StudentControlPanelSpec

Revision 5 as of 2006-10-22 11:40:14

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Summary

Roadmap for upgrading the implementation of student-control-panel

Rationale

To control LTSP connections in a school environment, an application that interacts with the ltsp server and the clients is needed. An initial implementation of this application tailored for the Ubuntu LTSP implementation called student-control-panel was uploaded to dapper. It currently implements basic connection control: it shows a list of the users and the ip each client they are using, allows the administrator to cut the connection for one, more or all users, and can show the currently running processes of a single user. The current scope is to control a standalone LTSP server, in case we start to implement clustering and the like, a network aware backend has to be implemented in a future version of student control panel.

More features are needed to provide a full student control application for school environments.

Use cases

Dr. Miller teaches biology in an ltsp equipped class. He has several students he suspects to secretly browse the web while he is not looking. Using student-control-panel he can monitor the students desktops via vnc to see if his suspicion is true.

Miriam teaches about free software in a class that uses a ltsp setup. She wants to demonstrate several free software apps she wants to start up on all students desktops. She hits ctrl-a to select all students in student-control-panel and clicks on the execute button which brings up a dialog to execute a command on all selected desktop simultaneously.

Anselmo has one student he doesn't want to be able to access the commandline from his desktop, since this specific student is known to write harmful scripts. Anselmo right clicks on the student's name in student-control-panel and selects the lock down option there. Pessulus, the gnome lockdown editor pops up and Anselmo checks the "Disable Commandline" checkbox.

Michael has several students who are not listening in his lesson, he presses the lock button from within student-control-panel and is able to lock the students keyboards and mice

Scope

Easy handling of student LTSP connections on a single LTSP server.

Design and Implementation

Plugin framework upgrade

  • The current student-control-panel plugin framework allows for server side only plugins. It would be advantageous to provide both server side and client side plugin components. The current framework uses a single class with a register function stored in a python module file. The proposed idea would be to modify the dbus routines to allow information to be passed back from the client to the server. This would then allow much more complex plugins to be created, such as chat programs and initiation of simple file transfers.
  • Many of the new proposed features could then be implemented over this plugin frame work

Update of GUI

  • Updating of many of the GUI elements of the current SCP such as
    • Button alignment
    • Simple/advanced for running application
    • Icons added to process window
    • Drop banner
    • Add menu / toolbar

Assistance Applet

  • Creation of a gnome applet that will act as an assistance helper for users. They will be able to click and ask for assistance. Possibly also used to drag and drop answers for a teachers specified question.

Blank / Lock Workstations

  • A system for locking keyboards and mice, as well as blanking a workstation would be a good idea. This could simply be achieved by starting the xscreensaver program on the clients machine but running as a different user. This would allow the password to be unknown to the client and the process could then be killed automatically by the server on removing the blank/lock restriction.

Generalisation of SCP

  • It has been recognised that SCP has applications outside of the school/education setting. It is proposed to rename the package and give it a more generic feel.

Remote desktop access

  • Student Control Panel will use vnc for remote desktop access. A function using the vncclient package is already completely implemented in the current student control panel code but disabled in the GUI since the handling on the LTSP client side wasn't clear yet; we will now fix that by adding a vnc server application (x11vnc) to the LTSP client chroot.
  • For the client implementation the x11vnc package will have to be installed in the client chroot.
    • The package will get a preseedable debconf option (suggestion: ltsp-client-mode), if this option is set to true, the postinst script installs an initscript which starts x11vnc connected to localhost:0 at boottime of the client and makes it read a custom password from a file thats located in the client chroot.
    • Student Control Panel will generate this password dynamically on every startup of the Student control Panel GUI (using PASSWORD=$(pwgen -c -n -s 20 1) should suffice here) and rewrite the password in the file. Since x11vnc reads the password on every new connection from that file it *could* affect existing Student Control Panel sessions. Because of this Student Control Panel will not start if there is already a running instance but spill a warning to first close the old one.
  • Since we dont want to run apt-get install from Student Control Panels postinst script in the LTSP client chroot, we can't just install x11vnc at install time of the student-control-panel package.
    • A "first start popup window" will be added to the GUI, with a checkbox "Dont show this window again" and a button "Install remote desktop access".

    • Choosing the latter option will execute a script /usr/share/student-control-panel/install-client-vnc.sh which will run  apt-get install x11vnc  in the LTSP client chroot with the above described option preseeded.

Outstanding issues

  • Determine the best default options (compression, scaling of the windowsize etc) for x11vnc to be added to the initscript by user feedback during developent.

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