If you are getting this message while you are trying to run a command that needs administrative rights, then your user probably is not allowed to use the sudo command!
The solution is simple. First of all, keep a backup of file /etc/sudoers. Then,
Either you run the visudo command with administrative rights to edit the sudoers file and append an extra line to the file, like this:
user_name ALL=(ALL) ALL
or use the echo command:
echo “user_name ALL=(ALL) ALL” >> /etc/sudoers