JavaStation Client Software Guide

Chapter 1 Planning the JavaStation Environment

This chapter introduces the JavaOS operating system, describes JavaStation hardware, and explains the requirements you should understand before configuring your network to administer JavaStation computers.

JavaStation Overview

The JavaStation network computer is a new type of computing device that provides application processing power but does not store software or data. The JavaStation computer relies on servers throughout the network for its boot information and software. The JavaStation environment is composed of several JavaStation clients and the server(s) that administer them. This figure shows a simple network configuration in which all the services required by JavaStation computers reside on a single server.

Figure 1-1 Sample Configuration of a JavaStation Network



  1. Internet or intranet

  2. Sun server with home directories, boot, NIS, DNS, web, and DHCP services

  3. JavaStation computers

The JavaStation computer's uniquely open software platform enables it to replace existing stateless devices, such as dumb terminals, and to bring high-performance computing to environments where it was not used before.

This chapter gives an overview of setting up a JavaStation network, addressing the following key topics:

JavaOS Operating System

The JavaOS operating system is specifically designed to run network computers such as the JavaStation computer. The compact architecture of the JavaOS software provides the following advantages:

Statically Linking the User Application to JavaOS

The JavaOS operating system supports linking of application files to the JavaOS binary via a special build you can execute at the command line. The JavaOS image resulting from the new build can be downloaded to JavaStation computers in exactly the same way as the old image, with exactly the same core functionality. However, in addition, the user application will be launched automatically when the JavaOS software boots.

Static linking is useful when the JavaStation computer is a public kiosk or other fixed-function device running a single, dedicated application. For instructions on using the static link procedure, see "Using SLK".

Dynamically Loading the User Application in JavaOS

Dynamic loading is similar to static linking, in that it enables the user application to be launched immediately when the JavaOS software boots. However, in this case the application is not physically linked to the JavaOS image; rather, the JavaOS software finds and downloads the application from a network server via HyperText Transfer Protocol (HTTP) immediately after it boots. Because HTTP is used to download the application, the application can reside anywhere on the network that is visible to the JavaStation web server.

The dynamic loading scenario is not limited to a single application. If you like, JavaOS can open a dialog window with a list of applications for the user to choose from. When the user selects an application, JavaOS locates and launches it.

Dynamic loading works in any situation where the JavaStation computer has web access. For instructions on using the dynamic loading procedure, see "Setting Up Dynamic Delivery of an Application ".

JavaStation Hardware

JavaStation systems are available in two distinct models as shown in the figure below. The first-generation "brick" model (left) is recognized by its rectangular shape. The newer "tower" (right) sits vertically on the desktop and features a striking, swept profile.

Figure 1-2 JavaStation Systems from Sun


Brick Model

The first-generation brick model JavaStation computer includes the following features:

Tower Model

The second-generation tower model JavaStation computer includes the following enhancements to the original model:

JavaStation Model Comparison

As shown in the table below, the first-generation "brick" JavaStation computer must download JavaOS from a boot server over Ethernet. These computers are appropriate for local-area network (LAN) deployment where 10Base-T Ethernet networking is available.

The second generation "tower" JavaStation computers are ideal for remote or Wide Area Network (WAN) environments in addition to local 10Base-T and 100Base-T LAN environments. The integrated flash RAM enables these JavaStation computers to be installed remotely and deployed across a WAN or corporate extranet.

Table 1-1 JavaStation Comparison for LAN and WAN Environments


Brick Model JavaStation 

Tower Model JavaStation 

Target Environment 


  • LAN

  • WAN


Network boot 

  • Network boot

  • Flash RAM



  • 10/100Base-T

  • PPP over telephone line

Network Services

This section gives an overview of the network services required to administer JavaStation computers. Although all of these services can be configured at the Solaris command line, the Netra j web-based administration interface provides a simpler way to configure them. For information on the Netra j software, visit or peruse the Netra j 3.0 Administrator's Guide.

The JavaStation computer requires the following network services for boot information and software.

Table 1-2 JavaStation Network Services


What It Does 

DHCP (Dynamic Host Configuration Protocol)  

Delivers configuration information to the JavaStation computer, including the JavaStation computer's IP address and the addresses of the other servers it requires.  

TFTP (Trivial File Transfer Protocol)  

Delivers the boot file to the JavaStation computer. May deliver JavaOS to the JavaStation computer. 


Provides access to the user's home directory on a server. May deliver JavaOS to the JavaStation computer.  

DNS (Domain Name System)  

Provides address resolution for systems throughout the Internet. 

NIS (Name Information Service)  

Provides lookup for user names, home directory location, and print servers.  

RAP (Remote Authentication Protocol)  

Provides lookup for user names and home directory location. 

HTTP (HyperText Transfer Protocol)  

May deliver the user application to the JavaStation computer. Delivers web pages and Java applets to the JavaStation computer. 

The figure at the beginning of this chapter shows a simple network configuration, whereby all the services required by the JavaStation clients reside on a single server. In contrast, a JavaStation network with distributed services might look something like the figure below.

Figure 1-3 JavaStation Network With Distributed Services



  1. Internet or intranet

  2. HTTP (web) server

  3. NFS server

  4. DNS/NIS server

  5. DHCP/TFTP server

  6. JavaStation computers

The following sections give an overview of each service required to administer JavaStation computers. For detailed descriptions of these services, see "JavaStation Boot Sequence".


DHCP is used to pass IP addresses and configuration information to diverse host systems on a TCP/IP network. When a JavaStation computer is powered on, it receives initial boot information from a DHCP server that is configured to deliver specific parameters to JavaStation computers. The same DHCP server may also be configured to deliver different information to other systems on the subnet.

One server on the JavaStation subnet must be configured with DHCP services or configured to relay these services. If all JavaStation clients reside on the same subnet, and if there are no other DHCP servers on the subnet, no other configuration is needed.


TFTP is used along with NFS during the network boot sequence to download a "booter" and (optionally) JavaOS over the network to the JavaStation computer. There is no need to guard against conflict with other TFTP servers on the network.


Strictly speaking, NFS is only required by the JavaStation computer to access and save user data and preferences information. Once a user's home directory has been determined via the NIS automounter map (auto.home), it is mounted using NFS. The default user applications provided with the JavaOS software (HotJava Browser, HotJava Views) only use NFS to read and update preferences information. However, many commercial applets may need to use NFS to access and save data files in the user's home directory.

NFS is also the default mechanism used to provide the JavaOS network boot download for the JavaStation computer. It is important to note that the network boot download can alternately be achieved with TFTP through DHCP directives, which may be useful for JavaStation clients used as fixed-function devices (such as kiosks or point-of-sale devices). However, NFS is much faster than TFTP for this purpose.


The JavaStation computer uses DNS to provide address resolution for host names. Using DNS ensures that JavaStation applications and applets can access URLs either on the corporate intranet or across the Internet.

DNS lookups from the JavaStation computer are rather infrequent, so the load on the DNS server will be relatively small. The JavaStation boot server can be configured as a DNS slave server if a central DNS server for the domain is busy or remotely located.


The JavaStation computer uses NIS for user authentication, file mapping, and printer access as follows:

NIS lookups are infrequent, and the performance impact is not likely to be significant. When binding to NIS, a broadcast is sent to the local network. This implies that there must be a NIS server connected to that network. If necessary, the JavaStation boot server can be set up as a NIS slave server or master server. You can also specify the NIS server's IP address in the DHCP parameters delivered to JavaStation computers.


The JavaStation computer can use RAP instead of NIS for user authentication if it has been configured to do so and if a RAP server exists on the JavaStation network. In return for the user name and password, RAP provides the following:

With this information, JavaOS can mount the user's home directory via NFS.


HTTP can be used to deliver the main user application to the JavaStation clients. HTTP is also used by the JavaStation clients to browse the corporate intranet and sites on the Internet.

Proxy Cache

Most corporate intranets implement a secure HTTP proxy system comprising several HTTP servers. The way the proxies are set up can have a significant impact on JavaStation browser performance. If a single proxy server is used for a large number of users, it can become a bottleneck and a single point of failure. If it is located at another site or across a busy backbone network, it will greatly increase the response time for network requests from the JavaStation computer. One solution to this problem is to make the JavaStation boot server into a proxy cache for its clients.

Understanding the Boot Sequence

Most of the remaining chapters in this guide explain concepts and procedures related to booting the JavaStation computer. Chapter 2, JavaStation Boot Process: Theory of Operations gives a basic overview of the entire boot process, while the other chapters provide supporting information or specific details on one or two procedures. Use the list below as a reference to all the booting information in this guide.