Lessons to be learnt:
1) initramfs is in charge of loading modules, scripts and hooks into the
initrd.img files. These are files containing the kernel.
2) if you get to busybox because your kernel was not loaded, don't panic, you
just probably only need the appropriate modules, scripts and hooks (check How
to solve boot problems with Ubuntu after kernel upgrade:
www.dedoimedo.com/computers/ubuntu-initrd-bug.html).
3) you need to do a chroot environment with the required modules and
decrypting your dm-crypt or LUKS partition
(https://trisquel.info/en/forum/grub-cryptsetup-not-booting-after-kernel-update#comment-40597)
4) just to make sure, purge cryptsetup (aptitude purge cryptsetup
cryptsetup-bin libcryptsetup4) and reinstall (aptitude install cryptsetup
cryptsetup-bin+M libcryptsetup4+M)
5) just to make sure, try installing another kernel or purge and reinstall
the one you have now (I'm not giving instructions for this in case you are a
newbie, and want to take it easy, but if you really dare use aptitude search
'~ilinux' --disable-columns -F '%p' | grep `image\|headers' to see which ones
are installed)
6) use the name for the current unencrypted partition (I used "root" in step
3: cryptsetup luksOpen "$encpart" root) and modify your /etc/crypttab so that
it says something like (le'ts say I used root):
root UUID= none luks
(to get the UUID you can type blkid). You are free to check the man-pages of
crypttab: man crypttab
7) make sure that you have an according entry in /etc/fstab
/dev/mapper/root 0 1
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