Recommended virtualization technique for debugging/developing FreeBSD

Bill Moran wmoran at
Tue Feb 26 18:46:11 UTC 2008

In response to Peter Schuller <peter.schuller at>:

> Hello,
> I was wondering what people use, in the abscense of suitable actual hardware, 
> to debug/develop FreeBSD (the kernel in particular). I'm willing to resort to 
> almost any host, including Windows, as long as I have something reliable.
> I haven't had much luck with qemu (crashes), nor virtualbox (crashes). I was 
> going to go for vmware on Windows, but while it ran FreeBSD pretty well, 
> before I had even percolated the disk layout enough to trigger the bug 
> (required root-on-zfs) I was hoping to trigger, the vmware configuration tool 
> crapped out on me and produced a configuration it could not itself read.
> What do all you regular kernel developers use, if not physical hardware?

I know that bochs was used during some of the initial development of
the amd64 port, because bochs can emulate amd64 on i386 hardware.

You're not going to see anything like impressive performance with bochs,
but it will allow you to see _everything_ the kernel is doing, i.e., you
can track each CPU instruction if you so desire.

Bill Moran

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