Getting to know VMware

To keep you from having to buy specific hardware to run the demonstration system and to keep us from the impossible task of having to cover every possible combination of hardware we are using VMware Workstation. VMware Workstation is a great way to experiment with Linux, embedded Linux and other operating systems for the x86 platform. If you haven't heard of or tried VMware then you are in for a special treat. VMware has several different products, but it is VMware Workstation that is intended for use by developers and other technical users that is of interest to us here.

VMware Workstation gives us a virtual machine or PC sandbox in which to build and experiment with operating systems, applications and networking configurations. Based on virtual machine concepts from mainframe computers, VMware's MultipleWorlds technology is a thin layer of software that virtualizes the hardware resources of the physical machine. This includes the CPU, disk and many of the I/O devices. Standard Intel based guest OSes run within the virtual machines just as if they were running on a real physical PC. Multiple virtual machines can run concurrently, yet are strongly isolated from each other. You can even crash one guest operating system and the rest of the system will continue to run.

Figure 2: Two views of our software and VMware Workstation. The core software actually runs directly on the underlying hardware (top), but it also has a component that runs on the Linux host operating system. To a user, VMware Workstation just appears to be application software running on top of the host operating system (bottom).

VMware Workstation simply installs on a PC as if it was standard application software, although it is one of the most unusual pieces of software you are likely to use. There are two versions available, one for Linux and one for Windows NT or Windows 2000 systems. This operating system that your PC first boots is called the host operating system. Once you have one of the versions of VMware Workstation running the capabilities are much the same, independent of the host operating system. VMware software is fairly complex but luckily this complexity is hidden from the user. The core software actually runs directly on the underlying hardware and shares control of the physical PC with the host OS. There is also a component that runs on the Linux host OS. To a user, VMware Workstation just appears to be application software running on top of the host operating system, even though much more complex things are happening.

If you have enough RAM, you can run multiple virtual machines to build a network of connected systems entirely within one PC, allowing you to try out different client-server configurations without investing in a lot of hardware.

As VMware Workstation virtualizes I/O devices, the devices that appear within a virtual machine are usually not the same as those actually installed in the PC. This encapsulation capability provides portability. As you will see, we can take the disk image of an installed Linux operating system on the CD-ROM and install it in a virtual machine on your PC. We never have to worry about compatibility with the exact devices in your PC. For example, the Ethernet adapters within a virtual machine are always AMD PCnet-II devices regardless of the actual Ethernet adapter in the physical PC. The guest OS can use the host PC's serial and parallel ports and Ethernet adapters to communicate with external devices. Guest OSs can also access standard plug-in serial (COM) and printer (LPT) adapter cards. VMware Workstation however does not make general plug-in I/O adapters, such as data acquisition or GPIB adapter cards, available to guest OSes. But you can continue to use these devices with the host OS.

MultipleWorlds technology also extends the capabilities of the PC platform, so that virtual machines can do things that real physical PCs cannot. For example, VMware Workstation can add disk rollback-recovery suspend-to-disk and instant restore capabilities to standard OSs-features useful for developers. Other capabilities of VMware MultipleWorlds technology include being able to map the I/O devices that appear in a virtual machine to either real physical devices, to disk files, or to special files such as named pipes. This can be useful for debugging output from I/O ports and other development purposes. This is getting beyond what we can cover here but these advanced capabilities are very useful for developers, and we encourage you to explore them for yourself.

• Part 1: Introduction
  
• Part 2: What is LabVIEW?
  
• Part 3: Why use a desktop OS to build an embedded system?
  
• Part 4: Getting to know VMware
  
• Part 5: Six steps to Building an Embedded Linux System
  
• Part 6: Deploying on the hardware
  
• Part 7: Conclusion

 
This article was originally published on LinuxDevices.com and has been donated to the open source community by QuinStreet Inc. Please visit LinuxToday.com for up-to-date news and articles about Linux and open source.