LTSP Workabout 27th June 2010
The Linux Terminal server is much talked about these days but just what is LTSP, is a free and open source add-on package for Linux that allows many users to simultaneously run on the same computer. Applications run on the server with a terminal known as a thin client. This was a workshop that some colleagues of mine and I decided to learn what we could about LTSP.
There where a number of prerequisites that we needed to enlighten ourselves with before we could proceed to install this LTSP server application. LTSP is available across all Ubuntu derivatives and may extend to other distros but which one to choose. The server we intended to use was a Xeon HP DL380 G4 very much overkill for what we wanted to achieve but it was spare, available and already fitted with all the components needed for a successful installation. Finally, the client and it occurred to at least one of us that only computers that use wired networking and that have PXE. The Preboot eXecution Environment (PXE, pronounced pixie and also known as Pre-Execution Environment) is an environment to boot computers using a network interface independently of data storage devices or installed operating systems. Wireless booting across the network is not possible as the drivers needed to operate wireless communication are not yet installed. However using a usb or floppy to boot from such drivers could be installed, we decided against this option on this occasion.
Here is a list of components we decided to run with for you reference:
- Alternate Ubuntu installation CD
- Xeon 64 HP DL380 G4
- Network Hub or Switch
- Some network cables
- Asus Eee notebook
- A Dell 1521 Laptop
- And another Dell Laptop I at present have no details of
This made up the sum of our equipment and software we needed to proceed with the LTSP installation.
By far the easiest way we could find to install LTSP was straight from disk and the "Alternate Ubuntu CD 10.04 LTS (Long Term Support)" seemed the best choice as we were installing to a 64Bit Xeon we choose the AMD64 alternate installation, we thought this may be a server install but it became apparent later this was a Desktop installation, not ideal distro choice for a server, still it will do for now.
Using "K3b" very important that, we burnt a CD with "Ubuntu Alternate ISO" this can be hard to find so suggest you search google for "ubuntu mirrors" and find the appropriate ISO for your server installation i386 or AMD64.
If you are considering an installation to a server similar to ours be aware that it comes with an integrated "Lights Out NIC" many but not all servers are equipped this way or a "Lights Out NIC card" this can cause some frustration if you are unfamiliar with networking. You see it has three network ports so which one is which, hmm! Additionally the server is built somewhat differently to a PC it has for instance 6 SCSI drives that are hotswapable such drives need to be configured so be sure you know how to proceed before deciding on a HP DL380 G4 or similar server.
- Install the CD into the server and boot from it
- Select from list available the language you want to use in our case English
- Find and press F4
- Locate "LTSP Server Install" and select it
- You will be prompted many times during this installation for your choices, it is assumed you have developed your knowledge sufficiently to configure and install your server from displayed options
- After selecting F4 on your keyboard nothing will happen until you have pressed enter you may need to press the enter or return key more than once to start installation process
- You will now be asked for your country option and keyboard selection make these choices as required
- Now you will need to define your Network options the only one you need define is the attachment to the wider area network have your network details to hand one of the ethernet ports is used for internet the other for local network and PXE booting!
- Disk parameter options come next "I think" choose automatic option if in any doubt it may not be ideal but will work
- Enter your name and logon details next along with your password
- Lastly you need to decide on a Grub installation to MBR (Master Boot Record) - that should be it nothing else should be required except a reboot which the server will do itself
If your installation has proceeded without problem you should after rebooting. The server would have configured itself with everything needed but then, their are those pesky ethernet ports, how many! This is perhaps the most difficult part of the installation configuration especially if you have only a little knowledge of networks. But be patient and you should be able to see it all through.
- Allow the server to boot and logon using your username and password
- Open a new terminal this is located in Applications => Accessories => Terminal
- type the following command and not the characters preceding it this is called the prompt
- Make a note of the ip addresses you should have one for each network remeber you have two Network cards now type Make a note of this to
- There are certainly more than one way of telling if your network is communicating but I find none more telling than nslookup <website_name> so type this command next the website of course will need to be valid. If the website name resolves to an IP address then you are half way there if not move one of the ethernet cables to a different port removing any ethernet cables in it's place. Essentially switch them about with one another. Now test again your connection and check if it resolves to an IP address.
- Now check that a dhcp signal and address is received this you can do with a different computer a laptop perhaps, check all your cables are in place you should have one from your server to a router switch or hub and from your hub/switch to your Laptop or PC. Boot your Laptop or PC nornally with the network cable from the hub/switch into it, your aim is to obtain an ip address if you are using linux ifconfig will give you the address check this value falls within the range documented previously.
Configure your Laptop or PC to boot using PXE this you can do within the bios of the Laptop or Computer you may also need to select boot options during the booting process to select the PXE network option.
This is a great way to deploy a large number of PC's to use the same default applications and configurations whilst only having one machine to administer, however there are some draw backs you should be aware of.
- You need to physically attach your computer via a cable
- It seems that despite it is using compressed images it can only handle it's own builds from its own distribution
- It does not seem to be flexible enough to handle different image types of the same package ie i386 and AMD64
- It cannot handle directly a build from a different OS except perhaps in vmware
- The minimum number of Network NIC in the server is two
- Many options are available via command line that could impair the function of the server
- Profiles need to be manually installed for each new user to the system
- Flash dependant sites consume a large amount of resources across a cable network which may interfere with other users twenty users would swallow all available bandwidth to the detriment of other users