* CentOS Stream 9 was made available upstream on the 03.12.2021
* CentOS Stream 9 was made available at CERN on the 09.02.2022 and is currently a supported operating system, until the end of life of the upstream product which will be ~31.12.2026
## How does CERN use CentOS Stream 9?
### System updates
CentOS Stream 9 updates are staged
* A 'production' [repository](http://linuxsoft.cern.ch/cern/centos/s9/) is provided, which most systems will use and is updated once per week (except for critical security vulnerability patches)
* A 'testing' [repository](http://linuxsoft.cern.ch/cern/centos/s9-testing/) is also provided which is updated daily
* Snapshots of CentOS repositories are performed daily and can be found at [this URL](http://linuxsoft.cern.ch/cern/centos/s9-snapshots/)
* The 'cern-yum-tool' is a new package that can be used to easily switch between 'production', 'testing' or 'snapshot' repositories
* The 'yum-autoupdate' package is provided for automatic (distro-sync) updates (the same as CC7).
### Modified packages
* centos-stream-release:
* Yum repositories files changed to use <http://linuxsoft.cern.ch/cern/centos/s9/>
* centos-gpg-keys:
* Added CERN Koji RPM signing keys
* epel-release:
* Yum repositories files changed to use <http://linuxsoft.cern.ch/>
**Note**: Unless otherwise stated above, CentOS Stream 9 packages (rpms) are the very same packages released by the upstream CentOS team.
## Deployment / Howto
Documentation is in the process of being updated. Currently there are not too many major differences between CentOS Stream 9 and CentOS Stream 8, thus the documentation for [CentOS Stream 8](/centos8/docs) may be helpful.