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I have installed a fresh copy of Ubuntu Server 12.04 and VirtualBox 4.3. I have set up a VM called "MediaServer" and tried to start it. I then get the following error:

Cannot open host device '/dev/sr0' for readonly access.
Check the permissions of that device ('/bin/ls -l /dev/sr0'):
Most probably you need to be member of the device group.
Make sure that you logout/login after changing the group settings of the current user (VERR_ACCESS_DENIED)

I have looked all over the Internet and have been unable to find a solution. Using Webmin, I tried changing the group settings so that my user name was in the vboxusers group, but that did not work either. I tried various other changes in group settings and none of them worked.

Also, I tried rebooting the server after the changes and that didn't work either.

I have been following a guide on how to set up an Ubuntu server from the website "" and when it came to the section where you could finally set up your first virtual machine, I am stumped. I would really appreciate it if someone could help me.

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Is your user in the group cdrom? – Takkat Nov 3 '13 at 22:30

Your user must be in the cdrom group.

sudo usermod -a -G cdrom $USER

Restart the system and try again.

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