Abstract:

The Castelo Branco Technology School is a public institution of higher education focused on engineering and technology, including several information technology programs, ranging from professional development to master degree level. One of its key values is a strong emphasis on the development of practical skills, supported by activities which take place at several dedicated laboratories.

One of these laboratories, the “Computer networks laboratory”, is used by several courses. It also hosts the Cisco Regional Academy, which is responsible for Cisco certified courses such as CCNA, CCNP and other Cisco programs. The laboratory has several bundles of networking equipment, including switches, routers and firewalls. Furthermore, there are 18 computers that can be used by up to 36 students.

The courses that use this laboratory have different requirements regarding operating systems and applications. This led the technical staff to install several operating systems on each computer, allowing students to select the desired operating system during boot. This strategy allowed multiple software profiles, but proved to be unpractical due to the following problems:

• Students had to have administration privileges in order to perform some tasks. This led to several problems, including software misconfiguration, file corruption, inappropriate software installation, malware and even partition table problems;

• Students that were not able to complete an assignment during a class were forced to restart the assignment from the beginning in the next class, because in the mean time other students changed the configuration;

• Each computer was able to run only one operating system at a time. This was a critical limitation, because some networking assignments require several machines;

• The technical staff had to permanently inspect each computer, in order to determine its operational status and perform a fresh install if needed;

These problems lead to the development of a new approach: using virtual machines. This new approach is supported by the Virtual Box framework on top of an Ubuntu Linux distribution. Now, students do not have administration privileges on the native operating system and must use virtual images during classes. Each computer has a read only directory with several images of virtual machines ready to be used. These virtual machines include several Linux distributions, Windows XP, Windows Seven and less known images such as TrixBox for VoIP.

The main advantages of this approach are:

• Students can still have administration privileges on their own images but not on the native operating system. Consequently the native system is always clean and stable;

• Students can save images on their personal area, or even in a pen disk, avoiding access from other students. This way, ongoing work can be resumed in the next class without the risk of unwanted changes;

• One physical computer can host several virtual machines with different operating systems at the same time;

• Virtual images can be updated and distributed automatically to the laboratory computers with a minimum effort;

The full paper describes the technical details of this approach, including performance issues, virtual network topologies and the automatic synchronization of virtual images. It also presents the feedback obtained from students and teachers regarding the advantages and disadvantages of this solution.

Keywords:

Virtual machine.