title: Postgresql 9.5 installation - Config owner (postgres:105) and data owner (ubuntu:1000) do not match, and config owner is not root
body: <p>When installing <code>postgres9.5</code> on <code>ubuntu 14.04</code>, the following command stops at an error:
      $sudo apt-get install postgresql-9.5 pgadmin3</p>
  
  <p>Here is the error message:</p>
  
  <pre><code> Preparing to unpack .../postgresql-9.5_9.5.4-1.pgdg14.04+2_amd64.deb ...
   * Stopping PostgreSQL 9.5 database server                                       * Error: Config owner (postgres:105) and data owner (ubuntu:1000) do not match, and config owner is not root
                                                                           [fail]
  invoke-rc.d: initscript postgresql, action "stop" failed.
  dpkg: warning: subprocess old pre-removal script returned error exit status 1
  dpkg: trying script from the new package instead ...
   * Stopping PostgreSQL 9.5 database server                                       * Error: Config owner (postgres:105) and data owner (ubuntu:1000) do not match, and config owner is not root
                                                                           [fail]
  invoke-rc.d: initscript postgresql, action "stop" failed.
  dpkg: error processing archive /var/cache/apt/archives/postgresql-9.5_9.5.4-1.pgdg14.04+2_amd64.deb (--unpack):
   subprocess new pre-removal script returned error exit status 1
  Errors were encountered while processing:
   /var/cache/apt/archives/postgresql-9.5_9.5.4-1.pgdg14.04+2_amd64.deb
  E: Sub-process /usr/bin/dpkg returned an error code (1)
  </code></pre>
  
  <p>What causes the error? </p>