Chapter 20. Upgrading Your OS From CentOS 6.6 to RHEL 6.6

To upgrade your OS from CentOS 6.6 to RHEL 6.6, we recommend upgrading in the following sequence:

Before starting the OS upgrade, stop your Ceph cluster. Execute:

sudo /etc/init.d/ceph -a stop

Once you execute with -a (i.e., execute on all nodes), Ceph should stop operating.

For ease of understanding, we will divide the upgrade section into three sub sections, viz:

20.1. Prerequisite
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Update your OS to ensure it runs the latest kernel available. Execute:
```
sudo yum update
sudo reboot
```

Install packages that will be required by various Red Hat Network tools:

sudo yum install dbus-python libxml2-python m2crypto pyOpenSSL python-dmidecode python-ethtool python-gudev usermode

Log into Red Hat Customer Service Portal with your RHN account credentials.
Click Downloads to visit the Software & Download Center.
Click on Red Hat Enterprise Linux to visit it’s download page.
Select Version as 6.6 from the drop-down list and click on Packages tab below.
Use the Filter text box on the right hand side, search for and download the latest version of the following packages for RHEL 6.6 x86_64 in your rhel directory:
- redhat-release-server
- rhn-check
- rhn-client-tools
- rhnlib
- rhnsd
- rhn-setup
- yum
- yum-metadata-parser
- yum-rhn-plugin
- yum-utils

Install the Red Hat GnuPG signing key:

cd /rhel
sudo wget https://www.redhat.com/security/fd431d51.txt
sudo rpm --import fd431d51.txt

Forcibly remove the package that identifies the current system as CentOS:
```
sudo rpm -e --nodeps centos-release
```

Forcibly upgrade to the downloaded RHEL and RHN packages:

sudo rpm -Uhv --force *.rpm
sudo rpm -e yum-plugin-fastestmirror
sudo yum clean all

Once, you have upgraded your OS to RHEL 6.6, start ceph from your admin node and check if it is running properly.

Execute:

sudo /etc/init.d/ceph -a start