Is there documention to perform an OS upgrade form CentOS 6 to CentOS 7 on a multi nodes cluster?
I was thinking to:
1) Update to lastest CDH version on all my nodes
2) Retired a datanode of my cluster ( since i want to rename the server also )
3) do the OS fresh install ( since we go from centOS 6 to CentOS 7 )
4) Add the node back to the cluster - at this point i will have a cluster with mixed OS nodes. for couples of days ....
5) Is there specific instruction for the namenode ?
Is this managed by Cloudera Manager if so is ti parcel or packages based install?
As long as the parcels are deployed+activated, mount/directories for CM (/var/run/cloudera-scm-*) and CDH services (ie: HDFS/dfs.data.dir, dfs.datanode.data.dir,dfs.name.dir; Zookeeper/var/lib/zookeeper; etc) remain unchanged on your host, and are available when you bring up the cluster, there's shouldn't be any issues.
> 5) Is there specific instruction for the namenode ? see  or 
Back up HDFS metadata using the following command:
hdfs dfsadmin -fetchImage local directory
Let me know if this helps,
 Step 1. "4. Back up the HDFS metadata on the NameNode machine, as follows."
If you have not done already.
I followed the below approach.
1. I did the OS upgrade one by one
2. First move all the services(data node,node manager,etc...) from that node to other nodes. Delete that host from CDH cluster.
3. Upgrade the OS from centos 6 to centos 7
4. Now install the cloudera manager agent in centos 7 which will connect to cloudera manager server running in centos 6.
5. Here the problem comes. Cloudera manager server will not be able to distribute the CDH parcles to the new centos 7 server because of the os version mismatch. I already have the CDH distribution for centos 7 in my staging environment. I copy those in to production (centos 7) under /opt/cloudera/parcels. So now CDH distribution is available in centos 7 server. I just restarted the cloudera agent in centos 7 and it was ready to join the CDH cluster.