Or, you know, you could use a terminal to start it. Just cd( the command to 'change directory') to the directory where your binary is:cd ~/df_linux
Then you need to run your excutable which is, by default, named df:
./df
That works pretty fast, especially if you're using the tab key to autocomplete file directories for you.
You could even set up a script in '/usr/bin' to start it just by typing 'dorf' or something into the terminal(df is already taken.) Bash searches '/usr/bin/' and a few other folders to see if there's anything relevant to anything you enter into the terminal. You will need root permissions to do anything in '/usr/bin' so 'sudo' and, subsequently, your password will be used. Just cd to '/usr/bin':
cd /usr/bin
And make a new file there with sudo(I like vim but most people will be using nano.):
sudo nano dorf
Then, in the file, type the directory path of your file with 'cd', and the command to run df:
cd /home/azrathud/df_linux; ./df
Now you will need to close and save the file and then change the permissions of the file so it can be executed like this:
sudo chmod +x dorf
Close the terminal and open a new one. Viola! You can open df by typing 4 characters. Mapping the terminal to a shortcut also makes it faster.(I do this for minecraft and LCS too)
I don't know about unity(I'm sticking with an older version of Ubuntu until the annoying sound problems cease to persist.) But I imagine you could type:
cd /home/{username}/df_linux;./df
into a file with the extension '.sh' like 'dorf.sh' which means it's for the shell(the terminal) and then drag it into unity.
edit:editing /usr/bin with chmod requires permissions