I am using ubuntu 12.04(LTS) 64 bit. i have edited "group" file in directory /etc. i added my user name which is "erfan" in front of "vboxusers" as following :
in below you can see some lines of my group file
root:x:0: daemon:x:1: bin:x:2: . . . erfan:x:1000: sambashare:x:124: debian-xfs:x:125: vboxusers:x:126:erfan vboxsf:x:127: guest-59wkHG:x:128:
after this change i can not use "sudo" command and i receive following message:
"erfan is not in the sudoers file. This incident will be reported."
i can not install any package and manage my operating system.
i think if i can find a way to delet my user name ("erfan") in front of "vboxusers", then this problem will resolve.
could you give me an idea to delet it and edit "group" file? or any way to resolve this problem?