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QEMU is free software which implements a fast processor emulator written by Fabrice Bellard which allows you to run one operating system within another. t is similar to projects such as Bochs and PearPC, but has several features these lack, including increased speed and support for multiple architectures. By using dynamic translation it achieves a reasonable speed while being easy to port on new host CPUs. QEMU has two operating modes:
- User mode emulation, QEMU can launch Linux processes compiled for one CPU on another CPU. Linux system calls are converted because of endianness and 32/64 bit mismatches. WINE and Dosemu are the main targets for QEMU.
- System mode emulation, QEMU emulates a full system, including a processor and various peripherials. It enables easier testing and debugging of system code. It can also be used to provide virtual hosting of several virtual PC on a single server.
Advantages of QEMU
- supports both IA-32 (x86) and PowerPC architectures
- support for other architectures in both host and emulated systems (see homepage for complete list)
- increased speed - some applications can run in close to real time
- support for running Linux binaries for other platforms
- can save and restore the state of the machine (programs running, etc.)
- virtual network card emulation
Disadvantages of QEMU
- Incomplete support for Microsoft Windows and other host operating systems (emulation of these systems is just fine)
- Incomplete support for less frequently-used architectures
- Still not as fast as a virtual machine such as VMWare
- Requires X11 and SDL
- More difficult to install and use than comparable emulators
Example of QEMU's usage
This command will create a 500MB hard disk image in QEMU's "qcow" format.
qemu-image create -f qcow c.img 500MB
This will start a virtual machine with 128MB of memory, using the c.img file created with the previous command and booting from a CD-ROM image linux.iso. The virtual machine will have audio support and use the system's clock to run in "real time."
qemu -hda c.img -cdrom linux.iso -boot d -m 128 -enable-audio -localtime
This will create a virtual machine with 64MB of memory, booting from c.img and using the system's CD-ROM drive. The virtual machine will run in full-screen mode.
qemu -hda c.img -cdrom /dev/cdrom -boot c -m 64 -full-screen
While a virtual machine is running, press Ctrl-Alt-2 to access the "QEMU console," which lets you control the virtual machine (eg, changing disk images, rebooting, quitting QEMU, etc.) and Ctrl-Alt-1 to switch back to your emulation. Ctrl-Alt-F toggles between full-screen and windowed mode.
External Links
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