If I install a bare-metal hypervisor (say, ESXi), would it allow me to run Windows 7 concurrently with Linux?
Would it allow me to run multiple instances of Windows 7?
When I'm sitting at the PC that's running Win7 and Linux on a hypervisor, which OS do I see when I look at the screen? (I'm suspecting that the only way to access either OS is to do a remote login.)
Assuming the answer to #2 is yes, how do you manage multiple installs of Win7 on the same hard drive?
Thanks in advance!
If you simply want to run Linux and Windows in parallel you may of course do this on e.g. ESXi. Still, the OSes would run with virtualized (or emulated) hardware available to them, i.e. you would not be able to easily access all the hardware directly and the hypervisor itself not only introduces an overhead but this overhead is not deterministic.
If you want to run an RTOS (like Real-Time Linux) or any other RTOS, then you need a "real-time hypervisor".
You can google for such hypervisors - there are a few out there.
(I dont want to recommend one here as we are a vendor of such a solution our selves)
Regards
GFL
Related
Xen is a Type I hypervisor that means it can run directly on hardware so why do we need to install Ubuntu or CentOS or any OS to run Xen? It should run directly on the hardware as it's a Type I hypervisor.
The reason that an OS is needed is because Xen itself does not directly provide any mechanism for creating/managing virtual machines. Because these tasks require things like creating disk images, editing configuration files, setting up networking etc. It would be wasteful for the Xen project to reimplement all of this functionality when it is already included in widely-used OSes like Linux.
The only way to interact with Xen is by making hypercalls, some of which can only be made from the dom0 (Domain 0) VM. As noted in the Xen wiki this means that the hypervisor can be left to just the tasks which only it can perform - checking page tables, allocating resources for new domains, and scheduling domains.
I'm not aware of any type 1 hypervisor which does not need an OS in one way or another - many of them use Xen under the hood, with a custom OS. Things like VMWare ESXi (which does not use Xen) bundle their own OS as part of the distribution so still have an OS running on top of the hypervisor to provide needed functionality.
I'm using a program that is calculating things as it receives information and I need it to be running on multiple virtual machines on my PC at the same time.
Now before I was going to set this up, I was wondering which operating system would be ideal to be running on the virtual machines to run as many of them as possible on restricted ressources? The only requirement is that my program is not able to run on Linux.
I was thinking of going back to Windows XP on each virtual machine, assuming the newer operating systems are taking too much ressources for themselves, but that's just a guess.
Hope someone has more knowledge than me about this and can help me out.
Thank you!
If you are NEVER going to take these VMs online XP is a better choice. Windows 8.1 (as well as 10) is a recent design and hence is designed for high powered modern hardware, XP was designed long ago for old slower hardware. Running an older OS on newer hardware will allow it to compartively quick, certainly much faster than a new OS on old hardware. Another matter is what programs you will run, if it is old programs they will be compatible with XP, if it is new ones there is a chance XP will not be able to run them. If you are going to take these VMs online then XP is a bad idea, wonderful an operating system as it was it is now becoming insecure due microsoft stopping producing updates to patch holes in it, And do not forget also that Microsoft wouldn't support XP anymore (http://windows.microsoft.com/en-us/windows/end-support-help), so you should go back to the drawing table and fix your priorities and needs and then decide , cheers !
If you cannot run *NIX / BSD Systems you can use WFL windows xp for legacy computers it works on 128 mb RAM
Update: i386 old systems.
The questions I would like to ask are:
1) What exactly does hypervisor do? Why is it needed?
2) What is the difference between hypervisor and Java Virtual mMchine?
3) Does JVM use a hypervisor?
4) When a host operating system like linux can handle multiple guest operating system,why use hypervisor?
Would be great help if someone shed light on this
A Hypervisor also known as hardware virtualization are a virtualization layer that allows running one or more native operating system on top of it, as if they run on a physical machine. It is similar to emulation but only runs operating systems that would be able to run without the Hyperviser, which are much faster.
Both are virtualization layers. However Java are optimized for performance and portability. While Java are technicaly an emulator, it are much faster than an hyperviser. This can be achieved because the emulated platform are designed for fast emulation. Java do not run x86 or x86_64/amd64 code, it runs something called Bytecode. The technical term for Bytecode are Intermediate Language (IL). It are compiled to code that are native to your processor when you run it, by the Just In Time compiler (JIT). As the JIT do a compilation process it can make sure that the program follows Java:s security constraints, by simply not generating code that violates such constraints. The Hyperviser enforce security constraints by intercepting so called privileged instructions and by emulating devices such as disk drives. This are done because native x86 or x86_64/amd64 code are very hard for a program to understand, and changing it so that it self-enforce security constraints are next to impossible. Java on the other hand runs Bytecode which are easy for a program to understand and chance so that it self-enforce security rules.
The short answer: An hyperviser are slower than Java but allows you to run a multitude of complete operating systems, and all the software available for them. This while Java are faster, but you can only run Java software on it. If you want to run Windows and Office in your virtual machine, you can't do that in Java.
I think I answered this above but no, it use code inspection and modifies the program so that it self-enforce security rules. This can be done because runnable Java application are in a intermediate state called Bytecode, which are easy for Java to understand, inspect, find code that may violate the rules and modify it in order to obey them. This are a rather complex process that have several advantage over hypervisor. The first advantage are "compile once run everywhere", as Java are compiled and distributed as bytecode. The second advantage are speed, JIT:ed code have the same speed as non-virtualized code even when strict security are enforced. The disadvantage are that only Bytecode programs can run, so you for example cannot run Windows or Linux inside the virtual machine.
If you are running another operating system like Windows or another Linux distribution - you are running an Hyperviser. KVM, Xen and VirtualBox are examples of Hypervisors. You can also run multiple instances of Linux with one shared kernel, known as OS-based virtualization or "Container". But a Container share the kernel and therefor you can only virtual machines with the OS you are running. The advantage with Containers it are more lightweight as you do not need to run multiple kernels on top of each other...
Hypervisor or virtual machine manager, is a program that allows multiple operating systems to share a single hardware host.
JVM or Java Virtual Machine interprets bytecode for a computers processor so that it can perform Java program instructions.
No JVM does not use hypervisor as it is not an virtual machine that runs an OS rather it is just a interpreter.
A host operating system manages different VMs using Hypervisor or virtual machine manager
Before answering your questions, I would recommend you search related entries in wikipedia. A hypervisor is used to run multiple guest OSes while JVM is used to interpret java byte code. JVM runs on top of OS and it doesn't care whether the OS runs on top of bare metal or on a hypervisor. Actually, linux can handle multiple guest operating systems with KVM which is part of the linux kernel. So the description of the last question is totally wrong.
I'm trying to understand if Xen can fit my needs:
I need to have a Windows 7 image that I can copy to different machines (with different hardware) to have kind of default installation for every new entry in the office and faster replacement.
Is that possible to use the hypervisor for this?
Is that possible to use network boot as well of the hypervisor not to install Xen on every machine?
Edit: Will I be able tu use multiple displays?
Thanks.
It is possible if and only if you have installed Xen on every machine on your network that is not a good idea. Xen and other type-1 hypervisors are usually used to multiplex a high-end server into a set of virtual machines. Xen is also known for its para-virtualization technique which is not applicable for Windows.
Have you ever thought of VDI (Virtual Desktop Infrastructure) solutions? It enables you to have all your operating systems on a single machine and transfer the desktop to the clients.
Where can virtualization techniques be applied by an application developer? How can virtualization be applied on a day-to-day basis?
I would like to understand from veteran developers making use of it. I am interested in the following things:
How it helps in development.
How it could be used for testing purposes.
What are the recommended practices.
The main benefit, in my view, is that in a single machine, you can test an application in:
Different OSs, in case your app is multiplatform
Different configurations, like testing a client in one machine and a server in the other, or trying different parameters
Diffferent performance characteristics, like with minimal CPU and RAM, and with multicore and high amounts of RAM
Additionally, you can provide VM images to distribute applications preconfigured, be it for testing or for running applications in virtualized environments, where it makes sense (for apps which do not demand much power)
Can't say I'm a veteran developer, but I've used virtualization extensively when environments need to be controlled. That goes for:
Development: not only is it really useful to have VMs about for different deployment environments (e.g. browser versions, Windows XP / Vista / 7) but especially for maintenance it's handy to have a VM with the right development tools configured for a particular job.
Testing: this is where VMs really shine: it's great to have different deployment environments that can be set back to a known good configuration and multiple server instances running in parallel to test load balancing.
I've also found it useful to have a standard test image available that I can run locally to verify that a fix works. If it doesn't then I can roll back to the previous snapshot with no problems.
I've been using Virtual PC running Windows XP to test products I'm developing. I have clients who still need XP support while my primary dev environment is Vista (haven't had time to jump to Win7 yet), so having a virtual setup for XP is a big time saver.
Before each client drop, I build and test on my Vista dev machine then fire up VPC with XP, drag the binaries to the XP guest OS (enabled by installing Virtual PC additions on the guest OS) and run my tests there. I use the Undo disk feature of Virtual PC so I can always start with a clean XP image. This process would have been really cumbersome without virtualization.
I can now dump my old PCs at the local PC Recycle with no regrets :)
Some sort of test environment: if you are debugging malware (either writing it or developing a pill against it) it is not clever to use the real OS. The only possible disadvantage is that the viruses can detect that they are being run in the virtualization. :( One of the possibilities to do it is because the VM engines can emulate a finite set of hardware.