I had an odd need to run an openSUSE 11.2 machine recently, so I installed one under VirtualBox. It worked very well out of the box, with the screen nicely resizing to the VBox window.

However, when I tried to add a shared folder to copy files from the host machine, things started going wrong …

I have a Shared Folder called “hometmp” that shares my ~/tmp directory. Normally this can be easily added to a guest with

$ sudo mount -t vboxsf hometmp ~/tmp

But for some off reason that was failing with a “Protocol error” every time … so I had to do a little digging. It seems that there’s something wrong with the way “mount -t” operates in this case, I’m not interested in openSUSE enough to dig further, but the workaround is to invoke “mount.vboxsf” directly instead. /sbin isn’t on the user path, BTW …

$ sudo /sbin/mount.vboxsf hometmp ~/tmp

And the strangest bit of all — when I went back to my VBox openSUSE to reproduce the error message in order to write this post … the original normal mount option worked just fine!