Classroom Model

LliureX distribution aims mainly at providing all the Valencian Educative Centres with a computing room that features all the necessary resources to support the teaching task using only free software.

To that end, LliureX develops a Classroom Model which assumes that there is a classroom server for either all thin clients or workstations connected to the same local area network. The server has been set up with an additional external network connection which allows to be connected either to the Internet or to the rest of the centre internal network.

Since it is basically centred on the classroom , the deployment process is simplified due to the fact that the classroom model has been developed with the main purpose of implementing LliureX classrooms in all those centres already provided with an IT infrastructure.

At first, the network topology required might be as represented below:

Connection to the Internet is made through broadband links. Currently, broadband connections shall be provided by ADSL lines which will be connected to a fixed line router with a public IP address so that all Pcs in the educative centre can gain access to the external network through the proxy server.

The LliureX classroom computers cannot be accessed via a web browser and, for now, only the server will have both direct Intranet and Internet access.

EThe classroom is provided with a server connected to both the school and the classroom networks.

Clients shall be run in different modes,

• As a network client, the PC starts up using an operating system installed on the hard drive though it uses the server to get all the available configuration data (IP address, users data, DNS and so on) and to have access to the whole space where users files will be stored.
• As a thin client, the PC runs a minimum system start-up and graphic session is started in the server.
• As a workingstation, the PC starts up a local operating system so it does not use either the network or the server. In fact, this mode would be used in case of not having a server.

The classroom server provides the client Pcs with different services such as the basic and necessary ones to run the network clients and the additional ones which might be used by teachers whenever they need, depending on the task to perform.

Available Services in the Classroom

he classroom shall have the following services available:

• User identification: data backup and recovery. Typically, users are listed either in the /etc/passwd file or in /etc/shadow. However, LliureX includes network authentication services using the server session key so all the client equipments connect to it so that the users can be identified.

  Though there are several ways of providing these authentication services, most of them are currently performed by the PAM library (Pluggable Authentication Modules) which is enabled at client applications and by modules configuration to validate keys through the database. This information is stored in a LDAP server because of its protocol´s versatility and the variety of tools for its simple administration.

• Name service provided: Linux include multiple database services which provide information on users, groups, service and computers names and so on. Normally, these databases were stored in text files in the different operating systems but right now, a standard system handles these data bases from different sources. This scheme is called NSS (Name Service Switch) and, as PAM does, it allows the use of modules. Databases are stored in a LDAP server and the nss_ldap module is used to handle data. The DNS service is provided by a specific server though it uses the LDAP data.
• IP dynamic configuration: a DHCP server assigns private network data addresses to the different clients to get the client configuration data.
• Network files server: all documents, configurations and user files are stored in the classroom server.

The main goals to be achieved are:

• Independent work stations.
• Thin clients containing no local storage capacity.
• Simplification of the backup process.
• Access to files either through the Linux or Windows workstations.
• Integration with LDAP authentication system: To use LDAP a Samba File Server package is installed and the clients will make use of PAM modules to set up the user root directory and the autofs configuration files for common directories.
• Backup system: if two hard drives are available, daily incremental backups are managed on the second hard drive. Though this does not provide full protection against hardware faults, the recovery of data accidentally deleted is guaranteed as well as a low cost data recovery when disk faults.
• Support to thin client systems.
• Operating system restoration.

In addition to the above mentioned, the following services are included in the standard installation:

• Network print server.
• SQL database management system.
• Web server (http / https)
• Web service for e-learning.
• Proxy cache with optional filtering.
• Public file server (mirrors).
• Instant messaging system.

Technologies to be used so as to provide classroom services:

• Users authentication.
• Name services.
• IP dynamic configuration.
• Network file server.
• Backup system.
• Support to thin client systems.
• Operating system restoration.