In the basic procedure described in [[Usage]], you need a web browser for the authorization step.  On a headless server without a GUI interface or a web browser, you can get it to work by using a web browser on a separate computer, and pasting the results into the `~/.gdfuse/default/config` (or `~/.gdfuse/label/config` if you use labels) file of your headless server.

Caveat: I do not know whether this is the "optimal" way to do this.  I was in a pinch, and this approach worked.  At first, I had a difficult time getting it to work, but Alessandro responded immediately with help, and we got it to work.   These are the steps I followed, and of course, please edit this page if you have tips or a better approach.   

(I used the "Alternate Authorization Mode"  although the Standard Authorization mode using the GAE (Google App Engine) service may work too.)

1. Install normally as per the [[Installation]] page
1. In the computer with the web browser, create an OAuth2 application and credentials. These steps are similar to those described in the "Alternate Authorization Mode" section in [[Authorization]]. The following steps are what I did, based on my notes:
    1. Sign in to your Google account and create a project: https://console.cloud.google.com/
    1. Click "API Manager" then "Library" in the left-hand pane (will take you to https://console.cloud.google.com/apis/library). Click on "Drive API", then "ENABLE API".
    1. Click "Credentials" in the left hand pane, then click on the button "Create Credentials"
       (OAuth client ID)
        1. Choose "Other"
        1. Choose any product name, e.g "My OCAMLDrive".
        1. Click "Create". You will get a Client ID, a Client Secret.

1. Authorization: Back in your headless server, run `google-drive-ocamlfuse` for the first time. I used labels (in this document, I use the label "me") because I plan on using multiple accounts. However you can also run it without the `-label` parameter and it will use a default name for the label called "default". You will need the Client ID and secret you got from google above.

    From version 0.5.3, you should use the `-headless` option:

          $ google-drive-ocamlfuse -headless -label me -id ##yourClientID##.apps.googleusercontent.com -secret ###yoursecret##### 

    You will get an output like this:

          Please, open the following URL in a web browser: https://accounts.google.com/o/oauth2/auth?client_id=##yourClientID##.apps.googleusercontent.com&redirect_uri=urn%3Aietf%3Awg%3Aoauth%3A2.0%3Aoob&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fdrive&response_type=code&access_type=offline&approval_prompt=force

    Then, you should open the URL above in a graphical web browser, get the verification code from Google
    and put it here:

          Please enter the verification code: 

1. That's it. You should be ready to mount.

        mkdir /my_mnt_dir
        google-drive-ocamlfuse -label me /my_mnt_dir

1. Finally, to unmount, elsewhere in the instructions it says to use `fusermount -u mountpoint`.  That did not work for me for some reason, but `umount mountpoint` did.

Troubleshooting
---------------

When I first tried to mount my drive, I got an error message:


        Cannot retrieve auth tokens.
        Failure("OAuth2 error: invalid_grant (HTTP response code: 400)")


I then ran the same command above, with the addition of the -debug parameter, and still got an error:

		Starting application setup (label=me).
		Opening log file: /root/.gdfuse/me/gdfuse.log
		Cannot retrieve auth tokens.
		Failure("OAuth2 error: invalid_grant (HTTP response code: 400)")

This is where I got stuck but Alessandro helped me right away.  The problem was that my verification code had expired. I don't know what the timeout period is, but I just went back to the google page mentioned above, clicked on "Reset client secret…", which gave me a new secret id and secret, re-ran the auth page to get a new verification code, pasted  the new values into the `config` file, and then it worked like a charm.