Unable to update ubuntu 12.04.5 to latest version

Question

I'm new to Ubuntu, trying to update Ubuntu 12.04.5 LTS to latest version and unable to do it.

Error:

$ sudo do-release-upgrade -d 
Checking for a new Ubuntu release No new release found 

Answer 1

Personally never had a problem running:

sudo apt-get update
sudo apt-get dist-upgrade

and then reboot.

Answer 2

Begin by finding an up-to-date mirror near you from this list.

Select the mirror you've chosen by selecting it from Software & Updates Ubuntu software tab as described here

Issue the sudo do-release-upgrade command.

This commadn has a number of switches that modify it's actions that you can review with the command man do-release-upgrade

the -d switch as shown in your post indicates:

Check if upgrading to the latest devel release is possible

Another option is the -p switch which indicates:

Try upgrading to the latest release using the upgrader from Ubuntu-proposed

My preferred method of upgrading is often referred to as the clean install Which includes backing up my home directory (I use a seperate partition for home to make this simple) and Installing fresh the version I want over or alongside if space is available my existing installation.