Updates are not working

Question

Updates in my system are not getting installed..

sudo apt-get install is giving the following error:-

W: GPG error: http://archive.cloudera.com precise-cdh4 Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 327574EE02A818DD

Update Manager is showing different error as shown in ScreenShot

Answer 1

Open a terminal and add the missing key with bellow command

sudo apt-key adv --recv-key --keyserver keyserver.ubuntu.com 327574EE02A818DD

Then run

sudo apt-get update