Authentication error when trying to upgrade from 11.10 to 12.04

Question

I wrote :

~$ do-release-upgrade

and the system says:

  Checking for a new ubuntu release   
   Get:1 Upgrade tool signature [198 B]                                              
   Get:2 Upgrade tool [1551 kB]                                                   
   Fetched 1551 kB in 6s (167 kB/s)                                                
   extracting 'precise.tar.gz'   
   authenticate 'precise.tar.gz' against 'precise.tar.gz.gpg'   
   exception from gpg: GnuPG exited non-zero, with code 2   
   Debug information: 

   gpg: Signature made Thu 11 Oct 2012 07:47:10 AM EET using DSA key ID 437D05B5  
   gpg: can't open `/etc/apt/trusted.gpg'  
   gpg: keydb_search failed: file open error       
   gpg: Can't check signature: public key not found

   Authentication failed   
   Authenticating the upgrade failed. There may be a problem with the network or with the server. 

Please help me!

Answer 1

When trying to do any administrative task like installing an application or upgrading the system, you will always need to have administrative rights. This can be achieved in several ways, 2 of them are:

1. To actually BE the root user (Not recommended. Too much power in your hands. /godmode 1)

2. Prefix any command line with the command sudo.

In your case I recommend doing the second option. And to be sure, do a clean upgrade like this (This way you have less chance to come up with a bug while doing the upgrade, before it or after the upgrade).

sudo apt-get update && sudo apt-get upgrade

After everything is done then execute the following:

sudo apt-get dist-upgrade

This way you can see if the system is ok before doing the version upgrade.

Answer 2

Run these commands:

sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 40976EAF437D05B5
sudo apt-key adv --recv-keys --keyserver keyserver.ubuntu.com 3B4FE6ACC0B21F32

This downloads the missing GPG keys (as mentioned in the original error message) from the Ubuntu GPG keyserver.