Ubuntu 12.04 apt-get update GPG error

Question

my goal is upgrading Ubuntu 12.04 LTS to 14.04 LTS. I don't have running a surface, because it's only used as a issue tracking server. At first i wanted to update the current system.

After sudo apt-get update i get this:

OK   http://archive.canonical.com precise Release.gpg
OK   http://archive.canonical.com precise Release
Hole:1 http://archive.ubuntu.com precise Release.gpg [198 B]
OK   http://archive.canonical.com precise/partner Sources
OK   http://archive.canonical.com precise/partner amd64 Packages
Hole:2 http://archive.ubuntu.com precise-updates Release.gpg [198 B]
OK   http://archive.canonical.com precise/partner i386 Packages
Ign http://archive.canonical.com precise/partner TranslationIndex
Hole:3 http://archive.ubuntu.com precise-security Release.gpg [198 B]
OK   http://archive.ubuntu.com precise Release
Ign http://archive.ubuntu.com precise Release
Hole:4 http://archive.ubuntu.com precise-updates Release [49,6 kB]
Ign http://archive.ubuntu.com precise-updates Release
Hole:5 http://archive.ubuntu.com precise-security Release [49,6 kB]
Ign http://archive.ubuntu.com precise-security Release
W: GPG-Fehler: http://archive.ubuntu.com precise Release: Die folgenden Signaturen waren ungültig: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
W: GPG-Fehler: http://archive.ubuntu.com precise-updates Release: Die folgenden Signaturen waren ungültig: BADSIG 40976EAF437D05B5 Ubuntu Archive Automatic Signing Key <ftpmaster@ubuntu.com>
E: GPG-Fehler: http://archive.ubuntu.com precise-security Release: Die folgenden Signaturen waren ungültig: NODATA 2

After that i tried

sudo rm /var/lib/apt/lists/* -vf
sudo apt-get update && sudo apt-get upgrade

because i thought the error results in a wrong entry in my sources.list, but the course didn't change.

Then i tried to get the key with

gpg --keyserver keyserver.ubuntu.com --recv 40976EAF437D05B5

which resulted in

gpg: requesting key 437D05B5 from hkp server keyserver.ubuntu.com
gpgkeys: key 40976EAF437D05B5 not found on keyserver
gpg: no valid OpenPGP data found.
gpg: Total number processed: 0

At this point i don't know what to do anymore, hoping for your help!

Greetings, vach

Answer 1

Solved this problem by:

• Visit keyserver.ubuntu.com

• Search for the missing key:

0x40976EAF437D05B5

(note the 0x before the key)

• Click on the link on the pub section and copy the whole content beginning with

-----BEGIN

and save this content into a new file "key"

• Add this key manually: sudo apt-key add key (followed by an OK response)

• Updating again sudo apt-get update works fine