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Having some problems! Every time I try perform the update from 12.04 to 14.04 I am met with the following error:

kev@masterpc:~$ sudo do-release-upgrade
Checking for a new Ubuntu release
Err Upgrade tool signature                                                     
  404  Not Found [IP: 80]                                         
Err Upgrade tool                                                               
  404  Not Found [IP: 80]                                         
Fetched 0 B in 0s (0 B/s)                                                      
WARNING:root:file 'quantal.tar.gz.gpg' missing
Failed to fetch
Fetching the upgrade failed. There may be a network problem. 

In the software centre under software sources I have used both servers (Australian & Main server) but to no avail. My network also appears to be fine!

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Have also just realised that the update manager is telling the latest update is to 12.10 NOT to 14.04? Here is my current version info kev@masterpc:~$ lsb_release -a LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-‌​amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noar‌​ch Distributor ID: Ubuntu Description: Ubuntu 12.04.5 LTS Release: 12.04 Codename: precise – Bubba Aug 10 '14 at 9:25
Possible duplicate of…, also see – TheSchwa Aug 10 '14 at 9:31
As far as I know, 12.04 LTS is not EOL? – Bubba Aug 10 '14 at 9:43
That's the kinda weird thing about it. You're right, 12.04 isn't EOL because it's an LTS, but 12.10 is EOL, and in general you have to upgrade one release at a time (12.04 > 12.10 > 13.04 > ... , not 12.04 > 14.04), hence the problem. – TheSchwa Aug 10 '14 at 9:44
And it is not possible to do an LTS to LTS upgrade via update centre? – Bubba Aug 10 '14 at 9:46

Figured it out!

In the software centre -> Software sources under the updates tab you must change "Notify me of a new Ubuntu version:" set to "For long term support versions" then in a terminal run

sudo apt-get update
sudo do-release-upgrade -d

Running the update command seems to be critical, so don't forget it!

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