Lessdisks, LTSP, workstations, VNC, NoMachine NX, FreeNX (Was: Workstation Maintainance?)

[Finn-Arne Johansen <faj@bzz.no>]

Sorry, for the long subject, but I feel some need to clarify some
thoughts. 

Lately there has been much talk about workstations and diskless and
thin client setups. I'm not the developer behind thos different
solutions, but because of my employment in the department of education
in Oslo (the cpital of Norway) and my involvement in creating a working
Sarge-based Debian-edu, I have looked at different solutions in
optimizing the workstations in Debian-edu. To simply, the picture, I
think we have 7 basic types of installations:

Main servers - giving basic services such as authentication, home
  directories, printing, email, dns, dhcp and others
Terminal servers - Giving thin clients the possibility to run
  applications such as mozilla an OpenOffice
Boot servers - Giving diskless machines a kernel and a root filesystem
Workstations - where people work with Mozilla and OpenOffice and such
  applications
Multimedia Workstations - where people work with scanners, image
  manipulations, music, films and such
Thin Clients - Workstations that boot off boot-servers, and where they
  work on a terminal-server
Laptops - Where people can take a working solution and bring it home,
  without the need for a connection to the main-servers.

In Skolelinux we have 
main - a main-server with all the services (it's hard to spilt them)
workstation - Actually this is more like a Multimedia workstation,
  because everything is installed, and since we dont care about the
  license cost why bother to diffrentiate?
Thin-client-server - basically a combination of workstation, Terminal
  server and a boot-server
Standalone - some would call this a bastard, but it works for laptops,
  but do you really want to run woody with kde 2.2 on a laptop?

Thin clients comes when network booting from the Thin-client-server, so
we've got that covered as well. 

Then some "Products": 

LTSP - The solution used to set up thin clients in Skolelinux. In our
  case the boot server and the Terminal server is the same, and
  filesystem for the thin clients are exported using nfs. LTSP 3 was
  built by taking pieces from various distros, mostly from RH6.2, and
  creating a root file system of it. LTSP 4 is built from sources,
  using its own build environment, where you need 2 GB of sources, and
  a total of 5 GB disk to build, and you have to be root while
  building. (not even sure if sudo will do, fakeroot is not enough)
Lessdisks - Something quite similar to LTSP, but uses debian packages
  to create the root filesystem. Maybe a bit larger filesystem is
  exported, and not so optimized libraries, but a lot easier to
  upgrade. security patches the debian-way. while lessdisks are in fact
  a thin-client solution today, I have done a proof of concept, using
  some hours, to create a diskless setup with lessdisks using recycled
  PC with PIII 500MHz with 128 MB memory as workstations, and an old
  PII 266MHz Toshiba laptop with one PCMCIA-nic and one usb-nic as a
  server. No problem at all watching video in avi format, or running
  flash applications in mozilla. I have estimated somewhere between
  200-400 hours to get a working solution with debian-edu. where we use
  lessdisks to create diskless workstations capable of running as
  normal workstations (not multimedia workstations where you edit huge
  images, edit video or sound, but capable of running flash and java
  and stuff). This will make way for boot servers that may server more
  thin clients with less memory/cpu. 
FreeNX - A Citrix/ICA like technology for Linux. not a replacement for
  LTSP or lessdisks, but more an enhancment. With NX, you may run the
  application server on the other end of an old modem line, and you may
  still run applications like OpenOffice and Mozilla on top of KDE, and
  get a workable solution. But dont you dare to run
  multimedia-applications on top of that. Then you will need more
  bandwidth. Actually I've watched videos over my DSL line with this,
  but without sound. It should also be possible also be possible to get
  sound working, and to get file and print over samba to work, but I
  have not succeded. You may need NoMachine NX for that. 
NoMachine NX - The commercial part of NX, and the origin of NX. You may
  buy support from them. I suspect that it may be easier to set up
  file/print/sound sharing using NoMachineNX. They are really nice
  people to talk with. 
Systemimager - This makes it possible to create images for installing
  on many machines. It also makes upgrades on many workstations easier,
  we are already using this on ~100 laptops on Ulsrud, where the
  laptops may be upgraded automaticly whenever they are started each
  day. (we dont upgrade them each day of course)
  For more info, please look at:
   http://developer.skolelinux.no/dokumentasjon/installing_SL_to_a_laptop.txt
   http://skolelinux.no/~finnarne/debian-edu-sysimg/README.debian
FAI - well here I'm blank. I know Kurt loves it. I know it is really
  fast in setting up new machines, and I know it supports LVM, which
  systemimager does not. But I dont think it's usefull for updating old
  installations. I know someone has said so, but I'm not sure. but
  anyway, installing overagin on normal workstations should not be a
  problem. 

Then lets look at different techniques to maintain the various
installation of skolelinux-machine-profiles. 

I like to diffrentiate between servers and workstations/laptops. 

On servers, I prefer to have cronjobb running, with the following tasks 
  apt-get -qq update
  apt-get -qq autoclean 
  apt-get -qydu dist-upgrade
That way I get an email from the server telling me what should be
updated, and which server it comes from (okay, I've added som logic to
this one...)

Then I might log in to the server, and do the upgrade manually, I used
to have my own server on which I upgraded things first, and then
checked, but now that server(s) is busy working with something else.
But on the other hand, we dont play around with our packages that much,
so basically, things should be safe. 

The laptops I've set up, is set up using systemimager, and yes,
although we are doing 5 or 6 different laptop types, all with different
soundcard, nic (both wire and wireless), graphic cards and cpu flavour,
We are using the same image on all of them. What we do is that we
create an image, then install on all the others. THen we take one of
the laptops, and upgrades that one, check that things are okay, and
then upgrades the rest the next morning when the students log in. 

Depending on the number of workstations, I would either used the server
model (if this was the one machine that had all extras like scanner,
videokamera, ++) and do the upgrade manually, or if this was a classrom
full of workstations, I would have used the model we uses for laptops.
But instead of upgrading whenever the machine gets turned on, I would
have a cron-job checking for upgrades each morning or something. 

Peter Reinholdsen has mentioned dsh, and in fact dsh is distributed on
our server profile. But I'm not sure how much dsh is in use. I have
searched the net for a description on how to use it, and found
something like: 
 first do the upgrade on one machine
 then copy /var/cache/config.dat to every other machine
 then run apt-get upgrade through dsh on the other machines, and
 debconf has already gotten all the answers. 

You might need to make sure that debconf only asks unseen questions.
And I guess you need to have identically setups/machines. 

Okay, what about diskless installations, using FAI or lessdisks or
LTSP? 
When it comes to LTSP, I feel that while LTSP has proven quite capable
of things, it will still only remain a thin client solution. I know
NoMachine has a setup where they uses LTSP, and I know that LTSP know
supports rdesktop, I feel that LTSP is not capable of running
applications like OpenOffice and Mozilla locally. Well, It's capable,
but I dont want to have the responibility of security patching thos
apps. When it comes to diskless workstations running OpenOffice,
Mozilla and KDE locally, I would rather use lessdisks, As I have no
experience with FAI, but I think it could be used. 
These workstations could do everything that dont need a huge swap disk.
given that you have enough memory. In fact, lessdisks could be used for
that as well, but lessdisks (as of today) needs a local disk for swap. 
Some of the documentation for FAI indicates that it might be used as
diskless setup as well.

Disclaimer 
This email has gotten so long that I forgot why I started it. 
I also forgot why I put in VNC in the subject line, but ....
I started this email this morning, and kind of finished now. I guess
I'll be back with more when I remember why I started this. 
But if I kill this email now, I will regret it later
/Disclaimer

-- 
Finn-Arne Johansen 
faj@bzz.no
http://bzz.no/