Saturday May 23, 2009

VirtualBox USB Ports

Running CentOS as my host OS and using VirtualBox to run "everything else", it didn't take long before I was running into USB problems. In my case I had a Windows 2000 guest on a CentOS 5 host (same for RedHat EL) and I wanted to use ActiveSync to connect to my WM5 Windows Mobile device.

I'm diverting for a sec, but this is the big reason why I like VirtualBox so much. I do software development for the Windows Mobile platform (http://www.locatea.net/) which requires a lot of software installation for Visual Studio and then even more for the various Windows Mobile SDKs. It is quite a job to get it all installed correctly. Previously that whole install could (and would) easily be screwed up because some completely unrelated application would mess up the registry, forcing you to reinstall the server and start from scratch.

Now, by virtualizing my desktop, I have an instance that I solely use for Windows Mobile software development. If I need Microsoft Office I do it in another Windows guest. And if I want to tryout a new software package that I don't really trust, I simply clone my base image and install it in there. If the app doesn't work out or behaves badly, I can simply blow the whole image.

So, where many people think that desktop virtualization is just great for running different types of OSes on a single host, IMHO it is even more important because it allows you to create multiple environments, that have very dissimilar functionality, but can have the same platform requirements. Of course I also use it to run OpenSolaris on my Mac. :-)

Back to USB in Windows guests. Out of the box it doesn't work, at least not on my platform. A little googling provides a lot of recommendations to add an entry to /etc/fstab (none /proc/bus/usb usbfs devgid=501,devmode=0664 0 0). It seems that for Ubuntu this fixes the problem, but not for RedHat / CentOS. It took me a lot of searching, but finally I found in an obscure corner of some forum a solution. You have to modify your /etc/rc.d/rc/sysinit file.

if [ ! -d /proc/bus/usb ]; then
        modprobe usbcore >/dev/null 2>&1 && mount -n -t usbfs \
                        /proc/bus/usb /proc/bus/usb -o devgid=501,devmode=664
        mount -n -t usbfs /proc/bus/usb /proc/bus/usb -o devgid=501,devmode=664

This piece is mainly already there, but you need to add the "-o" parameters. In here "501" is the GID you have specified in your /etc/group for the vboxusers group.

After having done this, the Windows guest recognizes USB sticks, external hard drives and nicely connects to my mobile phone.