Mounting dm-crypt device at startup

[hertzsprung]

Ubuntu 10.04.3 Server amd64

I'm having some trouble getting the following configuration to work:

• /dev/sda1 is mounted to /
• I have a key stored in /etc which is used by dm-crypt
• /dev/sdb1 is encrypted. dm-crypt mounts it at /dev/mapper/crypt
• /dev/mapper/crypt is mounted to /crypt

Both mount points are defined in /etc/fstab. When I boot I get the error:

 
The disc drive for /crypt is not ready yet or not present
Continue to wait; or Press S to skip mounting or M for manual recovery

If I understand things correctly, this is because, in upstart, mountall is running before cryptdisk. Really, ubuntu needs to:

1. mount /dev/sda1 to /
2. create /dev/mapper/crypt from /dev/sdb1
3. mount /dev/mapper/crypt to /crypt

Can anyone explain what *should* be happening at boot time? How should I fix this?