Information On Upgrade From CentOS 7 to CentOS 8
You may be aware that the CentOS community has released CentOS 8 on September 24, 2019. This new release is based on Red Hat Enterprise Linux 8 and holds all features of Red Hat Enterprise Linux 8.
READ: CentOS 8 – New Features
Red Hat provided a path to upgrade from RHEL 7 to RHEL 8 for its customers who are interested in upgrading RHEL 7. Customers who are running Red Hat Enterprise Linux 7.6 can upgrade their system to Red Hat Enterprise Linux 8.
Like Red Hat, we expected the CentOS community would provide some option to upgrade from CentOS 7 to CentOS 8.
Unfortunately, the tool leapp that helps to upgrade from RHEL 7 to RHEL 8 may not be available for now, and it seems the CentOS community has no plans to support this package for CentOS as per TrevorH on the CentOS Bug Tracker.
In his words,
From: CentOS Bug Tracker.
The preupgrade tool to upgrade from CentoS 6 to CentOS 7 lacked maintainers, and it no longer works.
So, we afraid to say we may not be seeing any options to upgrade from CentOS 7 to CentOS 8 near future. As a recommendation, we ask you to do the clean installation of CentOS 8.