Why did 13.10 break my custom keyboard layout?

I was using a custom keyboard layout. Basically I modified the us-mac layout to fit my ideal of a math-heavy version of the regular us layout that also throws German umlauts into mix. It went well and worked marvelously for 6 consecutive versions of Ubuntu. Today's version Upgrade (from 13.04 to 13.10) broke that streak. I now have the usual crappy Macintosh-Layout.

Now xkb just ignores my layout and all of the other changes I make in /usr/share/X11/xkb/symbols/us (tried to switch '0' and '9' everywhere and rebooted - no effect). Why is that?

I suspect I have to do an extra step now for the changes to take effect or something like that. Anyone care to point me in the right direction?

I had the same problem and found sudo dpkg-reconfigure xkb-data will make the changes take effect.

No logout needed if you have enabled multiple layouts; just change the layout once.

I've just found a solution for this problem:

Delete the xkm files in /var/lib/xkb, log out and log in.

Some lines in /var/log/Xorg.0.log indicate that Xorg recompiles and reuses keyboard layouts now:

XKB: generating xkmfile /var/lib/xkb/server-FC37972E27A8F94CD9F5DD859C120B9D933CC5F8.xkm
...
# and on a next restart:
...
XKB: reuse xkmfile /var/lib/xkb/server-FC37972E27A8F94CD9F5DD859C120B9D933CC5F8.xkm