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VMware allows Linux to be used for most commodity computing, while providing access to another operating system, such as MS Windows, running inside a Linux X Window. The guest operating system would be a full, standard version of MS Windows, allowing documents on the Linux filesystem to be edited with MS Office applications.
We are planning to maintain a basic MS Windows setup automatically for those users who simply require the standard Office applications. Users requiring more control over their MS Windows setup, such as external networking, or the ability to install other applications, would be able to maintain their own MS Windows image.
VMware is program which runs under Linux (or NT) and emulates the hardware of a standard PC to provide one or more virtual machines. Many operating systems can be installed on these virtual machines so that it is possible to run, for example, Windows 95 inside a standard X Window under Linux. It is even possible to run a complete Linux installation (maybe a different version) inside another window, at the same time!
Since the emulation occurs at a low level and runs standard operating system software, there are no additional problems with software compatibility. When running Windows 95, for example, a Windows licence is required and it is the real, full operating system that is running. The operating system believes that it is running on real hardware and speaking to real devices.
In general, the performance is very good and many applications appear to run as fast as on a native machine. A few applications may however have special problems - in particular programs which interface closely with devices (parallel storage media or MIDI) and, possibly some programs requiring high performance graphics.
A well-configured machine is required for acceptable performance - at least 400MHz with 128Mb RAM. Sufficient space is also required for the disk images of the additional operating systems - typically about 500Mb for Windows 95 with MS Office. A single VMware license is currently $77 (per-user, not per-machine), but we are hoping to be able to provide a full site license
A normal installation of a Microsoft operating system requires a long manual process to configure the system to the specific hardware of the machine. This means that the same installation can not be used for another machine which usually has different hardware. Since VMware emulates the same set of virtual devices on any machine, a single operating system image can be used.
It is also possible to configure VMware virtual disks in a read-only mode, so that changes to the filesystem are written to a separate log file, rather than being written back to the disk image. When the virtual machine is shut down, the changes can either be discarded or committed back into the disk image. This allows a single disk image to be used without any fear of it being corrupted. It also allows software to be installed experimentally with the installation only being committed if it is successful.
The DICE project aims to provide support for management of Linux systems, and we expect most users to use native Linux software for their commodity computing, however, many users have a demand for Microsoft applications and VMware should allow us to support this at several levels:
VMware can be installed automatically on required machines, together with a pre-built read-only version of some Microsoft operating system and Microsoft Office. The user would be able to access all the files on their Linux system using any Office application. Since the Microsoft image would not be changed, it would not require backup, would never be corrupted, and would be updated automatically as new versions became available. No effort would be required from the user to maintain this configuration. This would be ideal for those users simply requiring the ability to process MS Office documents - we believe that the majority of Microsoft demand falls in this category.
If a user wishes to make changes to the operating system, such as installing extra software in a persistent way, then they would need to take their own copy of the virtual disk. This would then require backup, and could not simply be updated with a new standard image when the core software was changed - in this case, it would be the user's responsibility to update their own image as required.
A default installation would only communicate with the Linux host, allowing user files and programs to be stored in the normal Linux filesystem. In some cases, it might be necessary to configure the virtual machine to communicate directly with the external network. We would not expect this to happen by default because of the security implications, and because of the need to configure the Microsoft networking by hand. Users requiring this would need to configure their own systems, as above.
