. Being binary compatible with RHEL made it very useful for anyone who wanted to develop applications for RHEL for free. But using CentOS for development of RHEL applications meant that development had to wait weeks or sometimes months for the most recent RHEL release to be downloaded, built and rebranded as CentOS, and then distributed before applications could be updated and tested.

Back in 2014, CentOS was purchased by Red Hat. In fact, since CentOS is an open-source project, it was really that Red Hat bought the trademark for CentOS and hired many of the people who were working on it, effectively taking ownership of the entire project. Then, in September 2019, Red Hat announced that it was creating a new CentOS version, called CentOS Stream, and inserting it into the development pipeline between Fedora and RHEL. Admittedly, this was a bit confusing.

However, this month – December 2020 – it became clear what the objective was creating the new CentOS Stream project when it announced that Red Hat would be terminating its financial support of downstream CentOS 8. This is a decision that was hailed by some and angered others.

What Really Happened?

Most of the confusion about the recent announcement pertaining to CentOS 8 comes from the reuse of the CentOS name. CentOS 8 Stream really is different from CentOS 8 because the former is upstream compared to RHEL and the latter is downstream. This basically means that new bug fixes and features are released in CentOS before they get to RHEL instead of after.

The team who had been working on CentOS 8 never really had an option to send patches, fixes, and features into the RHEL pipeline. Prior to CentOS 8 Stream, the only way to give input to RHEL was to work on RHEL directly as a Red Hat employee, or to contribute to Fedora, whose changes would only be released into the next RHEL major version (e.g. RHEL 9). But now that CentOS 8 Stream is directly upstream from RHEL, contributors can have an impact on the next minor release of RHEL, allowing their feedback to guide the current RHEL major version. This is a great benefit for developers working on OS-level applications and libraries.

Furthermore, CentOS 8 Stream is a better development platform for those wanting to run their applications on RHEL 8. Development for the next RHEL minor release can now be done in advance of the RHEL release instead of having to wait for weeks or months after the release for CentOS 8 to be built and distributed.

It really is a win-win for developers.

But, as I said, many people are angry. As far as I can tell, the people who are most upset about the recent announcement to abandon CentOS 8 at the end of 2021 are those people who were using CentOS 8 for production. Some small businesses and academics rely on CentOS 8 for their applications. But since bug releases and security fixes were always delayed getting into CentOS 8, those who are using CentOS 8 for their production systems are exposing themselves to a great deal of risk – even before commenting on the lack of support SLAs for CentOS 8.

Let’s Upgrade Already!

You probably didn’t come here to hear about the changes in CentOS 8 Stream. You came here because the article title said that you can upgrade/migrate from CentOS 8 to CentOS 8 Stream. So let’s do that!

Start with your existing CentOS 8 server. In this example, I am using a freshly-installed CentOS 8 virtual machine.

[root@centos8 ~]# cat /etc/os-release
 NAME="CentOS Linux"
 VERSION="8 (Core)"
 ID="centos"
 ID_LIKE="rhel fedora"
 VERSION_ID="8"
 PLATFORM_ID="platform:el8"
 PRETTY_NAME="CentOS Linux 8 (Core)"
 ANSI_COLOR="0;31"
 CPE_NAME="cpe:/o:centos:centos:8"
 HOME_URL="https://www.centos.org/"
 BUG_REPORT_URL="https://bugs.centos.org/"
 CENTOS_MANTISBT_PROJECT="CentOS-8"
 CENTOS_MANTISBT_PROJECT_VERSION="8"
 REDHAT_SUPPORT_PRODUCT="centos"
 REDHAT_SUPPORT_PRODUCT_VERSION="8"

Although it’s probably not strictly necessary, it’s always a good idea to make sure your system is up-to-date before trying any sort of migration.

[root@centos8 ~]# dnf update
 Last metadata expiration check: 0:18:51 ago on Wed 30 Dec 2020 06:12:24 PM UTC.
 Dependencies resolved.
=======================================================================================
  Package                 Arch               Version               Repository      Size
=======================================================================================
 Installing:
  centos-linux-release    noarch             8.3-1.2011.el8 BaseOS                 22 k
      replacing centos-release.x86_64 8.2-2.2004.0.1.el8
      replacing centos-repos.x86_64 8.2-2.2004.0.1.el8
  kernel                  x86_64             4.18.0-240.1.1.el8_3  BaseOS          4.3 M
  kernel-core             x86_64             4.18.0-240.1.1.el8_3  BaseOS          30 M
  kernel-modules          x86_64             4.18.0-240.1.1.el8_3  BaseOS          26 M
 Upgrading:
  NetworkManager          x86_64             1:1.26.0-9.el8_3      BaseOS          2.4 M
  NetworkManager-libnm    x86_64             1:1.26.0-9.el8_3      BaseOS          1.7 M
 [CLIP]

Once your CentOS 8 system is up-to-date, reboot before the next step.

[root@centos8 ~]# reboot

Now we need to install the CentOS 8 Stream release repositories.

[root@centos8 ~]# dnf install centos-release-stream
 Last metadata expiration check: 0:00:55 ago on Wed 30 Dec 2020 06:47:45 PM UTC.
 Dependencies resolved.
=======================================================================================
  Package                     Architecture Version                  Repository    Size
=======================================================================================
 Installing:
  centos-release-stream       x86_64       8.1-1.1911.0.7.el8       extras        11 k
 Transaction Summary
 Install  1 Package
 Total download size: 11 k
 Installed size: 6.6 k
 Is this ok [y/N]: y
 Downloading Packages:
 centos-release-stream-8.1-1.1911.0.7.el8.x86_64.rpm    24 kB/s |  11 kB     00:00    
---------------------------------------------------------------------------------------
 Total                                                  15 kB/s |  11 kB     00:00     
 Running transaction check
 Transaction check succeeded.
 Running transaction test
 Transaction test succeeded.
 Running transaction
   Preparing        :                                                              1/1 
   Installing       : centos-release-stream-8.1-1.1911.0.7.el8.x86_64              1/1 
   Verifying        : centos-release-stream-8.1-1.1911.0.7.el8.x86_64              1/1 
 Installed:
   centos-release-stream-8.1-1.1911.0.7.el8.x86_64                                     
 Complete!

Some articles online will tell you that all you have to do now is update, but actually that won’t suffice. That will only serve to update any packages that might be older. It will not actually make your system match what’s in the CentOS 8 Stream repositories. For that, we need the distro-sync command.

[root@centos8 ~]# dnf distro-sync
 CentOS-Stream - AppStream                             4.5 MB/s | 6.4 MB     00:01    
 CentOS-Stream - Base                                  1.3 MB/s | 2.4 MB     00:01    
 CentOS-Stream - Extras                                4.5 kB/s | 7.0 kB     00:01    
 Dependencies resolved.
=======================================================================================
  Package                     Arch   Version                    Repository        Size
=======================================================================================
 Installing:
  centos-stream-release       noarch 8.4-1.el8                  Stream-BaseOS     21 k
      replacing  centos-linux-release.noarch 8.3-1.2011.el8
      replacing  centos-release-stream.x86_64 8.1-1.1911.0.7.el8
  kernel                      x86_64 4.18.0-259.el8             Stream-BaseOS    5.0 M
  kernel-core                 x86_64 4.18.0-259.el8             Stream-BaseOS     31 M
  kernel-modules              x86_64 4.18.0-259.el8             Stream-BaseOS     27 M
 Upgrading:
  NetworkManager              x86_64 1:1.30.0-0.4.el8           Stream-BaseOS    2.5 M
  NetworkManager-libnm        x86_64 1:1.30.0-0.4.el8           Stream-BaseOS    1.8 M
[CLIP]

Once that process is done, you will see that the OS-release is now CentOS 8 Stream.

[root@centos8 ~]# cat /etc/os-release 
 NAME="CentOS Stream"
 VERSION="8"
 ID="centos"
 ID_LIKE="rhel fedora"
 VERSION_ID="8"
 PLATFORM_ID="platform:el8"
 PRETTY_NAME="CentOS Stream 8"
 ANSI_COLOR="0;31"
 CPE_NAME="cpe:/o:centos:centos:8"
 HOME_URL="https://centos.org/"
 BUG_REPORT_URL="https://bugzilla.redhat.com/"
 REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux 8"
 REDHAT_SUPPORT_PRODUCT_VERSION="CentOS Stream"

And don’t forget to reboot!

[root@centos8 ~]# reboot

Conclusion

For anyone who is developing applications to run on Red Hat Enterprise Linux 8, CentOS 8 Stream really is a blessing since you now have access to a stable operating system on which your application will eventually run. Also, if your development process uncovers any OS bugs, then your fixes and suggestions will find their way into the next minor release of RHEL and won’t have to wait for the next major release.