Installing tex on ubuntu 18.04 over the internet

Removing texlive:

sudo apt-get purge texlive-*
sudo apt-get autoremove
sudo apt-get autoclean

According to tug (https://www.tug.org/texlive/quickinstall.html):

First, just to be sure, 

rm -rf /usr/local/texlive/2018
rm -rf ~/.texlive2018

Then, download the installer (a Perl script) from here:

https://www.tug.org/texlive/acquire-netinstall.html

Then extract, move to the extracted directory, and run the installer.