Option   "XkbOptions" "compose:ralt"

Now, I can type most accented characters and umlauts by first hitting the right ALT key.

A few examples (key combinations below all preceded by right ALT key):

• ` e: è (backtick followed by e)
• " u: ü
• , c: ç
• s s: ß

Addendum

Changed this to the Caps Lock key with:

Option   "XkbOptions" "compose:caps"

in xorg.conf

Addendum 2

In Jaunty (and maybe since Intrepid), this no longer works. The update manager comments out the entire keyboard section in xorg.conf, with the comment:

# commented out by update-manager, HAL is now used

A temporary solution is to open a terminal and execute the command:

setxkbmap -option compose:caps

You’ll have to repeat this on each login. You could put this in a shell script and add that to the commands that get executed on startup.

Addendum 3

In Xubuntu Jaunty, you can edit the file /etc/default/console-setup to contain the line:

XKBOPTIONS="compose:caps"

to make this change permanent.

Thanks to foresto on the Ubuntu Forums!

keycode 233 = F20
keycode 234 = F19

After changes, say:

xmodmap ~/.Xmodmap

This activates the keys that I have on the IBM X40 next to the up arrow key on the bottom right of the keyboard. Now, I can bind them to commands Xfce.

Then, I found a nice article on using the CapsLock key to type German umlauts and other special characters.

Basically, just add the following, and you can use CapsLock+u to give ü, and so on for a handful of other characters.

keycode 66 = Mode_switch Multi_key
keycode 117 = Mode_switch Multi_key
keycode 39 = s S ssharp
keycode 38 = a A adiaeresis Adiaeresis
keycode 30 = u U udiaeresis Udiaeresis
keycode 32 = o O odiaeresis Odiaeresis
keycode 14 = 5 percent ssharp  degree
keycode 26 = e E egrave Egrave
keycode 28 = t T EuroSign EuroSign
keycode 27 = r R ecircumflex Ecircumflex
keycode 25 = w W eacute Eacute
keycode 31 = i I idiaeresis Idiaeresis
keycode 21 = equal plus plusminus notsign
keycode 57 = n N ntilde Ntilde
keycode 58 = m M Multi_key
keycode 15 = 6 asciicircum dead_acute  dead_circumflex
keycode 19 = 0 parenright degree masculine
keycode 10 = 1 exclam exclamdown onehalf
keycode 54 = c C ccedilla Ccedilla
keycode 24 = q Q copyright registered

To see all the assigned keycodes:

xmodmap -pke