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I am using Ubuntu 16.04. The error I get is as follows:

W: http://archive.canonical.com/dists/precise/Release.gpg: Signature by key 630239CC130E1A7FD81A27B140976EAF437D05B5 uses weak digest algorithm (SHA1)
W: The repository 'https://packagecloud.io/computology/apt-backport/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
W: The repository 'http://ppa.launchpad.net/picaso/octave/ubuntu xenial Release' does not have a Release file.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Failed to fetch http://ppa.launchpad.net/picaso/octave/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found [IP: 91.189.95.83 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.

Output of lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 16.04.6 LTS
Release:    16.04
Codename:   xenial

When I try to make changes to Software & Updates, I get this error:

error image

And sometimes the application doesn't even open.

UPDATE: sudo apt-get update runs without errors now but I'm wondering if these updates are enough?

update output

Pablo Bianchi
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BubbleBastard
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    Does this answer your question? [What can I do if a repository/PPA does not have a Release file?](https://askubuntu.com/questions/866901/what-can-i-do-if-a-repository-ppa-does-not-have-a-release-file) – N0rbert Jan 16 '20 at 17:08
  • I tried the answer from the question you linked but it doesn't work for me. I get the output "apt-get update failed for some reason" when I try to purge it. – BubbleBastard Jan 16 '20 at 19:15
  • Welcoem to AskUbuntu! Please [edit] the output of `lsb_release -a` into your question. Thank you for helping us help you! – Elder Geek Jan 17 '20 at 01:29

1 Answers1

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You have to disable the problematic repositories by using Software & Updates (software-properties-gtk).

You need to open Other software tab and then disable the following repositories:

  • http://archive.canonical.com/dists/precise (as your distro is 16.04 LTS that is Xenial Xerus)
  • https://packagecloud.io/computology/apt-backport/ubuntu (even the browser says 404 for this page)
  • http://ppa.launchpad.net/picaso/octave/ubuntu (it does not provide packages for versions after Lucid Lynx 10.04 LTS)

and then confirm reloading package caches.

If issue persists - please run sudo apt-get update manually and add error output to the question. I'm ready to assist you more if any.

N0rbert
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