Speaking of virtual machines, everyone is familiar with. You need to use a virtual machine scenes are very much like those who want to write the operating system comrades often need a virtual machine to run and debug his writing system; another example, like the study of network architecture of friends, you need on your computer N virtual out a variety of network system components. (This configuration requires the computer is strong enough for the job, but fortunately enough for my computer.) Also, for example with Windows, Linux want to play, want to play with Linux Windows, this virtual machine play is also more convenient; for example, someone wants to look at the last currently the most popular ah big data, cloud computing, ah, want to try Hadoop, Spark, OpenStack something, no virtual machine how to build a test environment. I also often use a virtual machine in Windows is used in VMWare, feel it is powerful, easy to use, efficiency is very high. My blog has a lot of content is to toss out in a virtual machine, you can share out of it? In the Linux system, I also use a virtual machine. For example, this one in my "Using GCC and GNU Binutils write 16-bit code in real mode x86 can run," I will use QEMU FreeDOS to run a system, I used to debug 16-bit code. In fact, I am also a favorite operating system of primary research, get to know QEMU is from the "write their own operating system," the book begins.
Classification virtual machine is complex. What full virtualization, paravirtualization what made people dizzy. I used a lot of the virtual machine, always hard to tell these concepts. And desktop users and enterprise user expectations for the virtual machine is not the same. For example, I might expect such a virtual machine:
1. It can simulate a complete PC, I can give it to install any operating system I want to install;
2. It must be relatively easy to use graphical interface, but also can simulate the computer running Windows or Gnome accessibility of such graphics system, play the game the best;
Hard is the host operating system in an image file 3. The operating system used by the customer, ready to copy and paste, ready to be packed away;
4. best to simulate some hardware itself does not exist, such as multiple network cards or something.
Obviously, VMWare Workstation is a desktop user can perfectly meet the requirements of my most satisfying virtual machine. I often use it to toss the various Linux distributions, and running smoothly. Of course, in the open-source Linux world we are going to use such a thing should not be cracked version. But do not worry, Linux rivers and lakes, as well as VirtualBox, QEMU such a virtual machine software available.
While enterprise users do, they expect the virtual machine might look like this:
1. It does not have to be able to simulate a complete computer, with emphasis on CPU, memory, disk and network cards, the focus is when the server can use;
2. It is certainly better than the performance of the virtual CPU performance must be close to the physical CPU, be sure to take advantage of all the features of the physical CPU, for performance, and even can be installed only after the modified operating system kernel; (so-called paravirtualization. )
3. It is certainly better than isolation, its purpose is to put a machine into a machine with N, N and manage virtual machine host confidential the less resource-intensive as possible, the client is the master, the host is the time; (such as Xen.)
4. As enterprise customers on the performance of the pursuit, so the client may use the hard disk is really a separate physical hard disk, disk arrays, network file system or something, not just an image file on the host;
5. It does not necessarily need to have a graphical interface, since the use of the command line interface easier to manage, such as automation, ah, remoting, ah, ah, what the mass;
6. For more enterprise-class high availability requirements, such as what hot backup ah, ah, what the dynamic migration.
These expectations can be seen from the above, the virtual machine deep water areas, the market outlook is relatively bright. Each virtual machine manufacturers to hype their products that is very common, because each user's desired point can make a big fuss thing. The so-called Pro-Yuan Xian fish, as retreat webs, various virtual machines fun to see again, not as his own try.
Today I introduce the QEMU. Or the old rules, my blog is not a manual to use the software, so it's learning materials QEMU also refer to the official website:
Alternatively, enter the following command in your system:
and many more...
QEMU itself is a very powerful virtual machine, even in Xen, KVM virtual machines QEMU products are ultimately figure. In official documents QEMU also mentioned, QEMU can use Xen, KVM and other technologies to accelerate. Why do we need to accelerate it, it is because if you want a QEMU when its own simulates a complete PC, it inside the CPU ah what are simulated, it can even simulate different CPU architectures, for example, simulated using Intel X86 CPU of a computer or computer MIPS ARM computer, so simulate the running speed of the CPU'd never make physical CPU. After using an accelerated, it can be the guest operating system CPU instruction forwarded directly to the physical CPU, natural increase operating efficiency.
QEMU is also a very simple virtual machine, giving it a hard disk image you can start a virtual machine, if you want to customize the configuration of the virtual machine, such as what kind of CPU use ah, what kind of card ah, what kind of network configuration ah, specify the appropriate command line parameters on it. It supports many disk image formats, including VirtualBox disk image file is created. It also provides a disk image creation and management tool for qemu-img. QEMU and command-line parameters used tool, you can directly view the documents.
My computer is an Intel CPU, and I think also a virtual PC, so naturally I installed qemu-system-x86, is another useful qemu-utils. See QEMU package of tools and documentation
Use qemu-img create a disk image file, use the qemu-system-i386 start the virtual machine and install an operating system
WinXP estimated to be currently the best on the entire network to download the operating system. After running the above command to bring up the familiar system installation interface. The installation process I do not long-winded. The figure is the effect of installing the WinXP operating system later. Can give qemu-system-i386 specify more parameters, start again WinXP, I except a 2G memory allocated to it, and I also use it as a parameter -smp 2 allocated two CPU, also use -vga vmware and designated as VMWare virtual graphics card for it. While specifying two CPU, but the performance is still poor. Just drag the window about CPU usage soared to 100%.
Virtual machine CPU, although shown as 3.5GHz, but it is clear that QEMU analog out, and there are significant differences in the physical CPU. In fact my computer configuration is quite powerful, Core i7-4770K quad-core eight thread CPU, see the output lshw
Intel Core i7-4770K CPU, the virtual XP also allocated out of the 2G memory and two CPU, but fluency is still poor. Description only using QEMU desktop users still can not meet our needs.