How do I recover from boot error when my root is on RAID and LVM?

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http://serverfault.com – I run an Archlinux server and it has happened to me three times now that I did a pacman -Syu, forgot about it and then a powerfailure happened and my box wouldn't boot anymore. (yes I know I'm not a very thoughtful sysadmin) Ofcourse I had forgotten to run mkinitcpio or some other configuration that pacman did not resolve automatically. Since I made the mistake of having my root partition on both RAID and LVM the recovery process is a bit more complex, so how to do it? edit: I have the answer to my question but I have to wait 7 hours to post it. (HowTos)