Linux & Unix & the Virtual OS

Unix has been used since the 1960's and today, it by far froms the most used OS in the Internet backbone and that is because it is stable and a solid performer. Most Unix distributions are proprietary, closed systems and can be costly when compared to Linux. Midrange UNIX servers are priced in between $25,000 and $249,999 (including hardware). The major distributors are HP, IBM and SUN. A high end UNIX server can cost anywhere upward to $500,000.

On the other hand, Linux is an open source, Unix-Like, some say Unix-Clone type of Operating System(OS) which is free and widely used for computer hardware and software, game development, tablets, PC's, Servers and Mainframes and can be freely distributed.

User Mode Linux provides(UML) a powerful and flexible way to share multiple users, servers , resources on a single machine. UML is a basically a "virtual Operating System(VOS)". It is a special Linux OS running on the normal or Linux Host OS. The VOS is independent of the Host OS. The Host OS is executed directly on the hardware, the VOS operates like an application on top of the Host OS. Within the VOS, all work is similar to the Host OS including the installation of software and privilege allocation. In addition, the VOS itself can run multiple Linux VOS's on itself. The VOS's can only access each other via the network.

VOS's are a technology that IBM has been using since the release of System370 and was present from the 1960's as a research tool. Today it is used in their Z Series Maninframes and this technology has been advanced to the area of the Linux / PC server platforms and it is the continual expansion of PC server VOS applications that will mature this technology in the future.

I like to use and recommend the UML VOS, especially in research environments, hosting services, small offices and home based businesses because it greatly simplifies support and service continuity. Not to mention that it's just cool! Below are some illustrations which will help you understand the differences of the Virtual Technologies in use today and which would be the best choice for your application.

Your normal Hosting Environment (virtual hosting) can be seen as the diagram below:

The virtual host (server software, daemon) applications create multiple domains within a single machine. Virtual hosting only allows the allocation of multiple domains to a single machine. it does not create any virtual computers. In addition, multiple domains can be recognized, but only if the server software has such functions defined along with a combination of network protocols that enable it. Software cannot be installed at the user level. The operating speed is fast and security is not problem if properly managed.

Next you have a Jail & Zones

A single computer can be divided into a plurality of regions within one OS each region to use as if it were the single whole. Installation of software can be done at the user level. Root privileges can also be provided at this level. However, since in the normal OS has not been regionaly divided at the Kernel or system root stage, you are later forcibly introduced to system security problems when your application functions begin to expand. If, perhaps the introduction of such a regional division had been put into place from the beginning as in 'Solaris's Zones', security issues can be resolved. Splitting the user space after the fact results in performance degradation. Most opt for this method first when constructing their application environments.

This leads us to the Virtual OS(VOS)(UML)

In this scenario the VOS system or sometimes referred as a Guest OS runs on top of the Host OS. Multiple VOS's may be run on a single machine. In the case of UML, the VOS is limited to a Linux OS. All features of the the VOS, including also software installation, are available at the user level. Also, it is significantly superior in terms of security. Sometimes, the VOS is a special OS that has been modified to run on the host OS. The speed is fast and limited to Host OS and HW resources.

Finally there's the Virtual Machine(VM).

Like the VOS, Multiple VM's may be run on a single machine. All features of the the VM and the Guest OS, including also software installation, are available at the user level. Security is the same as with the VOS. The difference between the VOS and Virtual Machine is that that VM does not need a special OS that has been modified to run on the Host OS, and does not restrict the type of OS you want to use in the virtual machine. However, in the VM system, the operation is overwhelmingly slow. (Although VMWare by way of tuning uses this approach and is surprisingly fast).

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