This chapter provides instructions on how to manually upgrade to HDP 2.5.5 from the HDP 2.1.0 release. It assumes the existing HDP 2.1 was also installed manually.

	Important
	If you installed and manage HDP 2.1 with Ambari, you must use the Ambari Upgrade Guide to perform the the HDP 2.3 to HDP 2.5.5 upgrade.

These instructions cover the upgrade between two minor releases. If you need to upgrade between two maintenance releases, follow the upgrade instructions in the HDP Release Notes.

The HDP packages for a complete installation of HDP 2.5.5 consumes about 6.5 GB of disk space.

Starting with HDP-2.2, HDP supports side-by-side installation of HDP 2.2 and subsequent releases, which lets you perform rolling upgrades on your cluster and improve execution times for in-place upgrade. To support side-by-side installation, the HDP package version naming convention for both RPMs and Debs has changed to include the HDP product version. For example, hadoop-hdfs in HDP-2.2.4 is now hadoop_2.2.4.0.hdfs. HDP-2.2 marked the first release where HDP rpms, debs, and directories contained versions in the names to permit side-by-side installations of later HDP releases. To select from the releases you have installed side-by-side, Hortonworks provides hdp-select, a command that lets you select the active version of HDP from the versions you have installed.

However, because HDP-2.1 did not support side-by-side installation, you upgrade to HDP-2.3.0 in a way very similar to previous minor-version upgrades. Subsequent upgrades after 2.5.5 is easier, and if you choose to add Ambari to your cluster, you can able to use the Rolling Upgrade feature.

	Important
	You cannot perform a side-by-side rolling upgrade from HDP 2.1 to HDP-2.5.5; only upgrade in place is supported. Side-by-side and rolling upgrade support starts with releases HDP 2.2 and above.

	Warning
	Until the upgrade is finalized, no HDFS data is deleted from the cluster. Be sure to review your capacity and ensure that you have extra space available during the upgrade window.

	Important
	You are strongly encouraged to read completely through this entire document before starting the Manual Upgrade process, in order to understand the interdependencies and the order of the steps.

The following steps are required to upgrade from HDP-2.1 to the latest release of HDP-2.5.5: