title: Cannot perform apt update CLOSED
body: <p>I just installed Lubuntu 19.04 on a computer, everything went correct. But 3 days after that, the <code>apt update</code> command stopped working. I do not know what could be the causant of that.
  This is my output running <code>apt update</code>:</p>
  
  <pre><code>Ign:1 http://archive.ubuntu.com/ubuntu disco InRelease
  Ign:2 http://security.ubuntu.com/ubuntu disco-security InRelease
  Ign:3 http://archive.ubuntu.com/ubuntu disco-updates InRelease
  Err:4 http://security.ubuntu.com/ubuntu disco-security Release
    404  Not Found [IP: 91.189.88.152 80]
  Ign:5 http://archive.ubuntu.com/ubuntu disco-backports InRelease
  Err:6 http://archive.ubuntu.com/ubuntu disco Release
    404  Not Found [IP: 91.189.88.142 80]
  Err:7 http://archive.ubuntu.com/ubuntu disco-updates Release
    404  Not Found [IP: 91.189.88.142 80]
  Err:8 http://archive.ubuntu.com/ubuntu disco-backports Release
    404  Not Found [IP: 91.189.88.142 80]
  Reading package lists... Done
  E: The repository 'http://security.ubuntu.com/ubuntu disco-security Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://archive.ubuntu.com/ubuntu disco Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://archive.ubuntu.com/ubuntu disco-updates Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  E: The repository 'http://archive.ubuntu.com/ubuntu disco-backports Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  </code></pre>
  
  <p>And this is my <code>sources.list</code> file.</p>
  
  <pre><code># See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
  # newer versions of the distribution.
  deb http://archive.ubuntu.com/ubuntu/ disco main restricted
  # deb-src http://archive.ubuntu.com/ubuntu/ disco main restricted
  
  ## Major bug fix updates produced after the final release of the
  ## distribution.
  deb http://archive.ubuntu.com/ubuntu/ disco-updates main restricted
  # deb-src http://archive.ubuntu.com/ubuntu/ disco-updates main restricted
  
  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
  ## team. Also, please note that software in universe WILL NOT receive any
  ## review or updates from the Ubuntu security team.
  deb http://archive.ubuntu.com/ubuntu/ disco universe
  # deb-src http://archive.ubuntu.com/ubuntu/ disco universe
  deb http://archive.ubuntu.com/ubuntu/ disco-updates universe
  # deb-src http://archive.ubuntu.com/ubuntu/ disco-updates universe
  
  ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
  ## team, and may not be under a free licence. Please satisfy yourself as to
  ## your rights to use the software. Also, please note that software in
  ## multiverse WILL NOT receive any review or updates from the Ubuntu
  ## security team.
  deb http://archive.ubuntu.com/ubuntu/ disco multiverse
  # deb-src http://archive.ubuntu.com/ubuntu/ disco multiverse
  deb http://archive.ubuntu.com/ubuntu/ disco-updates multiverse
  # deb-src http://archive.ubuntu.com/ubuntu/ disco-updates multiverse
  
  ## N.B. software from this repository may not have been tested as
  ## extensively as that contained in the main release, although it includes
  ## newer versions of some applications which may provide useful features.
  ## Also, please note that software in backports WILL NOT receive any review
  ## or updates from the Ubuntu security team.
  deb http://archive.ubuntu.com/ubuntu/ disco-backports main restricted universe multiverse
  # deb-src http://archive.ubuntu.com/ubuntu/ disco-backports main restricted universe multiverse
  
  ## Uncomment the following two lines to add software from Canonical's
  ## 'partner' repository.
  ## This software is not part of Ubuntu, but is offered by Canonical and the
  ## respective vendors as a service to Ubuntu users.
  # deb http://archive.canonical.com/ubuntu disco partner
  # deb-src http://archive.canonical.com/ubuntu disco partner
  
  deb http://security.ubuntu.com/ubuntu/ disco-security main restricted
  # deb-src http://security.ubuntu.com/ubuntu/ disco-security main restricted
  deb http://security.ubuntu.com/ubuntu/ disco-security universe
  # deb-src http://security.ubuntu.com/ubuntu/ disco-security universe
  deb http://security.ubuntu.com/ubuntu/ disco-security multiverse
  # deb-src http://security.ubuntu.com/ubuntu/ disco-security multiverse
  </code></pre>
  
  <p>Can anyone say me how can i fix that? 
  Obviously, I cannot install anything:</p>
  
  <pre><code>apt install apache2
  Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  E: Unable to locate package apache2
  </code></pre>
  
  <p>Thanks.</p>