On CentOS Stream systems the `stream` DNF variable is used instead of the `releasever`. It needs to be handled correctly during the upgrade - and the persistent definition of the variable should be updated after the system is upgraded.

Snippet from the /etc/yum.repos.d/centos.repo file:

[baseos]
name=CentOS Stream $releasever - BaseOS
metalink=https://mirrors.centos.org/metalink?repo=centos-baseos-$stream&arch=$basearch&protocol=https,http
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-centosofficial
gpgcheck=1
repo_gpgcheck=0
metadata_expire=6h
countme=1
enabled=1

The variable:

# cat /etc/dnf/vars/stream
9-stream

Additional info:

• DNF variables defined in varfiles is not possible to override using DNF4. We have to either override the file (we can inside overlayfs scratch container) or we need to define our own `varsdir`.