Today in this post, we will look how to perform redhat or centos major release upgrade.
I. RHEL 5 to RHEL 6
a. In-place upgrades between major RHEL versions 4, 5 and 6 is not supported by Redhat.
b. Such upgrades do not preserve most of the system settings, services and custom configurations.
Hence Red Hat strongly recommends fresh RHEL installation when you are planning to upgrade from one major version to another.
Steps to perform upgrade
1. Download RHEL 6 DVD/CD iso and write it to device.
2. Insert the installation CD/DVD of the new version and enter below command at the boot prompt:
# linux upgradeany
II. RHEL 6 to RHEL 7
Redhat do not recommend and support such upgrade, however in rare scenario we can perform this migration using below steps.
1. Install required tools
# yum install redhat-upgrade-tool # yum install yum-utils
2. Disable all repos
# yum-config-manager --disable \*
3. Download latest RHEL 7 ISO from https://access.redhat.com/downloads.
And then upgrade to RHEL7 using ISO image downloaded.
# redhat-upgrade-tool --iso RHEL7_ISO_filepath --cleanup-post # reboot