Installing Redhat upgrade tool:
redhat-upgrade-tool is not available on standard repositories, you must set up the repository to install it.
# vi /etc/yum.repos.d/upgrade.repo
Place the following entries in it.
[upgrade] name=upgrade baseurl=http://dev.centos.org/centos/6/upg/x86_64/ enabled=1 gpgcheck=0
Install the following packages.
# yum -y install preupgrade-assistant-contents redhat-upgrade-tool preupgrade-assistant
Run the following command to check the potential problem you might encounter with an upgrade from CentOS 6 to CentOS 7 before making a changes to the system.
The output of preupg command has been shorted to reduce the length of the post.
We are going to use the repo file for the upgrade, issue the following command to import the GPG key.
# rpm --import http://centos.excellmedia.net/7.0.1406/os/x86_64/RPM-GPG-KEY-CentOS-7
As per the man page, the following command is used to upgrade the CentOS 6; this will download the packages from the internet.
# redhat-upgrade-tool --network 7.0 --instrepo http://centos.excellmedia.net/7.0.1406/os/x86_64/
This may result in an error:
setting up repos... .treeinfo | 1.1 kB 00:00 preupgrade-assistant has not been run. To perform this upgrade, either run preupg or run redhat-upgrade-tool --force
So, re-run the redhat-upgrade-tool with the –force option (not recommended, but this is only solution as of now)
# redhat-upgrade-tool --network 7.0 --force --instrepo http://centos.excellmedia.net/7.0.1406/os/x86_64/
On finish, Reboot to start upgrade.
Upgrade toCentOS 7:
The server will boot with the redhat-upgrade-tool kernel to upgrade the CentOS 6, now you can find the up-gradation activity via console.
Now you can see the installation of the packages.
Once completed, you will get the login screen.
Verify using the following command.
# cat /etc/redhat-release CentOS Linux release 7.0.1406 (Core)