Upgrading CDH 4
You can upgrade to CDH 4.1.3 (or later) within the Cloudera Manager Admin Console, using parcels and an upgrade wizard. This vastly simplifies the upgrade process. In addition, using parcels enables Cloudera Manager to automate the deployment and rollback of CDH versions. Electing to upgrade using packages means that future upgrades and rollbacks will still need to be done manually. Upgrading to a CDH 4 release prior to CDH 4.1.3 is possible using packages, though upgrading to a more current release is strongly recommended.
The following instructions describe how to upgrade from a CDH 4 release to a newer CDH 4 release in a Cloudera Managed Deployment. If you are running CDH 3, you must upgrade to CDH 4 using the instructions at Upgrading CDH 3 to CDH 4 in a Cloudera Managed Deployment.
To upgrade from CDH 4 to CDH 5, see Upgrading from CDH 4 to CDH 5 Parcels.
Before You Begin
- Before upgrading, be sure to read about the latest Incompatible Changes and Known Issues and Workarounds in the CDH 4 Release Notes.
- If you are upgrading a cluster that is part of a production system, be sure to plan ahead. As with any operational work, be sure to reserve a maintenance window with enough extra time allotted in case of complications. The Hadoop upgrade process is well understood, but it is best to be cautious. For production clusters, Cloudera recommends allocating up to a full day maintenance window to perform the upgrade, depending on the number of hosts, the amount of experience you have with Hadoop and Linux, and the particular hardware you are using.
- To avoid lots of alerts during the upgrade process, you can enable maintenance mode on your cluster before you start the upgrade. This will stop email alerts and SNMP traps from being sent, but will not stop checks and configuration validations from being made. Be sure to exit maintenance mode when you have finished the upgrade in order to re-enable Cloudera Manager alerts.
- Impala - If you have CDH 4.1.x with Cloudera Impala installed, and you plan to upgrade to CDH 4.2 or later, you must also upgrade Impala to version 1.2.1 or later. With a parcel installation you can download and activate both parcels before you proceed to restart the cluster. You will need to change the remote parcel repo URL to point to the location of the released product as described in the upgrade procedures referenced below.
- HBase - In CDH 4.1.x, an HBase table could have an owner that had full administrative permissions on the table. The owner construct was removed as of CDH 4.2.0, and the code now relies exclusively on entries in the ACL table. Since table owners do not have an entry in this table, their permissions are removed on upgrade from CDH 4.1.x to CDH 4.2.0 or later. If you are upgrading from CDH 4.1.x to CDH 4.2 or later, and using HBase, you must add permissions for HBase owner users to the HBase ACL table before you perform the upgrade. See the Known Issues in the CDH 4 Release Notes, specifically the item "Must explicitly add permissions for owner users before upgrading from 4.1.x" in the Known Issues in Apache HBase section.
- Hive - Hive has undergone major version changes from CDH 4.0 to 4.1 and between CDH 4.1 and 4.2. (CDH 4.0 had Hive 0.8.0, CDH 4.1 used Hive 0.9.0, and 4.2 or later has 0.10.0). This requires you to manually back up and upgrade the Hive metastore database when upgrading between major Hive versions. If you are upgrading from a version of CDH 4 prior to CDH 4.2 to a newer CDH 4 version, you must follow the steps for upgrading the metastore included in the upgrade procedures referenced below.
- Parcels - You can upgrade from an earlier version of CDH 4 to a newer version of CDH 4 using parcels. Upgrading using parcels is the recommended way to perform a CDH upgrade—the upgrade wizard handles most of the details of the parcel and configuration upgrades. To upgrade to a newer version of CDH 4, see Upgrading CDH 4 Using Parcels for instructions. If you have a Cloudera Enterprise license, are performing an upgrade between CDH 4 versions, and have enabled HDFS High Availability, you can optionally follow the rolling upgrade procedure.
- Packages - If your current Cloudera Manager-managed clusters were installed using packages, you can elect to upgrade your CDH installation using packages. For instructions, see Upgrading CDH 4 Using Packages).