Re: RFC/Discuss: Replace KDE by LXDE on LTSP?

[Knut Yrvin <knuty@skolelinux.no>]

On Torsdag 30. april 2009, Vagrant Cascadian wrote:
> do you still see a speed improvement using KDM vs. LDM with
> LDM_DIRECTX=True ? this feature still uses ssh for the initial
> connection (i.e. namely, the password negotiation),

I haven't heard about computer administrators testing that. What I've 
heard is an other story that you already know. 

Many schools are running LTSP thin clients on really old or cheap 
computers with scare resources. We saw this in Norwegian schools three 
years ago, when upgrading to Skolelinux 3.0 with LDM. Half of the clients 
stopped working, or become to slow. 

The reason was twofold. Many clients got only 32 MB RAM. LDM used around 
50 MB RAM to run. The clients got a black screen when booting, even if the 
LTSP started nicely in the first place.  Also, clients with 64 MB RAM did 
not run smoothly when having a ssh tunnel running, cause the added 
computational power needed to decrypt the traffic. 

Then computer administrators downgrade to a prior version of LTSP without 
LDM. Or else 250 machines that worked easily with Skolelinux 2.0, just 
stopped working when upgrading.  Luckily the schools in this example got 
additional grant last year to buy new machines. Now they run Low Fat 
clients (diskless) on most machines. Their bottleneck experiences then 
vaporised. That said, it's a greater perspective here. 

Some computer administrators has told us that the security level provided 
with a switched network is more than enough for them. Since we are 
providing netgroups bound to a MAC address, you can't get root access to 
the network with a random connected laptop. It's a bigger problem that 
kids have written their password on a note in their pencil case. A Note 
that can easily be red by a fellow student. 

An other school system admin told me: If a 14 year kid is able to do 
package sniffing on a switched network, we should consider commending them 
instead of sending a not home to their parents on how to behave. 

My take on this, is that's much more to be gained speeding up other parts 
of the boot sequence. LDM or KDM is not the real time thief's if you're 
looking ahead. It's often before that in the boot process, starting 
services not needed, the file system (as shown with speed improvements 
between ext3 and ext4) etc. 

It's put into play a whole lot of resources now from Ubuntu, Mandrive, 
Nokia, Intel, KDE, Gnome etc. to make Linux boot really fast, having full 
power management capabilities (sawing power), with a full fledged desktop 
system. Initiatives as Maemo, Moblin and KDE Plasma points in that 
direction. This improvements has already been committed upstream to 
different projects, and will finds it's ways into Debian sooner than later.

We are soon in a luxury situation, to make the right blend of options. 
Earlier we had to do a lot of plumbing to make things integrate nicely. Of 
course plumbing are still necessary. But we also got much more solutions 
ready than before. Now we can make a laptop, netbook or mobile Internet 
device work together with a Skolelinux or a K12LTSP network pretty easy. 

It's often about taking small chunks of code already made, and integrate 
that to the standard network solutions provided with school distroes. I'm 
helping out with such initiatives just as we speak. A student project are 
working with the network manager code shipped with many Linux 
distributions. This work is committed to Debian through alioth, but also 
upstream to the network manager repository. 

Best regards

Knut Yrvin
-- 
Skolelinux, relation manager
cell: + 47 934 79 561, phone: +47 21 60 27 58
http://www.skolelinux.no