Phew. The union server upgrade kind-of went to plan. Would have gone more smoothly if I had known the correct default gateway. However, one thing really did mess me up: MySQL.
If you remember just never to use the minus charactor in the name of anything mysqlish, then it's a good little database. But if you do, oh dear. I've filed several bugs about this and the MySQL developers are arguing about how valid the minus sign is, the code certainly has no idea.
mysqldump generally gets quoting correct - except when it comes to the minus charactor at which point CREATE TABLE stops working. Now, when you're importing hundreds of tables you don't see the little error message shoot by with all the status messages (even in `quite' mode). But it turns out that you need to add the --quote-names option to the dump in order for it to do CREATE TABLE correctly. Which is a huge bodge to start off with, because (almost) everything else works fine.
But wait until you get a minus sign in a database name. Now, not only does it not restore the database correctly, it actually errors on the USE statement and goes spewing tables into other databases. And even if you quote the database names, MySQL still can't handle it. At this point I just changed minus to underscore and said bugger it.
Also, openssh 3.7 and onwards can't to PAM support correctly, so I'm sticking to 3.6.1 for now.