Keep the system clipboard and the primary selection synchronized
xclip
$ make install
Note that the installation is not as root, so it will only affect the current user. It pre-suposes that the paths $HOME/.local/systemd/user and $HOME/.config/bin exist and will install there the necessary service file and the script.
The only thing that is running is the clipsync.sh script. This should be copied into your path and invoked in the background to keep synchronizing your clipboards.
If you have systemd installed then you can enable clipsync as a user service after having installed it with make install by running.
$ systemctl --user enable clipsync.service
$ systemctl --user start clipsync.service
These instructions work on arch linux, I'm not sure how they would port to other distributions