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Overview of JumpStart Server Components

The JumpStart framework is a client/server architecture with a number of server components that provide services throughout the installation process. The following table describes the high level components of a JumpStart system.

TABLE 1 JumpStart Server Components

Install Client

The target system to be installed or upgraded.

Boot Server

The network entity which provides a fail-safe OS to the installing client. The boot image is architecture neutral providing base OS services to all hardware supported by that OS release.

Configuration Server

Helps the client determine its unique profile. Partition sizes, the list of software to install, begin and finish scripts, etc. are all specified in a profile served by the configuration server.

Install Server

The source of the software packages which are to be installed on the client.

In practice, all three JumpStart servers are often located on the same physical host, but this is not a requirement.

Booting a client over the network is initiated when that client broadcasts a RARP request. Being an IP broadcast request, it is not typically forwarded beyond subnet boundaries. A server responding to this request, maps the client's MAC address to an IP and hostname, returning this data to the client. The booting client is now aware of two IP addresses: its own, and that of a RARP server. In order to simplify the network booting algorithm, the client assumes that any server which responds to the RARP request is also capable of responding to subsequent requests for data. As such, the RARP server is now declared the server for kernel delivery and boot parameter requests.

A system which provides all three services (RARP, TFTP, bootparam) is referred to as the boot server. The miniroot kernel is read from the boot server via TFTP. Once initially loaded to the client, the kernel will mount its root file system and begin processing with init, just as it would if booted from a disk. A similar procedure is used when using DHCP and a BOOTP relay for locating the installation client configuration information.

Even though the configuration and installation servers might be on separate hosts, on non-local subnets, it is important to note that the bootserver must be on the same subnet as the installation client. This requirement is due to the fact that RARP requests are not forwarded across subnet boundaries. It is because of this limitation on RARP requests that the JumpStart framework requires a bootserver (or a BOOTP relay if using DHCP) on the same subnet as the installation client.

The procedure described in this article provides a method to boot the installation client from a local CD or DVD-ROM and then use a configuration and installation server from the network.

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