Simplifying with NIM
How to use NIM.
Server consolidation is a major issue at many businesses with larger servers running multiple LPARs, all of which need to be installed, backed up and maintained over long periods of time. Since it takes several hours just to install one server from scratch using CDs or DVDs, clearly there has to be a better way to perform these mundane tasks. Implementing on demand capabilities means that the necessary resources are available to quickly build an LPAR from either a backup or a master image and to repeat this process whenever necessary.
Additionally, cost effectiveness for backups becomes a major issue when dealing with multiple clients. The cost of the client software alone can be prohibitive when trying to backup the OS on multiple client systems. The answer to these problems (for the OS at least) is to use the Network Installation Manager (NIM) to install and maintain the LPAR images as well as to take care of mksysb backups of the images. This article will explain what NIM is and how it can be used. (Note: In a future article, I'll discuss setting up a basic NIM server.)
What is NIM?
NIM has been around for a long time on AIX, and I have not-so-fond memories of it from the beginning of my SP days. However, in AIX 5L v5.3 several improvements have been made to NIM, including the ability to support Linux clients.
NIM basically provides a central point of management for installing and maintaining AIX images for both LPARs and individual servers. It also facilitates the installation of all of those instances from either the same master image (also called the golden image or gold master), from different images, from installation media or from a previous mksysb of that instance (instance refers to an OS image, regardless of whether it's an LPAR or on a dedicated machine). Additionally, NIM can group instances and install multiple instances at the same time across the network or by using the Virtual Ethernet facilities provided by POWER5 hardware and AIX 5L v5.3.
Setting up a NIM environment requires a NIM master and the number of client instances. The NIM master owns and provides the resources necessary for the clients to be serviced. All NIM operations on clients will require one or more of these resources. The master stores information about NIM and its setup in its own NIM database, which must be backed up regularly, and it stores the resources in ordinary AIX file systems. These file systems are available to clients using NFS.
NIM depends on certain protocols and network services in order to function correctly. These include NFS, bootp or DHCP, and tftp. Previously it also required the use of rsh and the other rcmd commands, but in AIX v5.3 it's now possible to use either basic nimsh or Openssl--either of which is more secure than the r-commands. These new services come as part of the bos.sysmgt.nim.client fileset, and the old rcmds are still supported in AIX 5L v5.3 for compatibility purposes.
The NIM master has certain minimum requirements. For example, it must always be at the highest level of AIX that it's required to support. That means that if you want to support a NIM client at AIX v5.3 ML3, then the NIM master must be installed with at least that level of AIX. The master can be at a higher level but it can't be at a lower level. The master can be an LPAR or a stand-alone server. Either way, it requires access to sufficient memory and processor power to support the required systems, and it requires a fast network to allow network installations to proceed quickly and smoothly. The master needs access to a CD or DVD and some kind of tape system to back itself up to. The CD/DVD is required to copy installation media into the necessary directories for pushing out installations. The master also requires sufficient disk space to provide space for the necessary resources for the clients, as well as the backups of their rootvgs.