===== Upgrade Redahat inplace =====

Leapp is a tool that allow an inplace migration Ex from 8 to 9

Prerequisite packages:
  leapp
  leapp-upgrade-el8toel9
  pciutils
  systemd-container
  leapp-deps
  leapp-upgrade-el8toel9-deps
  python3-leapp

Create a folder /tmp/packages on offline system, copy all the rpms to /tmp/packages. Install the packages.
<cli prompt='#'>
# mkdir /tmp/packages
# cd /tmp/packages
# yum localinstall *
</cli>

Then you need to download the ISO from Redhat 9 and start the precheck and then the migration
<cli prompt='#'>
# leapp preupgrade --no-rhsm --iso /path/to/RHEL9-Binary-DVD.iso
# leapp upgrade --no-rhsm --iso /path/to/RHEL9-Binary-DVD.iso
</cli>





http://wiki.centos.org/TipsAndTricks/CentOSUpgradeTool

http://liquidat.wordpress.com/2014/07/17/howto-upgrading-centos-6-to-centos-7/