title: Fatal error after updating to R 3.5.1 on Ubuntu 18.04 Server
body: <p>After updating R to 3.5.1 version on Ubuntu 18.04 Server I got this error message <code>fatal error: unable to open the base package</code>
  I tried to uninstall and reinstall the package three times but I still get the same error. How can I fix this?</p>
  
  <p>This is the current R version on my server>></p>
  
  <pre><code>IN: apt policy r-base
  
  OUT: Installed: 3.5.1-1xenial
    Candidate: 3.5.1-1xenial
    Version table:
   * 3.5.1-1xenial 500
          500 https://cloud.r-project.org/bin/linux/ubuntu xenial-cran35/ Packages
          100 /var/lib/dpkg/status
       3.5.1-1bionic 500
          500 http://ppa.launchpad.net/marutter/rrutter3.5/ubuntu bionic/main amd64 Packages
       3.5.0-1xenial 500
          500 https://cloud.r-project.org/bin/linux/ubuntu xenial-cran35/ Packages
  </code></pre>
  
  <p><strong>Updated</strong></p>
  
  <p>After Trying the steps from @<strong>duckmayr</strong></p>
  
  <p>this's the result of <code>apt policy r-base</code></p>
  
  <pre><code>r-base:
    Installed: (none)
    Candidate: 3.5.1-1bionic
    Version table:
       3.5.1-1bionic 500
          500 http://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ Packages
       3.5.0-1bionic 500
          500 http://cloud.r-project.org/bin/linux/ubuntu bionic-cran35/ Packages
       3.4.4-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.3-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.2-2xenial2 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.2-1xenial1 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.1-2xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.1-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.4.0-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.3.3-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.3.2-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.3.1-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.3.0-2xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.3.0-1xenial0 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
       3.2.5-1xenial 500
          500 http://cran.wustl.edu/bin/linux/ubuntu xenial/ Packages
  </code></pre>
  
  <p>and Get this Error when i Do <code>sudo apt-get install r-base r-base-core</code></p>
  
  <pre><code>    Reading package lists... Done
      Building dependency tree
      Reading state information... Done
      Some packages could not be installed. This may mean that you have
      requested an impossible situation or if you are using the unstable
      distribution that some required packages have not yet been created
      or been moved out of Incoming.
      The following information may help to resolve the situation:
  
      The following packages have unmet dependencies:
   r-base : Depends: r-recommended (= 3.5.1-1bionic) but it is not going to be installed
   r-base-core : Depends: zip but it is not installable
                 Depends: unzip but it is not installable
                 Depends: libpaper-utils but it is not installable
                 Depends: libcurl4 (&gt;= 7.28.0) but it is not installable
                 Depends: libpango-1.0-0 (&gt;= 1.14.0) but it is not installable
                 Depends: libpangocairo-1.0-0 (&gt;= 1.14.0) but it is not installable
                 Depends: libtcl8.6 (&gt;= 8.6.0) but it is not installable
                 Depends: libtiff5 (&gt;= 4.0.3) but it is not going to be installed
                 Depends: libtk8.6 (&gt;= 8.6.0) but it is not installable
                 Recommends: r-recommended but it is not going to be installed
                 Recommends: r-base-dev but it is not going to be installed
  E: Unable to correct problems, you have held broken packages.
  </code></pre>
  
  <p>and Get this when trying <code>sudo apt install libcurl4-gnutls-dev libxml2-dev libssl-dev</code></p>
  
  <pre><code> Reading package lists... Done
  Building dependency tree
  Reading state information... Done
  libcurl4-gnutls-dev is already the newest version (7.58.0-2ubuntu3.3).
  Some packages could not be installed. This may mean that you have
  requested an impossible situation or if you are using the unstable
  distribution that some required packages have not yet been created
  or been moved out of Incoming.
  The following information may help to resolve the situation:
  
  The following packages have unmet dependencies:
   libssl-dev : Depends: libssl1.0.0 (= 1.0.2g-1ubuntu4.13) but 1.0.2n-1ubuntu5.1 is to be installed
                Recommends: libssl-doc but it is not going to be installed
   libxml2-dev : Depends: libxml2 (= 2.9.3+dfsg1-1ubuntu0.6) but 2.9.4+dfsg1-6.1ubuntu1.2 is to be installed
  E: Unable to correct problems, you have held broken packages.
  </code></pre>