Qemu what is it

QEMU can also be used purely for CPU emulation for user-level processes, allowing applications compiled for one architecture to be run on another. However, the default is to use DirectSound. QEMU has multiple operating modes: [2].

QEMU can run without a host kernel driver and yet gives acceptable performance. It uses dynamic translation to native code for reasonable speed, with support for self-modifying code and precise exceptions. QEMU can save and restore the state of the virtual machine with all programs running. Guest operating-systems do not need patching in order to run inside QEMU. The virtual machine can interface with many types of physical host hardware.

USB devices can be completely emulated mass storage from image files, input devices , or the host's USB devices can be used however, this requires administrator privileges and does not work with all devices. Virtual disk images can be stored in a special format qcow or qcow2 that only take up disk space that the guest OS actually uses.

This way, an emulated GB disk may occupy only a few hundred megabytes on the host. The QCOW2 format also allows the creation of overlay images that record the difference from another unmodified base image file.

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Close Welcome back! You've successfully signed in. Close Nearly there! This is typically the case in classical virtualization environment VMware, VirtualBox, … when a user wants to run Windows on Linux for instance. The terminology is usually Host and Guest target.

Nowadays, QEMU offers virtualization through different accelerators. Virtualization is considered an accelerator because it prevents unneeded emulation of instructions when host and target share the same architecture. But the host operating system must allow QEMU to take benefit of them. You can take benefit of the speed of x86 hardware virtualization under the three major operating systems.

Notice that the TCG is also considered an accelerator. We can enter a long debate about terminology here …. Reading the source code still remains your best option.