Information AboutQemu |
| CATEGORIES ABOUT QEMU | |
| free virtualization software | |
| linux emulation software | |
| mac os x emulation software | |
| powerpc emulators | |
| virtualization software | |
| windows emulation software | |
| x86 emulators | |
QEMU is Free Software written by Fabrice Bellard that implements a fast Processor Emulator , allowing a user to run one operating system within another one. It is similar to projects such as Bochs , VMware Workstation and PearPC , but has several features these lack, including increased speed on x86, and support for multiple architectures in-progress. 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 PCs on a single server. The majority of the program is under the LGPL , with the system mode emulation under the GPL . Fabrice Bellard also wrote a closed source, currently free-of-charge, Linux kernel module (with preliminary ports to FreeBSD and Windows) named ''kqemu'' or ''QEMU Accelerator'', which speeds up i386 emulation on i386 platforms to a level where the loss of speed is negligible even compared to native execution. This is accomplished by running User Mode and Virtual 8086 Mode code directly on the host computer's CPU, and using processor and peripheral emulation only for Kernel Mode (Kernel mode kqemu is in cvs, so this will change soon. But currently it might need some more testing and debugging.) and Real Mode code. This is similar to what VMware Workstation and Virtual PC do. As a result, real mode DOS will not speed up much if at all as a guest OS, whereas Windows 2000 will run at close to native speeds. (Note, however, that as soon as a Memory Manager is used with DOS, most of DOS code is actually run in a virtual 8086 mode task, and should theoretically benefit from kqemu's speedup.) ADVANTAGES OF QEMU
DISADVANTAGES OF QEMU
EXAMPLE OF QEMU'S USAGE This command will create a 500MB hard Disk Image in QEMU's " Qcow " format qemu-img create -f qcow c.img 500M In this command the -f option is for the disk image format. The following formats are supported: raw, qcow, cow, vmdk and and .iso . The following command 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." Note that one could also replace the ''-cdrom linux.iso'' parameter with ''-cdrom /dev/cdrom'' or whatever one's CD-ROM device is, and physically boot from installation medium and install to the image specified after ''-hda'', in this case ''c.img''. qemu -hda c.img -cdrom linux.iso -boot d -m 128 -soundhw sb16 -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 one control the virtual machine (for example, 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. 4]] KQEMU VERSUS QVM86 Fabrice Bellard has stated his willingness to open-source the kqemu QEMU Accelerator module if a company steps up to sponsor it. This has so far not happened, and kqemu remains proprietary. It is free to use, but one is not allowed to distribute it to other people without an explicit authorisation. Distributors wishing to include the QEMU accelerator on CDs, ISO images or packages must contact the author to know the exact terms. Meanwhile, a GPL licensed module purporting to perform the same task, QVM86 has appeared. kqemu has been licensed by Win4Lin for use in their ''Win4Lin Pro Desktop'' product. SEE ALSO
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