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RedHat 6 to RedHat 7 upgrade


Upgrading RedHat from RHEL6 to RHEL7


So far we have been upgrading minor versions (say from rhel 6.5 to rhel 6.8) and the only way to upgrade a major version was to reinstall and restore. Now for the first time Redhat 7 is supporting in-place upgrade from rhel6 to rhel7.


1.Prerequisites

  1. Make sure that you are on running on the latest minor version (i.e rhel 6.8).
  2. The upgrade process can  handle only the following package groups and packages: Minimal (@minimal), Base (@base), Web Server (@web-server), DHCP Server, File Server (@nfs-server), and Print Server (@print-server). 
  3. Upgrading GNOME and KDE is not supported, So please uninstall the GUI desktop before the upgrade and install it after the upgrade.
  4. Backup the entire system to avoid potential data loss.
  5. If in case you system is registered with RHN classic , you must first unregister from RHN classic and register with subscription-manager. 
  6. Make sure /usr is not on separate partition.


2. Assessment 

Before upgrading we need to assess the machine first and check if it is eligible for the upgrade and this can be done by an utility called "Preupgrade Assistant". 

Preupgrade Assistant does the following:
  • Assesses the system for any limitations such as package removal etc.
  • When run this will generate an assessment results in the html format.
  • This will not change anything on the system except for storing some information.
  • We can run this tool multiple times until all the issues get resolved.

2.1.  Installing dependencies of Preupgrade Assistant:

Preupgrade Assistant needs some dependencies packages (openscap ,  openscap-engine-sce, openscap-utils , pykickstart, mod_wsgi) all these packages can be installed from the installation media but "openscap-engine-sce" package needs to be downloaded from the redhat portal. 

If you see the screenshot below i am trying to install preupgrade assistant without installing dependencies.


Install the dependencies first and if you see the screenshot below its alerting us that the package openscap-engine-sce is missing.
So i have downloaded the "openscap-engine-sce" rpm from the redhat portal and installed it.

2.2.  Installing Preupgrade Assistant

Now install preupgrade-assistant and preupgrade-assistant-ui packages




   
Install additional packages preupgrade-assistant-el6toel7 and preupgrade-assistant-el6toel7-data 







3. Running Preupgrade Assistant

Now we are all set to run the Preupgrade Assistant.On the command prompt run "preupg" command.











4. View Assessment Results

Now its time to check the results and the results can be found at /root/preupgrade folder.









Open the browser and type file:///root/preupgrage/result.html and scroll down to compliance and scoring.
























As said earlier in-place upgrades does not support GNOME and KDE desktops and even the OS should be upgraded to latest minor version.


5. Fix reported issues

Now we need to fix all the issues reported by preupgrade assistant.

5.1.  Remove GNOME and KDE Desktop:

Use "yum groupremove" to remove the GUI desktops.






















5.2.  Upgrade current OS to the latest version:

Execute "yum update" to update the current OS.















6.Run Preupgrade Assistant again

Make sure to resolve all the issues and run the "preupg" again.This time the "preupg" should not show up any failed components.






7. Perform the Upgrade

We are now set to upgrade the OS from RHEL6 to RHEL7 (please make sure to backup or clone your system before upgrading just to avoid any potential data loss).

Copy the redhat 7 iso locally and run the "redhat-upgrade-tool" to begin the upgrade. 








Reboot the machine to begin the upgrade.






After reboot check the OS version.









Hoping that this article has given a good hands-on experience on RedHat in-place upgrades!!!!
Feel free to Post your comments and i will get back to you as early as possible.




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