Tutorial

Basic LTSP Terminal

The simplest (‘purest’) form of an LTSP terminal comprises a PC configured to boot from an LTSP server. When the terminal boots, it downloads the necessary LTSP client software from the LTSP server into memory, and from then on runs as a self-contained diskless X Terminal. This is by far the simplest form of terminal to configure and manage, and runs well on most standard specification PCs, including those which are considered obsolete by users of Microsoft Windows. A list of supported thin clients is available.

Other variations of LTSP Terminal

However, the LTSP package does provide some support for PCs that are either fall below or exceed the standard specification.

• PCs with as little as 4Mb of memory can be made to work as LTSP terminals by mounting a swapdisk on an NFS server. This makes an otherwise unusable PC usable, at the cost of additional load on the server and additional complexity (terminals have to be configured on a case by case basis).

• At the other extreme, a high spec PC with a fast CPU and generous amounts of RAM can run an X server and have lots of spare capacity. One way to use this capacity is to run one or more X client applications locally on the diskless X terminal. This reduces the load on the LTSP server, especially if applications malfunction, and can enable users to run graphics intensive applications, or application needing access to peripherals attached to the terminal. Another option to powerfull clients is the openmosix + LTSP scheme, in which you basically create a cluster out of the server and diskless terminals, and at the same time they are all usable as workstations.
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Note: applications have to be specially analysed and set up to run on the terminals. The server environment becomes more complex and less secure, with sharing of users files via NFS and authentication via NIS. Users also lose the benefits of code sharing.

For most situations, the default configuration of LTSP terminal provides the greatest benefits of terminal/server computing.

Minimal Specification of an LTSP Terminal

The hardware requirements for the terminal are modest:

CPU	RAM	Performance
i486-66	16Mb	acceptable
P75	24Mb	good
P133	24Mb	good
>P133	>24Mb	not noticeably better

The client also needs:

• a floppy disk drive to boot from (or a bootable network card);
• an Ethernet card or onboard Ethernet adaptor supported by Etherboot
• and a reasonable graphics card with 2Mb of video RAM for a full graphical user desktop (old monitors may work better at lower resolutions, allowing lower spec video - e.g. 1Mb video RAM can produce 812 x 608 at 16 bpp)

It helps if the video and network card are PCI, as most PCI devices can be automatically detected by the software (ISA require manual configuration).

Support for Peripherals attached to the LTSP Terminal

The X server on the terminal manages the standard parts of the user interface: graphics; keyboard, mouse, and also some more exotic devices like touch screens. In the simple model, all other peripherals are provided by the server.

However, LTSP does provide some support for other peripherals attached to terminals, either out of the box or using additional software:

• Printers: networked printers are standard in Linux; so permitting printing to printer attached to a diskless X terminal is simple to set up for serial, parallel, or USB attached printers
• Soundcards: common types are supported through an optional component to the standard LTSP package.
• Floppy disk drives and CD-ROMs: can be accessed over the network, using add-on components (but only for file storage - e.g. playing of audio CDs is not supported)
• Scanners: are supported via the Sane Package for LTSP 4.1 or packages found here: LBE-compiled Sane Packages for LTSP 4.1

Converting a PC into an LTSP Terminal

If a networked PC meets the basic specification of an LTSP terminal, converting it can be as simple as identifying the network card installed, inserting the appropriate Etherboot floppy disk and rebooting the PC. Once the PC has booted, the floppy disk drive is then no longer required until the next reboot.

The process is completely reversible, making it comparatively simple to set up ‘proof of concept’ demonstrations as long as one PC is available to be used as an LTSP server.

Pros and cons of LTSP

See ProsAndCons for the strengths and weaknesses of LTSP.

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