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Trying to upgrade to newest Ubuntu from 12.10. The update manager says

failed to download repository information. Check your internet connection

I checked my internet connection(s), and I'm connected both wired and wireless. So I click on the details of the update manager and get the following text:

W:Failed to fetch  404  Not Found
W:Failed to fetch  404  Not Found
E:Some index files failed to download. They have been ignored, or old ones used instead.
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You are using 12.10, but got a PPA for Ubuntu 12.04. Try removing the PPA. – edwin Jul 26 '13 at 4:59
up vote 4 down vote accepted

The error message means Simple light DM manager isn't updated to be used with 12.10.

So it is failing to update the index file thus failing all over.

To correct it do the following,

  1. Uninstall Simple Lightdm manager. sudo apt-get remove simple-lightdm-manager
  2. Remove the repo, sudo add-apt-repository --remove ppa:claudiocn/slm
  3. Now do the update, sudo apt-get update && sudo apt-get upgrade

Repo URL -

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It could happen sometimes. It happened to me last time I upgraded. I think that's a Server Error or something similar. I recommend you to do a backup of all your important data and keep it safe in a USB drive or in the cloud, and then Download the latest Ubuntu ISO and try a CLEAN INSTALL.

The same thing happened to me several times and after that I did the upgrade via Update Manager (Retrying the process for about 5 times) and then the system was so unstable (lots of crashes) so I decided to do what I'm telling you: A clean Install. And it solved the crashes (: Right now I'm a happy user of Lubuntu Raring. (Is the same as UBUNTU but with LXDE instead of UNITY) and it works pretty well.

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