How to update RHEL, or centos major release version: from RHEL 5 to RHEL 6, or from RHEL6 to RHEL 7 ?

Today in this post, we will look how to perform redhat or centos major release upgrade.

Note:- The major release upgrade or migration from old RHEL/Centos Release to new one is not recommended and we advise you to take backup and install new system and restore it thereafter.

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

NOTE:– Red Hat currently supports upgrade only from Red Hat Enterprise Linux 6 to Red Hat Enterprise Linux 7 for some specific/targeted use cases.

And upgrade between any other version is not at all recommended and supported by Redhat.

References:

https://access.redhat.com/documentation/en-us/red_hat_gluster_storage/3.4/html/installation_guide/rhel6_to_rhel7
https://access.redhat.com/solutions/21964

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