Sorry, user "user" is not allowed to execute '/usr/bin/apt-get update' as root on

Question

I've installed Debian 7 and just executed sudo apt-get update and got this error:

Sorry, user xsma is not allowed to execute '/usr/bin/apt-get update' as root on ACS.ACS

my user is "xsma" and "ACS" is the name of the computer.

Answer 1

I just solved this by reading Debian sudo page with two steps:
1) add the user to be sudo to the sudo group.
2) log out and log back in to gain that group's permissions.

Debian page said use: # adduser xsma sudo, while I had used # vigr and # vigr -s.