GNOME and GDM

GNOME Overview

GNOME is a desktop environment which runs on top of X Windows. It is a free software effort and is included in most modern Linux releases, including those supported by the Computer Systems Lab. More information can be found on the GNOME website.

GDM Overview

GDM is the GNOME Display Manager. It handles your login session by performing the following tasks:

1. Username and password authentication
2. Login session selection (GNOME session/System session/failsafe session)
3. Language customization (only for applications with GNOME internationalization features enabled)

Available Login Sessions

There are currently 3 on CSL-supported computers:

1. GNOME session: the GNOME desktop is started at login.
2. System session: your ~/.xsession file is exec'ed; applications and window managers specified there are run at login.
3. Failsafe session: you get a regular xterm and nothing else. This is good if your login environment needs repair

Default Login Session

New users after June 14, 2006 will run the GNOME desktop by default. Accounts existing prior to that date will default to a System session. All users can change this during the login process (see below).

Changing the Login Session

While the GDM username and password entry boxes are present, there will be a Session menu at the bottom of your screen. This is where you change your login session type. If you select something different than your default session type, you will be prompted to decide whether to make your selection the new default or not.

An example of what the login screen looks like and the location of the Session menu:

Login Session Configuration File

It is stored in your ~/.dmrc file. If this file is damaged or removed, the GDM login manager will default to a GNOME desktop login session.

Customizing Your GNOME Session

We provide some information for customizing your GNOME login session. More complex customizations may require consulting GNOME online documentation at http://library.gnome.org/users/user-guide/stable/

How to run applications automaticly at login

1. You will need to run the Gnome Session Properties application in the System -> Preferences -> More Preferences -> Sessions menu. You can also run gnome-session-properties from a shell prompt (provided you are logged in on an X display).
2. Select the Startup Programs tab
3. Add the applications you want to run at login time

How to customize the application bar in you GNOME session

Just right-click on the menu bar, whether that be across the top or bottom of your desktop...you can right-click it to unlock and move it as you like. Once you right-click on the menu bar, you will be given the open to Add to Panel. From there, you can choose an Application Launcher to choose one of the applications in the Applications menu, or you can select Custom Application Launcher to be prompted for a command line argument, icon to use, etc. to define your own application name and location.

Changing window focus parameters

This is handled under System -> Preferences -> Windows. Check or uncheck the box to move focus as the mouse moves over the window.

Adding additional application menu application entries

Entries for programs go in ~/.local/share/applications; you will need to create this directory (and its parent directories) if it does not exist. You can copy an existing menu entry from /usr/share/applications as a starting point--they end with a .desktop extension--then rename and edit as appropriate, or you can create your own .desktop file for your application if you know the syntax.

Note the Categories field in the .desktop file available for you to classify which submenu, if any, this program entry appears in. You may want to change it to or add MyApps to this list if want this application to appear in a personal submenu detailed in the next section.

You can also specify the name that appears in the applications menu and an icon (if desired) to display with the entry. Any application menu entries with category fields set to values not caught by existing submenus will display at the bottom of the application menu.

Adding additional application menu submenus

1. You'll need to create a menu definition for the new submenu in ~/.config/menus. You can find other menu definitions in files in /etc/xdg/menus. Your entry will look something like this:

<!DOCTYPE Menu PUBLIC "-//freedesktop//DTD Menu 1.0//EN"
"http://www.freedesktop.org/standards/menu-spec/1.0/menu.dtd">



<Menu>
  <Menu>
    <Name>My Apps</Name>
    <!-- Menu items to include in the toplevel -->
    <Include>
      <And>
        <Category>MyApps</Category>
      </And>
    </Include>
  </Menu>
</Menu>

2. Then add an entry to ~/.config/menus/applications.menu like this:

  <MergeFile><path_to_your_home_directory>/.config/menus/apps.menu</MergeFile>

NOTE: New submenus will NOT appear in your application menu until you have an application defined to appear in that submenu. See the above instructions for adding application entries to do this.

How do I test such modifications?

We suggest you login using the Failsafe Session when making such tweaks to your gnome desktop. You can run gnome-session there to see if your modifications worked as expected. Just do a standard gnome logout to get back to the xterm window for further modifications or fixes.

I can't login with GNOME without seeing some errors pop up!

The GNOME desktop software is far from perfect. If you run into errors when you login, try the following first and see if it clears up your login problem:

1. Logout
2. Ctrl - Alt - F1 to get a virtual terminal
3. Login with the virtual terminal
4. Remove or rename directories /tmp/*-username (if your login name was john, you would want to remove or rename /tmp/*-john
5. Logout
6. Alt - F7 (or, in some rare cases, Alt - F8)
7. Login using the gdm login panel

If you are still having trouble logging in without errors popping up, report those errors to lab@cs.wisc.edu

-- JohnPerkins - 13 Jun 2006