Recently, I faced a error while updating my Ubuntu system.

When I ran “sudo apt-get update”,

it gave me the followinf error message:

 

W: GPG error: http://archive.canonical.com intrepid Release: The following signatures were invalid: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key

 

The way I fixed it was:

 

$ sudo -i

# apt-get clean

# cd /var/lib/apt

# mv lists lists.old

# mkdir -p lists/partial

# apt-get clean

# apt-get update

 

Hope it helps. !!