Upgrading centos6.X to centos7

[Emma Hickam]

Hi,

I am a new user in linux and i am using centos 6.5. I tried to upgrade my machine to centos 7 it by using the command yum update but i was not able to upgrade it to centos 7. Can anyone tell me how to upgrade my machine to centos 7.....

[Vipin]

Hello Emma,

Are you trying to upgrade your Desktop OS or the VM OS?? As you may know, starting RHEL 7 Red Hat introduces support for upgrading to major releases (RHEL 6.5 –> RHEL 7) via a tool called redhat-upgrade-tool. It may possibly not work by default on production environments, so use with care.

Download required packages:

# mkdir -p /root/upgrade
# cd /root/upgrade

Download latest version of preupgrade-assistant, preupgrade-assistant-contents,preupgrade-assistant-ui and redhat-upgrade-tool using wget command. You could download these lists from the Centos repositories: http://dev.centos.org/centos/6/upg/x86_64/Packages/

Install preupgrade assistant
# yum localinstall preupgrade-assistant-*

Run preupgrade assistant
# preupg
This does a check on the installed system and tries to identify potential issues after the upgrade. It should be run until all tests pass successfully.

Install redhat-upgrade-tool
# yum localinstall redhat-upgrade-tool-x.x.x.centos.noarch.rpm (type in your rpm version)

Import the CentOS 7 rpm gpg key
# rpm --import http://ftp.plusline.de/centos/7.0.1406/ ... Y-CentOS-7

Run the upgrade tool
# redhat-upgrade-tool --network 7.0 --instrepo http://ftp.plusline.de/centos/7.0.1406/os/x86_64/

Should this warn you that you didn’t run the upgrade assistant, you can force its execution by adding the extra option:
# redhat-upgrade-tool --network 7.0 --instrepo http://ftp.plusline.de/centos/7.0.1406/os/x86_64/ --force

A successful run ends with this message: “Finished. Reboot to start upgrade.“

Reboot

After restarting the machine, the OS will boot a new grub entry called System Upgrade which is supposed to upgrade all packages previously downloaded by the upgrade tool.

[[you may run into a small problem here “Database environment version mismatch” likely caused by the rpm tool itself (rpm version is 4.11 in CentOS 7 and 4.8 in CentOS 6).
solution:
# cd /mnt/var/lib/rpm
# rm __*
# init 6
Remove the rpm database files and reboot (CTRL+D or exiting the shell should also work as that would exit the emergency mode and continue from the last step before the error occurred) and the upgrade will get through without other issues.]]

# cat /etc/centos-release
CentOS Linux release 7.0.1406 (Core)

That's it.. Hope it helped..

[Emma Hickam]

Hi Vipin,

I am trying to upgrade my desktop OS. Will it work on both desktop OS and VM OS..

[Vipin]

Hello Emma,

This is only a proof of concept, it may possibly not work by default in production environments or on the Desktop, so use with care. For my test I used a fully updated base installation of CentOS 6.5 VM running on VirtualBox.

[Emma Hickam]

Hi Vipin,

So is it better to try the upgradation on a virtual machine before implementing it on the desktop ?? ...

[Vipin]

Hello Emma,

Yes. It is considered to be the best practice to implement anything on VM before implementing it on your base machine.