Using the SPOT resource

The Shared product Object Tree (SPOT) is a fundamental resource in the NIM environment. It is required to install or initialize all types of machine configurations.

A SPOT provides a /usr file system for diskless and dataless clients, as well as the network boot support for all clients.

Everything that a machine requires in a /usr file system, such as the AIX® kernel, executable commands, libraries, and applications are included in the SPOT. Machine-unique information or user data is usually stored in the other file systems. A SPOT can be located on any standalone machine within the NIM environment, including the master. The SPOT is created, controlled, and maintained from the master, even though the SPOT can be located on another system.

You can create a SPOT by converting the /usr file system (/usr SPOT, or you can locate the SPOT elsewhere within the file system (non-/usr SPOT) on the server.

The /usr SPOT inherits all the optional software that is already installed on the server. All the clients using the /usr SPOT have access to the optional software installed on the server. The non-/usr SPOT can be used to manage a different group of optional software than those that are installed and licensed for the server.

Creating a SPOT by converting the /usr file system has the advantage of being fast and using much less disk space. However, this method does not give you the flexibility to choose which software packages will be included in the SPOT, because all the packages and filesets installed in the /usr file system of the machine serving the SPOT will be included in the SPOT. The second method, creating a non-/usr SPOT, uses more disk space, but it is more flexible. Initially, only the minimum set of software packages required to support NIM clients is installed in the SPOT, but additional packages and filesets can be installed. Also, it is possible to have multiple SPOTs, all with different additional packages and filesets installed, serving different clients.

Note: Do not create a non-/usr SPOT in a subdirectory of the /usr file system.

A SPOT varies in size from 100 MB up to, and sometimes in excess of, 300 MB depending on the software that is installed. Because all device support is installed in the SPOT and the number of device filesets typically increases, the size is not easily predictable from one release of AIX to another.

SPOTs are used to support all NIM operations that require a machine to boot over the network. These operations are as follows:

  • bos_inst
  • maint_boot
  • diag
  • dkls_init
  • dtls_init

When a SPOT is created, network boot images are constructed in the /tftpboot directory of the SPOT server, using code from the newly created SPOT. When a client performs a network boot, it uses tftp to obtain a boot image from the server. After the boot image is loaded into memory at the client, the SPOT is mounted in the client's RAM file system to provide all additional software support required to complete the operation.

Each boot image created is up to 17 MB in size. Before creating a SPOT, ensure there is sufficient space in the root (/) file system, or create a separate file system for /tftpboot to manage the space required for the network boot images.

The Micro Channel-based systems support booting from the network using Token-Ring, Ethernet, or FDDI. The POWER® processor-based PCI bus-based systems support booting from the network using Token-Ring or Ethernet. The uniprocessor MCA and PCI bus-based systems can be used in a diskless or dataless configuration.

A single network boot image can be accessed by multiple clients; therefore, the network boot image cannot contain any client-specific configuration information. The platform type is specified when the machine object is defined, while the network type is determined from the primary interface definition. Two files are created in the /tftpboot directory on the SPOT server for each client to be network-booted: ClientHostName and The ClientHostName file is a link to the correct network boot image, while the file contains the client configuration information.

When the SPOT is defined (and created), the following occurs:

  • The BOS image is retrieved from archive or, for /usr conversion, just the root directory is retrieved from archive (/usr/lpp/bos/inst_root).
  • The device support required to support NIM operations is installed.
  • Network boot images are created in the /tftpboot directory.
To list the software installed in a SPOT, enter the following command:
nim -o lslpp SPOTName

If you want to change your /usr SPOT back to a normal /usr file system, you must remove the SPOT from the NIM database.

For information about software installation and maintenance tasks you can perform on a SPOT, see Customizing NIM clients and SPOT resources.