disable the cdrom in Ubuntu 11.10 OS
Solution 1:
From: Managing Ubuntu Linux Users and Groups
To remove a user [eg. john] from membership of a group [eg. accounts] use:
sudo deluser john accounts
And, to undo:
sudo adduser john accounts
So to match example (in other answer):
sudo deluser tachyons cdrom
sudo adduser tachyons cdrom [to undo]
Solution 2:
Do it in your risk
Take a backup of /etc/group
press ctrl+alt+t and type gksudo gedit /etc/group
Remove the users from cdrom(in this screenshot tachyons is the user name)
save the file and restart your pc