QEMU in five minutes

Posted by berto on April 19, 2007

Some friends have been asking me how to use QEMU. While there are many other virtualization packages (such as Virtual Box, KVM or the non-free VMware Player), QEMU has been around for a while, it’s already packaged in Debian stable and it’s really easy to use.

Moreover, the (optional) kernel accelerator kqemu has been released under the GPL a couple of months ago, so it’s a good moment to give QEMU a try.

Let’s see the basic usage:

  • Install QEMU.
    $ apt-get install qemu
  • Create a hard disk image. It’s 2 GB in this example, but don’t worry about the size of the file, it will grow dinamically as you write data to it.
    $ qemu-img create -f qcow hd.img 2G
  • Install things in your new hard disk image. You can boot from a CD-ROM, or an ISO image, a floppy…
    $ qemu -hda hd.img -cdrom /dev/cdrom -boot d
    $ qemu -hda hd.img -cdrom cdimage.iso -boot d
    $ qemu -hda hd.img -fda /dev/fd0 -boot a
    $ qemu -hda hd.img -fda floppy.img -boot a
  • Once the system is installed in your virtual hard disk, you can boot directly from it:
    $ qemu -hda hd.img
  • Or you can forget about hard disks and just use a bootable CD:
    $ qemu -cdrom livecd.iso

And that’s it! QEMU has built-in SMB, TFTP, DNS and DHCP servers. Everything in user space, so you don’t need special permissions nor additional configuration: no kernel modules, no tun/tap interfaces… nothing!. I said it was very easy to use, didn’t I? ;-)

Of course there’s a lot more, but you won’t need it for the basic usage.

If you’re too lazy to install an operating system inside QEMU, you can download a hard disk image built by someone else. Note that QEMU can read the VMware disk format, so you’ve got a really big collection of images ready to work.

And if you want a bit more, you can compile the kqemu kernel accelerator, which will make QEMU run faster.

Now I can remember the old times when I first installed Debian…
Debian bo inside QEMU

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  1. Suso Thu, 19 Apr 2007 10:44:32 CEST

    It’s really good that kqemu has been released as GPL, it’s now a complete opensource solution for virtualizing servers. But I don’t think it’s yet ready for a desktop operating system, because the video card emulation is rather slow. I hope it gets better in the future.

  2. berto Thu, 19 Apr 2007 11:09:50 CEST

    I haven’t made any test with graphic intensive applications but, as you say, I guess that they don’t work well. Éche o que hai

    At least it’s not what I need right now from this kind of software.

    Thanks for your comment, Suso! :)