Difference between HMC Upgrade & Update

It’s important to distinguish between updating and upgrading a system. The terms are not synonymous. 

Upgrade
To upgrade is to bring the system to a higher version or release of HMC code. When the HMC’s version number is incremented, such as going from Version 6 to Version 7, the upgrade method must be used in order to apply the new version of HMC code.

Update (Corrective Service)
In between HMC releases, or between upgrades, there will be times when interim fixes or cumulative service packs need to be applied. Interim fixes consist of security fixes or fixes that are considered critical to be released immediately to customers. Service packs are generally larger in contents. Both can be installed on the HMC by using the Install Corrective Service task under HMC Code Update, or by using the updhmc command on the HMC.

HMC Roles for User IDs

HMC comes with two predefined users: hscroot and root and cannot be deleted. They come with default passwords, but it is strongly recommended that they be changed during HMC setup and configuration. The default passwords are:

Username: hscroot
Password: abc123

Username: root
Password: passw0rd

Note: Make sure you change them!

hscroot & root have all the access to HMC and can manage & modify almost everything in HMC. Logging in as root is disabled. Note that while you will not be using the root password for daily administration, you may need it from time to time when performing problem determination, usually with the assistance of IBM support or product engineering.

Apart from these accounts, additional user IDs should be created on the HMC so that not every user is accessing the system with the same user ID and password, and not necessarily with the same level of authority.

Each HMC user IDs can be a member of a different role. A task role in HMC defines the access level for a user to do tasks on the managed object or group of objects, such as a managed system or logical partition. HMC roles are either predefined or customized. 

When you create an HMC user, you must assign that user a task role. There are 5 system defined task roles:

•hmcsuperadmin - The super administrator acts as the root user, or manager, of the HMC system. The super administrator has unrestricted authority to access and modify most of the HMC system. This should not be confused with user root.

•hmcservicerep - A service representative is generally someone (from IBM) physically at the managed system location to install, configure or repair managed systems.

•hmcoperator - An operator is responsible for daily system operations, but do not have authority to add new users or modify the roles.

•hmcpe - A product engineer assists in support situations (for both the managed system and the HMC), but cannot access HMC user management functions. To provide support with access for your system, you must create and administer user IDs with the product engineer role. PE can additionally shutdown HMC & close virtual terminal windows which service rep can't do.

•hmcviewer - A viewer can view HMC information, but cannot change any configuration information.

Hardware Management Console (HMC)

A Hardware Management Console (HMC) is an Linux based appliance used to manage IBM Power Systems servers. HMC is used to:

• Add / Remove LPARs
• Manage logical partitions and partition profiles
• Perform Dynamic LPAR (DLPAR) operations. (DLPAR operations that change the resource allocation (such as processor, memory, physical I/O, and virtual I/O) dynamically for the specified partition)
• Activate and manage Capacity on Demand resources

We can perform above functions without rebooting the operating system running in the LPAR.

A single HMC can control multiple Power Systems servers and multiple HMCs can manage a single Power System. An HMC can be used via either an X-Windows graphical user interface (GUI) or an SSH command line interface (CLI).

An HMC is necessary only to manage Power Systems servers. Once configured, Power Systems servers continue to operate normally even if the HMC is shut down. But please note that larger Power Systems servers (Power 760 and above) require an HMC to successfully power up. Once a server is powered up, the HMC is no longer required for the server to continue to operate normally. An HMC also provides access to the console of every virtual machine (LPAR) on every managed server. 

As of July 2016, the latest version of HMC is V8R8.4.0 

Note: LPAR (Logical Partitioning) is a way of subdividing all of a computer’s resources, including the memory, storage, and processors, and splitting them up into smaller logical units that can each be run as a separate part of the operating system (OS)