Dosbox -writeconf

When I try to make a file in dosbox to keep all my config settings so I dont have to type them in all the time it says "illegal command:

First I start off with gnomesu dosbox.
Then -writeconf /home/… where I want the file to be(within Dosbox).

Then is says illegal command. I then tried touch dosbox.conf. And that said the same thing.

Can anyone help me please?