Say you want to use the keyboard both as an english and as a french one. You do not want to log out and select a different language but quickly switch between them.<br />
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This is how you do it on any linux machine with x11 or x.org:<br />
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Edit your config file, something like <code>/etc/X11/xorg.conf</code>. Find the keyboard section and add to the end of it:<br />
<pre>    Option &quot;XkbRules&quot;   &quot;xorg&quot;
    Option &quot;XkbLayout&quot;  &quot;us,ru,ro,fr&quot;
    Option &quot;XKbOptions&quot; &quot;grp:alt_shift_toggle&quot;</pre><br />
The two letter country codes you can guess. The above shows us english, russian, romanian and french. I don't know where to find a list.<br />
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The second option tells it you want to use the Alt+Shift key combination to switch the input locale. Again, I don't know what else you can put into there. Being a former windows guy alt+shift is good enough for me :)<br />
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Each window manager or desktop environment comes with it's own applet that will show you the currently selected language and let you switch it with a mouse click.<br />
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Enjoy.