First, obtain the qBittorrent source code. Either download and extract a .tar archive from Sourceforge or clone this git repo (git clone https://github.com/qbittorrent/qBittorrent).
Enter the folder in a new terminal window and run:
./configure --prefix=/usr --disable-gui make
Note1: If you're using libtorrent-rasterbar from the 0.16.x series, you also need to pass the "--with-libtorrent-rasterbar0.16" option to configure. qBittorrent v3.3.x has dropped the support of libtorrent 0.16.x.
Note2: If you want to compile with qt4 instead of qt5, you also need to pass the "--with-qt4" option to configure.
Note3: If you want to disable ALL authentification on the WebGUI, change some lines as explained here: https://github.com/qbittorrent/qBittorrent/wiki/Disable-authentification-of-webGUI/
And finally to install qBittorrent:
sudo make install
That's it! qBittorrent-nox should now be installed. You can now run qBittorrent-nox using the following command:
Since you disabled the graphical user interface, qBittorrent can only be controlled via its Web UI. If you haven' t disabled authentification, as a default, you can access it from:
http://localhost:8080 Username: admin Password: adminadmin
A documentation about running qBittorrent without GUI is available here.