Since last post many things have changed. No more NetBSD on my laptop (this has to do with several things, I’ll write about in a future post): I had to fall in love with Gentoo! I’ll try to give you some quick overview related to this posts title: Encryption under Gentoo using Luks.

There are serveral (good!) tutorials out there. Among these I’ve used:

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  There you'll get a lot of information related to the topic. I've basically followed the same steps as described in the HowTo. However I didn't get any functionable system at all. Especially the initramfs part seems to be buggy. Therefore: Follow the steps ín the article <strong>except</strong> the initramfs part!
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  Really good explanations. If you want some technical background to this whole thing, this is the place to be.
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  Another nice howto I've found.
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  As already mentioned above, you'll get into troubles if you don't have a working initramfs. Follow this link to get detailed information how to create your own - as I did! - initramfs and how to adapt it to your needs.
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http://en.gentoo-wiki.com/wiki/DM-Crypt_with_LUKS
http://de.gentoo-wiki.com/wiki/DM-Crypt (german)
http://djamc.ath.cx/2008/01/20/howto-gentoo-vollverschlusselung-mit-cryptsetup-und-initramfs-bei-der-installation/ (german)
http://en.gentoo-wiki.com/wiki/Initramfs

There is no need for additional explanations! Just follow the instructions in the tutorial and you’re done.

My initramfs

Here is my initramfs structure I’m using:

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$ tree
.
├── bin
│   ├── busybox
│   ├── gpg
│   └── gpg-error
├── dev
├── etc
├── init
├── lib
│   └── modules
├── mnt
│   └── root
├── new-root
├── proc
├── README
├── root
│   └── keys
├── sbin
│   ├── cryptsetup
│   └── mdev
├── sys
└── usr
    └── bin

15 directories, 7 files

Make sure all binaries are statically linked. And this is my init script:

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$ cat init 
#!/bin/busybox sh

# Some useful functions
rescue_shell() {
    echo "Something went wrong. Dropping you to a shell."
    busybox --install -s
    exec /bin/busybox sh
}

# GPG workaround
cp -a /dev/console /dev/tty

# Mount the /proc and /sys filesystems.
mount -t proc none /proc
mount -t sysfs none /sys

busybox --install -s
mdev -s 
echo /bin/mdev > /proc/sys/kernel/hotplug

# Decrypt root
while [ ! -e /root/keys/sda1_key ] ; do
   sleep 2
   echo "> Decrypt root ..."
   gpg -o /root/keys/sda1_key -d /root/keys/sda1_key.gpg 2> /dev/null
done

# Unlock partition
cryptsetup -d /root/keys/sda1_key luksOpen /dev/sda1 root

# Mount new root 
mount /dev/mapper/root /new-root

# Create swap device
cryptsetup -c twofish -h sha256 -d /dev/urandom create swap /dev/sda6
mkswap /dev/mapper/swap

# Unmount old root
umount -l /proc
umount -l /sys

# Start new system
exec switch_root /new-root /sbin/init || rescue_shell

Don’t forget to copy your keys to */root/keys/ *and rename them properly. Afterwards all you have to do is to create the initramfs file:

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$ cd /usr/src/initramfs
$ find . -print0 | cpio --null -ov --format=newc | gzip -9 > /boot/initramfs.cpio.gz

That’s all!