Upgrading to 16.04

[Ralf Mardorf]

On Fri, 19 Aug 2016 22:51:01 +0200, Ralf Mardorf wrote:
>IOW it makes typos impossible. The OP could avoid typos by simply
>copying and pasting the commands.

Oops, not really, I copied from the OP :D...

"virtualbox-5.1_5.1.4-110228~Ubuntu~xenial_amd64deb"

so the "." was already missing, but there at least was no typo for
"dpkg" :).

Likely the OP used a browser to download the file, so perhaps

  cd ~/Downloads/
  ls -l

does list the package.