It sometimes seems that rate of change of operating systems is much much higher than the applications that run under them. This applies as much to Linux as it does to Windows, though there is considerably less financial pain involved there than in attempting to keep up with Microsoft. If you have to support an essential but elderly application that only works on one particular operating system, switching to something different may be a complete non-starter. Of all the ways out of this predicament, ‘machine virtualisation’ is both the most elegant and the lowest risk option.
Vmware is the market leader in virtualisation software for the PC, and its latest offering, Vmware Workstation 3.1, is available for Linux and Windows NT/2000/XP. This is a package that allows other operating systems to be installed and run as windowed applications that run on the desktop, in a similar way to Connectix Virtual PC.
It is possible, for example, to use Vmware to install a copy of Linux so that it runs under Windows 2000. This is not the same as dual-booting a machine; with Vmware the new operating system (referred to as the ‘guest’), runs as an application from the desktop of the main system (referred to as the ‘host’). Once the guest system is up and running it is possible to install applications in it in the normal way, including those applications which do not co-exist happily with the host.
Installation of Vmware Workstation 3.1 is very straightforward for a new install; upgrading from Vmware 2.x is considerably more complex, although the documentation is there to guide you through the numerous steps to uninstall and then install the upgrade. Once Vmware is installed it is possible to create any number of guest machines – the only constraints are disk space, memory and CPU power.
To create a guest system it is necessary to first configure a virtual machine – that is you create an image of a machine in which you will install a guest system. The configuration wizard leads you through the process fairly gently and any mistakes can be rectified later. Once configured it is time to boot-up the new machine, format the virtual hard disk (in fact a file on the real hard disk), and then install the guest system from CD or disk. The first time you have to format a virtual hard disk can be a bit scary, but the virtual machine does not actually erase any data on your real hard disk.
The range of operating systems that can be installed is fairly wide. In addition to most flavours of Windows and Linux, it is possible to create systems running DOS, Novell Netware, Solaris and FreeBSD.
Once installed, guest systems can be booted up and run whenever required. It is even possible to ‘suspend’ a system, close it, then load it back up at a later point in exactly the same state as when it was suspended. Sharing files between the host and guest system can be achieved by setting up a virtual network, which is a neat idea and does not even require the presence of a real network card in the host machine. Data can also be cut and pasted between systems. Running multiple guest systems concurrently is possible, but it requires a good deal of CPU horse-power to get the best performance.
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