virtualbox.org

I run Ubuntu guest on FreeBSD host (I know it's not supported but it works fine)

My question is that I am getting 'Protocol error' when I try to read the folder in guest.
It mounts without an error.

What might be the problem?

Protocol error with which application? Gedit? Nautilus? Terminal?

Any application. For example 'ls' prints:
ls: cannot open directory host-yuri/: Protocol error

Then something really is not right there. Are you sharing a private folder from the Host like your My Documents or profile folder?

I am sharing my home directory.
It's not private. Its name on the host is /home/yuri, and I am trying to mount it in the guest as /home/yuri/host-yuri

And that's the problem. you can't share your entire home folder. You have to pick a subfolder.

This was it. Thanks!

I have a suggestion: VirtualBox GUI should warn users if they select home directory or any other directory not allowed to be shared. This will save a lot of time for many people in the future.
Or maybe just allow sharing the home directory. This should be no big deal on UNIX systems.

And that's the problem too. For some, it gives errors like yours, for others, like me, it just works without any issue. I have shared my home folder with an XP VM and it's mapped without problems. I can read and write on it. I also have my /home shared with an Ubuntu VM, no issues either. It's a though problem to fix.
For now, avoid sharing personal folders.