You do not need root access to run a program at startup.
1/. Login under your user account, create a text file with gedit and add:
#!/bin/sh
xterm -hold -e "cd /home// && ./xmr-stak --"
2/. Save the file as xmr-stak_Launch.sh in the root of your home directory.
3/. Open terminal and make the script executable by your user:
chmod +x /home//xmr-stak_Launch.sh
4/. Open the Ubuntu Dash, search for "Startup Applications" and click on it.
5/. In the "Add Startup Application" window add:
Name: XMR-STAK
Command: Browse to the xmr-stak_Launch.sh file in the root of your home directory and click 'Add'
XMR-STAK should now launch after your login to Ubuntu. If you want to add a delay before starting the application, open the starutp file located in:
~/.conf/autostart/XMR-STAK.sh.desktop
with gedit and add a delay to the file:
[Desktop Entry]
Type=Application
Exec=/home//xmr-stak_Launch.sh
Hidden=false
NoDisplay=false
X-GNOME-Autostart-enabled=true
X-GNOME-Autostart-Delay=
Name[en_US]=XMR-STAK
Name=XMR-STAK
Comment[en_US]=
Comment=