After installing Virtualbox Guest Addition, we can share folder in our OS into guest Virtualbox. First, we go to shared folder and add new folder to share. Don’t forget to check auto-mount. Start your VM ( which mine is Ubuntu Oneiric 11.10 ) and go to /media to see sf_ubuntu / sf_folder.
When you click on folder, you will get permission denied. Why this happen? It because your user in VM not registered yet in vboxsf group. All you need is add your username into vboxsf group
sudo usermod -G vboxsf -a
Then reboot your VM. Soon as you’re login into VM, you will get full access into shared folder 
Exactly what I am looking for. Thanx…
Perfect, thanks! Saved me a lot of hassle, tears, and stress.
It worked smoothly for me. Thank you very much!
Is the -a option not available in 10.04? I’m trying this on my server and it’s not working. I don’t see it in the man pages either.
Never tried it before.
Doesn’t work for me either in 10.04.1 (latest). It just lists the command line switches as though I typed it wrong — but I see the “-a” and “-G” in there and everything looks correct. It just acts like it doesn’t work. Lame.
Excuse me 12.04.1 (latest) — not 10.04.1.
Figured it out — you have to put your username at the end of the command. So for me I put:
sudo usermod -G vboxsf -a human
YMMV.
Thanks, this was a lifesaver! All of the folder sharing tutorials I found left this valuable part out.
good stuff, need it everytime I add a new vm
Thank’x a lot . It worked perfact.