I need help solving upgrade problem, "fetching upgrade failed," 12.04 to 12.10

I am using xfce4 on an Acer c70 Chromebook. I managed to successfully update my system to 14.04 about a month ago using update manager, but was left with many unresolved bugs that I could not work around. So, defeated, I decided to reset everything and do a fresh install.
On attempting to update 12.04 to 12.10, I get errors in both update manager and terminal indicating a "failure to fetch" due to network problems. I have gone through an exhaustive list of help pages trying to solve this problem, but thus far either none are pertinent to my specific problem or i am unable to understand how to accomplish the steps involved.

I am able to apt-get update, and apt-get upgrade, but do-release-upgrade yields the following:

Checking for a new Ubuntu release
Err Upgrade tool signature                                                       
  404  Not Found [IP: 91.189.91.14 80]                                           
Err Upgrade tool                                                                 
  404  Not Found [IP: 91.189.91.14 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.

Solution 1:

I got the same problem 3 days ago and you have two options (considering your network connection is fine).

First option is go HERE choose your country etc. and mark your version of Ubuntu as 14.04. Then paste generated list into /etc/apt/sources.list (better backup first). Then run sudo apt-get update; sudo apt-get upgrade -y then run do-release-upgrade. It's highly possible that you also have to repair grub after that. And to do that you will need bootable CD or USB, so you simply can run your update from Live CD. And that is the second option.

Solution 2:

You should set source.list to EOL repositories as described here: End of Life Upgrades

i.e. to something like

http://old-releases.ubuntu.com/ubuntu/ CODENAME main restricted universe multiverse

maybe you need additionally change value of "Notify me of a new Ubuntu version" from "For long-term support version" to "For any new version". After that "Software updater" allow you to upgrade to next available version.

Solution 3:

I got similar error and this is how I resolved it .

root@ub-lab:~# do-release-upgrade
Checking for a new Ubuntu release
Get:1 Upgrade tool signature [198 B]
Err Upgrade tool
  Connection failed [IP: 91.189.88.152 80]
Fetched 198 B in 0s (0 B/s)
WARNING:root:file 'xenial.tar.gz' missing
Failed to fetch
Fetching the upgrade failed. There may be a network problem.

This will help only if you have network problem and you are not able to download the root file

search for the error message and mark the file which is missing. In my case its xenial.tar.gz

Then open the file /var/lib/update-manager/meta-release-lts and you will see the url where the file xenial.tar.gz is located.

In my case its archive.ubuntu.com/ubuntu/dists/xenial-updates/main/dist-upgrader-all/current/xenial.tar.gz

So download the file with other internet option, where you don't have any restrictions and put this file on server

I placed it in /tmp/xenial.tar.gz and now update the url in /var/lib/update-manager/meta-release-lts for file xenial.tar.gz and point it to local.

in my case its file: /tmp/xenial.tar.gz

That's it. Then run:

do-release upgrade

It starts working and takes file from local file system and continues the upgrade.

Solution 4:

It might be enough to just purge and reinstall update manager. It worked for me, having the exact same error message. See here.