Qemu revisited
I mentioned Qemu a short while back. I’ve used it in the past for testing linux livecds. After doing the writeup though I was encouraged to look at it again and see if/how much it’s improved since I last got an update. Wow….
For starters, I spent a bit of hairpulling but got the kqemu module working this time. kqemu is an accelerator module that interfaces directly with the kernel. It’s purported that qemu without the accelerator is 5-10x slower than the host machine, WITH the accelerator it’s in the ballpark of 1-2x slower. Not bad. I did try it and am impressed with the acceleration.
My test install was Windows 98 second edition. I installed to a 1 GB hard drive image and must say it performed as well as my old copy of Win4lin. I haven’t tried anything too fancy, but I did attempt starting qemu with the -user-net option which gave me easy seamless access to the internet from within the qemu OS. Very nice. I also tried it out with several other images (mostly cds) that I’ve collected.
One interesting feature of qemu is the ability to boot an existing disc or drive. For instance, you have an old dos boot floppy in your 3.5 inch drive, you can use qemu to boot from it, or your cdrom, or a hard drive. Obviously you want to be cautious about this on the primary drive, ( -snapshot is a handy switch), but it’s possible to do things which I would have otherwise thought were just impossible.
As I’ve said there is a windows version out now, although it’s in testing. It can really save you a lot of rebooting especially if you’re into testing or developing livecds. There is also a site called Free OS zoo, which provides some images for download of freely available (and distributable) operating systems. So you’ll find several linux variants there, some bsd variations and one darwin install (that I ran into some problems trying to untar.) These images will essentially save you from creating your own image and booting qemu up with “install media” and building it yourself. I think the free os zoo is an idea that REALLY could be expanded.
I didn’t get to play around with much more advanced networking because I discovered a strange problem with the tun driver on my desktop workstation. I’ll have to sort that out before I can get anything fancier than -user-net going.