Edubuntu - Linux Terminal Server project (LTSP)

This page is intended to report tests and evaluation of Edubuntu server and LTSP functionalities in order to set-up a Linux terminal server and associated thin-client (diskless) stations in the conditions of Vietnam. This could be especially useful for schools and places, like in the countryside, where old low-resource computers still in order to function can be found but are not strong enough to run modern operating systems and softwares.

In a server and thin-client setup, users are sitting at a thin client, but they are running a session on the server. All commands they run, will be run on the server, but the output will be displayed on the thin client. Thus the server should be a strong computer (a fast CPU, lots of RAM - 256 MB for itself and 128 MB per client - and a good and robust hard disk). See the theory of operation.

Ubuntu server 7.10 at CNF-AUF, Nov. 3rd, 2007

Because we did not yet downloaded the iso files of Edubuntu 7.10 server and serveraddon, on Saturday 3rd November 2007 David installed Ubuntu server 7.10 on a test machine (Pentium IV Celeron 2.26 Ghz, 512 MB DDRAM 400 Mhz, 40 GB ATA hard disk, VGA INTEL 915 on board with memory sharing, RTL 10/100 LAN onboard as eth1 and Realtek PCI ethernet card 10/100, as eth0).

Installation was without problems. The LTSP package has to be installed and it was quite a lengthy process as many applications had to be downloaded for installation on the server. We could boot a thin-client station but were yet unable to log on (logging was refused). As it was already late in the afternoon, we stopped the test to resume the next Saturday with Edubuntu server 7.10.

The thin-client used for the test was an ordinary computer of the CNF center, rather similar to the “server” (Celeron 2.26 Ghz, 512 MB DDRAM 400 Mhz, set to boot on LAN as first device - PXE boot), so quite overfit as a true thin-client as requirements for the thin-client are a 400 Mhz CPU and 128 Mb RAM.

Edubuntu server 7.10 at CNF-AUF, Nov. 10th, 2007

We started the Edubuntu server installation on the same test server without problems. Installation seemed more lengthy than for a normal Ubuntu desktop, about one hour, instead of about 30 minutes.

Following instructions on the Edubuntu site, and after configuring the ltsp.conf file, we created several user accounts on the server and used the same test thin-client to connect to the server without any problems. Then, we connected a second thin-client and both were running applications at a satisfactory speed.

photo of the Edubuntu server, in the middle, and two thin-client stations A closer view of one thin-client logged on the server

The only problem, until now, is the detection of local block devices on the thin-client. For example when you would insert an USB drive on the thin client, it would be detected by the kernel on the server but would not be mounted locally on the thin-client. This seems to have been a know issue for previous versions of Edubuntu, which did found a solution. So we will continue further testings the next week.

  • It's the local kernel that detect hardware changes, not a remote one. – ProgFou

Troubleshooting 1 : no log in possible

The last setting made on Saturday 10th November was probably wrong somewhere. When I booted the Edubuntu server on November 13th, the two ethernet cards had the same network's adress in the form of 192.168.1.0/24. So I changed the /etc/ltsp/dhcpd.conf file to provide a different network's adress to the thin clients : 192.168.5.0/24. In this case, the Edubuntu server was connected to the internet through its eth0 card (192.168.1.148) and was distributing IP adresses to thin-clients through DHCP by listening on eth1 (192.168.5.254) in the range of 192.168.5.20 to 192.168.5.250.

Doing so, the thin clients received rightly an IP adress in the form of 192.168.5.xxx but logging users was no more possible : message returned back was “This workstation isn't authorized to connect to the server”.

After doing some research on Google, I found this page and followed the instructions : “run commands sudo ltsp-update-sshkeys and sudo ltsp-update-image (in this order)”. AFter doing so, I rebooted the thin-client and this time all went OK : log in was possible !

Troubleshooting 2 : black screen on thin-client

We had problems in booting some thin clients configurations which was deceiving at the first approach. Especially with this configuration : A second-hand Fujitsu mini-box (Pentium III 866 Mhz, 128 MB SDRAM, 10 GB hard disk, Slim CD drive and Foppy drive) that sells on the market right-now for about 750.000 VND (end-user price).

Typically, after the boot of the thin-client, you got the IP adress from DHCP, a splash screen and immediately after you got a black screen with only the horizontal prompt blinking at the upper left corner of the screen.

Gavin Mc Gullagh hinted to a similar problem posted by Mike White on the edubuntu-users list :

Mike White : PXE booting and screen goes black just before I get to the login screen...
Gavin McGullagh : A couple of things to try:
1. Specify the colour depth in your lts.conf to be 24, or failing that 16.
/var/lib/tftpboot/ltsp/i386/lts.conf
eg

[00:11:25:93:CF:00]
  X_COLOR_DEPTH = 16

2. If the above doesn't fix, try making your boot verbose.  Edit
/var/lib/tftpboot/ltsp/i386/pxelinux.cfg/default and remove the words "splash" and "quiet"

So I checked the lts.conf file and saw it was absent in the ”/var/lib/tftpboot/ltsp/i386” directory, I issued a “locate lts.conf” command and saw it was at two locations in ”/opt/ltsp/i386/lts.conf” and ”/opt/ltsp/i386/etc/lts.conf”. After checking the content to conform with instruction 1 from Gavin Mc Gullagh, I just copied the lts.conf file to the place where it was missing as indicated by Gavin Mc Gullaugh :

sudo cp /opt/ltsp/i386/lts.conf /var/lib/tftpboot/ltsp/i386/

Then I removed “slash” and “quiet” from the file /var/lib/tftpboot/ltsp/i386/pxelinux.cfg/default

old Fujitsu used as thin-client

After that, the Fujitsu mini-box “magically” booted completely, up to the login screen !

Troubleshooting 3 : no local mounting of devices

We did succeed, later, to mount USB drives on thin-clients. But we did not documented the procedure right away and now I have forgot how we did. But this is not important because right now we have switched to the next, the newest vesrion of Edubuntu, i.e. Hardy heron 8.04.1

Ubuntu 8.04.1 LTSP at CNF : August 2008

OK. After being busy for many other things, it's summer time and we have some (little) spare time again. So let's have a look at how Edubuntu Hardy Heron 8.04 LTS had improved ?

The Ubuntu server

This time, we invested in a good computer. After reading all the posts received on the Edubuntu user's mailing list, we know we must invest on a strong machine. So we bought an Intel Duo Core E4500 (2.2 Ghz) CPU, with 3 GB of DDRAM and a SATA 3 GB/s 160 GB Hard drive. EN plus on the onboard Gigabit network card, We installed a second PCI ethernet card.

Installation was very simple, no problems at all, using the Ubuntu 8.04.1 LTS Desktop Alternate CD. We followed instructions on this page. Basically, at the Ubuntu CD's prompt, after choosing the language, the keyboard, you just press F4 to select the type of installation that you want. So here we chose LTSP server.

After installation of the basic system, we did all the package upgrades and tested thin-client connexions. Our eth0 (onboard network card) was connected to the LAN and received its IP address dynamically from the LAN's DHCP server. We set the eth1 ethernet card as static with a fixed address as “192.168.125.1”.

This is the content of the ”/etc/network/interfaces” file after modification (adding parameters for eth1):

 # This file describes the network interfaces available on your system
 # and how to activate them. For more information, see interfaces(5).
 
 # The loopback network interface
 auto lo
 iface lo inet loopback
 
 # The primary network interface
 auto eth0
 #iface eth0 inet dhcp
 
 # the secondary network interface (for LTSP)
 auto eth1
 iface eth1 inet static
 address 192.168.125.1
 netmask 255.255.255.0
 

We edited the /opt/ltsp/dhcpd.conf files as follows, basically replacing the default subnet address (192.168.0.0/24) by ours (192.168.125.0/24), so you just have to replace any occurrence of the string “192.168.0.” by “192.168.125.”, that's so simple:

 #
 # Default LTSP dhcpd.conf config file.
 #
 
 authoritative;
 
 subnet 192.168.125.0 netmask 255.255.255.0 {
     range 192.168.125.20 192.168.125.250;
     option domain-name "example.com";
     option domain-name-servers 192.168.125.1;
     option broadcast-address 192.168.125.255;
     option routers 192.168.125.1;
 #    next-server 192.168.125.1;
 #    get-lease-hostnames true;
     option subnet-mask 255.255.255.0;
     option root-path "/opt/ltsp/i386";
     if substring( option vendor-class-identifier, 0, 9 ) = "PXEClient" {
         filename "/ltsp/i386/pxelinux.0";
     } else {
         filename "/ltsp/i386/nbi.img";
     }
 }
 

First problem : login screen at low resolution (640×480) and login refused. The second problem was quickly fixed from our previous experience with Edubuntu 7.10, so we ran in a terminal the following commands:

 $ sudo ltsp-update-sshkeys
 $ sudo ltsp-update-image

And that's it : we rebooted the thin-client and login was successful. USB drives were recognized on the fly on the thin-client. Only remained the low screen resolution problem at 640×480. We'll deal with that problem later.

Now that the login was successful, we installed the server with more necessary packages to bale the thin-clients to work properly in our environment (Vietnamese French-speaking academic community).

Jean-Christophe André has produced a meta-package called “hanoilug-desktop” which helps in installing close to 200 packages and about 230 MB of downloads (read here how to install the Hanoilug repository), including Ubuntu-restricted-extras, Msttcorefonts, Java, etc. The result is a “functional” desktop for working in a Vietnamese environment, with English (US), French and Vietnamese language environments.

After installation of the “hanoilug-desktop” meta-package, we did again the update of the LTSP image and started to test connections of various computers as thin-clients. We discovered that some computers could boot without problems while others would not receive the boot image : network cable quality was the cause ! using a good network cable solved that problem ! So do not hesitate to invest in good quality cables, especially the RJ-45 head connectors.

It Works !!!

You can see below a picture of the Ubuntu 8.04.1 LTSP server and of two different thin-clients logged in and playing two video (Youtube) files. The old Fujitsu PIII 667 Mhz, used above with Edubuntu 7.10, performed very well, we had sound, everything worked nicely. The Norhtec Microclient Jr. was rather slow, especially for the boot time to the login screen. Playing the video file was more or less ok, but launching Openoffice.org 2.4 was very quick.

Actually, there is a small mistake in this picture : the Fujitsu has a PIII 866 Mhz CPU and not 667Mhz as indicated. That should not be a problem for the performances. Such a CPU unit can probably be found on the second-hand market in Vietnam for about 30-50 $US by now.
The Norhtec Microclient unit was rather slow (several minutes to get to the Ubuntu login screen). Displaying one of the video was with very bad image (problems with the video chipset, I think) and the other one tested was more or less OK, image was not as fluid as with the Fujitsu but still acceptable. Norhtec is now providing new units, with 512 MB Ram, which should perform better but are more costly (190 $US instead of 120 $US for the unit tested). You can guess the USB drives icons on the Desktop of the two connected clients.

The good thing with Ubuntu hardy Heron LTSP was especially the successful mounting of local devices on the thin-client, like USB keys. Of course, there are still some (minor) problems with these USB devices :

  • unmounting USB drives : When right-clicking on the icon of the USB device on the Desktop, there was no choice for unmounting the device in the menu. If you open the device in Nautilus (the file explorer in GNOME), you could right-click the device and choose to unmount the volume. However, when doing so, umount generated the following alert : ”/media/disk-usb is not listed in /etc/fstab and you are not Root to be able to unmount it”). So we just chose to log-out before unplugging the USB drive.
  • Mounting plugged USB drives on the server resulted in the USB device icon appearing on the server's Desktop AND on the connected thin-client's Desktop. The connected user could not however open the device connected to the server in a Nautilus window.

In conclusion : the people from Ubuntu-Edubuntu have succeeded in giving us a very fine system which should work out of the box most of the time.

If you have comments and questions, you can write to me : vdquynh (at) gmail.com

 
projects/ltsp/edubuntu.txt · Last modified: 2009/12/22 19:13 by progfou
 
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