Cloudera Docs

Upgrading the Operating System

This guide provides comprehensive instructions for upgrading the operating system on hosts managed by Cloudera Manager. It outlines critical version compatibility checks, Java dependency requirements, and detailed procedures for both rolling and offline upgrade methods. Following these steps ensures a stable transition while maintaining cluster integrity and minimizing potential service disruptions.

Determining the Upgrade Sequence

You must first decide whether to upgrade the OS or Cloudera Manager. Consider an upgrade from Cloudera Manager 7.11.3 to Cloudera Manager 7.13.2, alongside an OS migration from RHEL 7.9 to RHEL 8 or 9:

  • Cloudera Manager 7.11.3 supports RHEL 7.9, 8, and 9.

  • Cloudera Manager 7.13.2 supports only RHEL 8 and 9.

In this scenario, you must upgrade the operating system first. Upgrading Cloudera Manager to 7.13.2 while still on RHEL 7.9 would result in an unsupported configuration and potential system failure.

Java Dependency Requirements

When migrating to a newer operating system, you must ensure your Java version meets the minimum requirements for both the OS and the Cloudera Manager version. Before proceeding:

  • Verify Compatibility: Check the Cloudera Support Matrix to identify the supported JDK for your target OS.

  • Maintain Consistency: You must synchronize the Java version across all cluster components, including Kafka brokers, ZooKeeper nodes, Active Directory (AD) integrations, and client-side environments. Discrepancies in Java versions across the cluster can lead to service instability or communication failures.

    Example
    When migrating to RHEL 8, you must update the Java version to at least OpenJDK 8. Ensure that Kafka brokers, ZooKeeper nodes, Active Directory (AD), and all client-side components utilize the same Java version to maintain compatibility.

Supported Upgrade Methods

Choose one of the two supported methods based on your downtime requirements:

Method 1: Rolling Upgrade

Cloudera recommends that you perform rolling operating system upgrades using prepared operating system images to replace existing operating system storage drives. During this process, you upgrade the operating system in batches by decommissioning hosts in a specific sequence. While this method might take longer than Method 2, it ensures the cluster does not experience downtime.

Method 2: Offline Upgrade

You must shut down Cloudera Manager and all Cloudera services to safely upgrade all hosts simultaneously. This method is faster but causes significant cluster downtime and carries higher risk, as any issues you encounter during the operating system upgrade might delay the restart of Cloudera Manager and the cluster.

This topic primarily describes essential manual steps, including backing up files and removing or reinstalling necessary Cloudera packages and parcels.