Below is the XKB file that I use on my keyboard in order to type German characters. The Right-Alt key is overridden and used for typing the characters. RAlt-a produces ä, RAlt-e produces €, RAlt-s produces ß, RAlt-u produces ü, RAlt-o produces ö.
Most of the other keys are also used to print extended characters.. you'll just have to experiment, as they're defined in the latin keymap.
However, we override a few keys here to make dead keys, which allow things like accents. RAlt-' then "a" by itself produces "á", RAlt-` then "a" produces "à". You can probably figure out what does what by reading the mappings below directly.
I load this with <kbd>setxkbmap us_de</kbd>, but you could also add an entry in /etc/X11/xkb/rules/xorg.xml (or xfree86.xml) and then select it from the GNOME keyboard configurator.
// This file is located at /etc/X11/xkb/symbols/pc/us_de
//
// It works on RHEL4.. Ubuntu requires that you place it in symbols/ and
// change the include path below.
partial default alphanumeric_keys
xkb_symbols "basic" {
include "pc/latin"
name[Group1]="en_US";
name[Group2]="de_DE";
key { [ 2, at, twosuperior, oneeighth ] };
key { [ 3, numbersign, threesuperior, sterling ] };
key { [ 4, dollar, onequarter, currency ] };
key { [ e, E, EuroSign, EuroSign ] };
// ydiaeresis is for .nl
key { [ y, Y, ydiaeresis, yen ] };
key { [ u, U, udiaeresis, Udiaeresis ] };
key { [ o, O, odiaeresis, Odiaeresis ] };
key { [ a, A, adiaeresis, Adiaeresis ] };
key { [ s, S, ssharp ] };
key { [ slash, question, questiondown, dead_hook ] };
key { [ apostrophe, quotedbl, dead_acute, dead_diaeresis ] };
key { [ 1, exclam, exclamdown, exclamdown ] };
key { [ n, N, ntilde, Ntilde ] };
key { [ slash, question, questiondown, questiondown ] };
key { [ grave, asciitilde, dead_grave, dead_tilde ] };
key { [ 0, parenright, dead_abovering ] };
key { [ minus, underscore, dead_macron ] };
key { [ comma, less, dead_cedilla, dead_ogonek ] };
key { [ 6, asciicircum, dead_circumflex, dead_caron ] };
key { [ 9, parenleft, dead_breve ] };
key { [ 0, parenright ] };
key { [ equal, plus, dead_doubleacute ] };
include "level3(ralt_switch_multikey)"
};
If you're not in a position to modify the system files, you can also use an xmodmap file, such as the following:
keycode 0x1A = e E EuroSign currency keycode 0x1E = u U udiaeresis Udiaeresis keycode 0x20 = o O odiaeresis Odiaeresis keycode 0x26 = a A adiaeresis Adiaeresis keycode 0x27 = s S ssharp section ! right alt keycode 0x71 = Mode_switch
Save that as .xmodmap (or whatever), and load it with <tt>xmodmap .xmodmap</tt>