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.

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.

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.

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

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 !

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

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