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Contents

  1. Introduction
  2. Edubuntu Frequently Asked Questions
    1. About Edubuntu
    2. Edubuntu Help
  3. Thin Clients & LTSP
    1. I can login directly to the server, but I cannot log in to my thin clients.
    2. Where can I get good documentation on Edubuntu thin clients?
    3. What sort of hardware can I use for the thin clients and the server?
    4. Are there graphical management tools for the thin clients?
    5. Can I have some of my thin clients work as anonymous web kiosks?
    6. How do I modify the login screen on my thin clients?
    7. Sound doesn't work on flash applets (eg youtube videos) on my thin clients!
    8. Can I set up LTSP over a wireless connection?
    9. My Edubuntu server keeps filling up with files on /tmp!!!
    10. How do I set the root password on the thin clients?
    11. How can I automatically create large numbers of users?
    12. I can't get USB storage keys/devices to work on thin clients
    13. Thin clients prompt three times for password, even when the username is wrong.
    14. How do I lock down user desktops and other aspects of the system?

Introduction

This page answers some frequently asked questions about Edubuntu. The information is from the Edubuntu mailing lists, IRC channel, wiki, and other sources.

Edubuntu Frequently Asked Questions

About Edubuntu

Edubuntu is the education-focused variant of Ubuntu, with a fast and easy install, regular releases, and a tight selection of excellent packages installed by default, including education and productivity applications. An incredible variety of packages is available with a few clicks from a global network of mirrors, and professional commercial technical support from Canonical Ltd and hundreds of other companies around the world.

Edubuntu Help

Active community support is available, see https://wiki.edubuntu.org/Edubuntu/Community/Communication.

Thin Clients & LTSP

I can login directly to the server, but I cannot log in to my thin clients.

Try logging into the server and running: 

  • sudo ltsp-update-sshkeys

Then run: 

  • sudo ltsp-update-image

and reboot your thin client.

When your thin client logs you into the server, it checks the server's identity by looking at its ssh key. Most often, if the server's IP address gets changed, the key no longer matches and logins fail. The command above will update the list of keys and IP addresses.

More information on debugging logins can be found here: DebugThinClientLogin.

Where can I get good documentation on Edubuntu thin clients?

What sort of hardware can I use for the thin clients and the server?

Thin client hardware is discussed in detail here: https://help.ubuntu.com/community/EdubuntuDocumentation/EdubuntuCookbook/HardwareRequirements

Are there graphical management tools for the thin clients?

Yes. Under the System->Administration menu, choose Thin Client Manager.

Can I have some of my thin clients work as anonymous web kiosks?

Yes. You need to build a separate LTSP root environment on the server. The command to do this looks something like this: 

  • sudo ltsp-build-client --kiosk --base /opt/ltsp-kiosk/

Then, configure the DHCP server (/etc/ltsp/dhcpd.conf) to tell those thin clients to use the kiosk root by typing: 

  • option root-path="/opt/ltsp-kiosk/"

How do I modify the login screen on my thin clients?

The login screen on thin clients is generated by ldm running on the thin client. You can modify this, in the ltsp chroot environment /opt/ltsp/i386/usr/share/ldm/themes/ by making a copy of the theme, making your copy the default, and modifying the artwork 

sudo cp -r /opt/ltsp/i386/usr/share/ldm/themes/Edubuntu /opt/ltsp/i386/usr/share/ldm/themes/MyTheme
sudo rm /opt/ltsp/i386/usr/share/ldm/themes/default
sudo ln -s /opt/ltsp/i386/usr/share/ldm/themes/MyTheme /opt/ltsp/i386/usr/share/ldm/themes/default

Now just modify the images in /opt/ltsp/i386/usr/share/ldm/themes/MyTheme

Sound doesn't work on flash applets (eg youtube videos) on my thin clients!

This issue was a long-standing problem with the proprietary Adobe Flash Plugin. It has recently been fixed, although the fix did not make it into Edubuntu 7.04 (Feisty Fawn). The simplest way to fix this issue is to install the libflashsupport package on your server: 

sudo apt-get install libflashsupport

Can I set up LTSP over a wireless connection?

A short overview about how thin clients boot:

  1. thin client starts and sends a PXE or Etherboot request to the network
  2. DHCP server answers and tells the client where to get the kernel and the system from
  3. client pulls kernel via TFTP and mounts the filesystem via NFS from the server

WLAN cards don't support PXE or Etherboot, so there is no way for the thin client to send a PCE or Etherboot request to the network with a wireless card. The only way to achieve this would be to have the kernel and initramfs stored locally somehow (which indeed is not a LTSP setup anymore but rather a minimal local boot that mounts its filesystem via NFS). Additionally you would need to handle the ESSID for the WLAN as well as potential encryption via bootoptions.

It is not impossible to build a locally booting WLAN image, but you will always need local media (usb-stick, flashcard or CD) to boot from and it is far from being supported by us (implementing it will take some time and testing).

My Edubuntu server keeps filling up with files on /tmp!!!

This was a problem up to and including Edubuntu Feisty. They are old, temporary "swap" files from thin clients which were not shutdown properly. Adding the following line to /etc/hosts.allow:

nbdswapd: ALL: keepalive

should stop newly created files getting left around. You may find it easiest to reboot to clear the existing ones though.

How do I set the root password on the thin clients?

In order to debug individual thin clients it can be useful to be able to login in a text session on the thin client. To do this:

  1. Login as normal and start a terminal (under applications->accessories menu).

  2. Type sudo chroot /opt/ltsp/i386 and press return. You will be prompted for your password.

  3. At the next prompt, type passwd and press return. You will be prompted for the root password for the thin clients.

  4. If you're running gutsy (v7.10) or newer, you must now run sudo ltsp-update-image and reboot the thin client you wish to login to.

Having done the above, you can go to any of your thin clients, hold <ctrl><alt> and press F1. You should now be able to login with the username root and the password you set (if you see the message stating "your account has expired, please contact your system administrator" you must return to the chroot environment and issue the command passwd -u (unlock account) . You should then be able to login to the thin client, as the root user, using the password you set above.

How can I automatically create large numbers of users?

There isn't currently a way within the standard system "users and groups" manager tool. However, several ways exist which were mentioned in this thread on edubuntu-users mailing list.

https://lists.ubuntu.com/archives/edubuntu-users/2007-January/thread.html#529

most of the ideas centre around the createusers script which is part of Matt Oquist's smbldap setup script.

http://www.majen.net/smbldap/

I can't get USB storage keys/devices to work on thin clients

One of the most common reasons for USB storage devices not to work is the user needs to be in the fuse group. By running the groups command a user can check what groups he is in. You can change user groups in the user admin tool which you use to create users.

If that isn't the answer, there are instructions for debugging local devices here:

* https://wiki.ubuntu.com/DebugLocalDev

Thin clients prompt three times for password, even when the username is wrong.

This problem was discussed here: https://lists.ubuntu.com/archives/edubuntu-users/2007-November/thread.html#2636

To fix it, edit /opt/ltsp/i386/etc/ssh/ssh_config and add this line to the bottom: 

NumberOfPasswordPrompts 1

Then run: 

        sudo ltsp-update-image

and reboot your thin client. It should prompt for the username every time after that.

How do I lock down user desktops and other aspects of the system?

GConf is a good place to start. Here are some useful GConf keys to set as mandatory:

  • /apps/panel/global: locked_down
  • /desktop/gnome/background: picture_filename /home/share/backgrounds/picture.jpg
  • /desktop/gnome/lockdown: disable_lock_screen
  • /apps/metacity/global_keybindings: Go here to disable/set keybindings (such as removing the default ALT+F2 = run dialogue so students cannot arbitrarily run any program on the system)
  • /apps/gnome_settings_daemon/screensaver: start_screensaver
  • /desktop/gnome/lockdown: disable_user_switching
  • /apps/panel/global/disabled_applets: A list of applets you can disable. This was relevant when removing fast-user-switch and deskbar applets, as Gnome would complain upon login of every user that it couldn't load the applet (they are defaulted to load even when the packages are removed)
  • /apps/panel/toplevels/*/background: Will be good for setting panel translucency/color for administrator accounts

NOTE: If you are not familiar with GConf, please read up on it via the links below to understand how it works and how to set mandatory keys, as this is important if you want to lock down settings for all users.

Another lockdown option is to Hide the Filesystem structure in Nautilus.

And here is how to Set a mandatory homepage for all users in Mozilla Firefox ( Note: Please verify if this works on FF 3.x).

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CategoryFaq

EdubuntuFAQ (last edited 2011-06-16 04:50:57 by 24-151-190-2)