Created on 10-06-2018 03:58 AM
Starting with HDP 3.0 release, Hortonworks has stopped CentOS 6 as a supported platform. This would mean existing cluster nodes needs to be migrated to CentOS 7 before install/upgrade to HDP 3.0. However, CentOS has no official support for upgrading OS from CentOS 6 to CentOS 7. This article provides an unofficial guide for migrating cluster nodes to CentOS 7 without losing data. This is downtime migration. We would strongly recommend trying these steps on test clusters. These steps are applicable only for a smaller cluster ( <= 10 nodes ) and larger nodes we would need different strategy + automation for the same.
Below are some of the assumptions or pre-requisite to be performed before upgrading the OS.
HDFS Data Node Directory ( dfs.datanode.data.dir) is pointing to non-root disk ( i.e. on mounted disk other than where OS is installed ) HDFS Name Node Directory (dfs.namenode.name.dir) is pointing to non-root disk Yarn Local Directories config (yarn.nodemanager.local-dirs) is pointing to non-root disk. Zookeeper dataDir is pointing to non-root disk. Oozie Data Directory is pointing
Migrating Slaves Nodes
Pick a slave node in the cluster for upgrading the OS. Please note each slave nods needs to be upgraded one at a time. Please do not attempt upgrading multiple slave node in a single go. Follow below steps to upgrade the slave node from CentOS 6 to CentOS 7.
Migrating Master Nodes
Upgrading the Master Nodes to CentOS 7 is similar to that of slaves node. Since this article covers upgrade with downtime, inline upgrading is out of scope. In case we are performing inline upgrade we would need to have HA for all master and move the components to different hosts before upgrading the same, however, this is out of scope from the article.
Migrating Ambari Node
Run below pre-requisite before upgrading the Ambari Node.
Post the pre-requisite is complete follow below steps for the actual upgrade.
Migrating MIT KDC
If the cluster is configured with MIT KDC and is installed within the cluster, follow below steps to backup and restore kerberos database. Please note kdc needs to be installed on the same host where it was installed before the upgrade.