Rootfs over encrypted lvm

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This howto describes how to setup LVM and rootfs with cryptoLUKS-encrypted drive

Prepare the hard drive and partitions

This is an example partition scheme, you may want to choose differently. /dev/sda1 used as /boot. /dev/sda2 will be encrypted drive with LVM.

/dev/sda1 
/dev/sda2
dd if=/dev/zero of=/dev/sda2 bs=100M 
dd if=/dev/urandom of=/dev/sda2 bs=100M

dd part is optional, only for security reason by overwriting the lingering data on the device with random data. It takes around 6 hours to complete for a 200GB drive.

Note that you will get a message about reaching the end of the device. That's intentional and desired in this case so that this command works without knowing the size of your device.

Encrypting the drive

root # cryptsetup -c aes-xts-plain64 luksFormat /dev/sda2
root # cryptsetup luksOpen /dev/sda2 dmcrypt_root

There you'll be prompted to enter your password phrase for encrypted drive, type your paranoid password there.

Create logical volumes

pvcreate /dev/mapper/dmcrypt_root
vgcreate vg /dev/mapper/dmcrypt_root
lvcreate -L10G -nroot vg           
lvcreate -L2G -nswap vg
lvcreate -L5G -nportage vg
lvcreate -l 100%FREE -nhome vg

Feel free to specify your desired size

Create a filesystem on volumes

mkfs.ext2 /dev/sda1
mkswap /dev/mapper/vg-swap
mkfs.ext4 /dev/mapper/vg-root
mkreiserfs /dev/mapper/vg-portage
mkfs.xfs /dev/mapper/vg-home

Basic system setup

swapon /dev/mapper/vg-swap
mount /dev/mapper/vg-root /mnt/funtoo
mkdir /mnt/funtoo/boot
mount /dev/sda1 /mnt/funtoo/boot

Now perform all the steps required for basic system install, please follow [1] don't forget to emerge next packages:

# emerge cryptsetup lvm2 grub foo-sources

Re-emerge sys-apps/busybox and sys-fs/cryptsetup with the "static" USE flag

Kernel options

Important, do not miss this part. Under General setup --->

[*] Initial RAM filesystem and RAM disk (initramfs/initrd) support

Under Device Drivers --->

Generic Driver Options  --->
   [*] Maintain a devtmpfs filesystem to mount at /dev
[*] Multiple devices driver support  --->
   <*>Device Mapper Support
   <*> Crypt target support

Under Cryptographic API --->

-*-AES cipher algorithms

<*> XTS support (EXPERIMENTAL)


Initramfs setup and configuration

Build your initramfs with better-initramfs project.

   Note

better-initramfs supports neither dynamic modules nor udev, so you should compile your kernel with built-in support for your block devices.

# git clone git@bitbucket.org:piotrkarbowski/better-initramfs.git
# cd better-initramfs
# less README.rst
# bootstrap/bootstrap-all
# make prepare
# make image

Copy resulting initramfs.cpio.gz to /boot.

# cp output/initramfs.cpio.gz /boot

Alternatively pre-compiled binary initramfs available at https://bitbucket.org/piotrkarbowski/better-initramfs/downloads

# wget https://bitbucket.org/piotrkarbowski/better-initramfs/downloads/release-x86_64-v0.7.2.tar.bz2
# tar xf release-x86_64-v0.5.tar.bz2
# cd release*
# gzip initramfs.cpio
# cp initramfs.cpio.gz /boot

Remember, better-initramfs project is a work in progress, so you need to update from time to time. It can be done easily with git. Go to the better-initramfs source dir and follow:

# git pull
# less ChangeLog

Please, read the ChangeLog carefuly and do necessary updates, to /etc/boot.conf, the example config below. Please, backup working initramfs.cpio.gz and /etc/boot.conf before updating initramfs.

Genkernel approach

Funtoo's genkernel capable to create initramfs for encrypted drive. Compile and install kernel and initramfs of your favorite kernel sources:

genkernel --kernel-config=/path/to/your/custom-kernel-config --no-mrproper --makeopts=-j5 --install --lvm --luks all

Configure the bootloader as described above, with correct kernel and initramfs images names. An example for genkernel and grub2:

Template:Code

Grub2 configuration

An example of /etc/boot.conf for better-initramfs Template:Code

Template:Code

Lilo configuration

For oldschool geeks, an example for lilo bootloader. Emerge lilo with device-mapper support

# echo 'sys-boot/lilo device-mapper' >> /etc/portage/package.use/lilo
# emerge lilo

Template:Code

Syslinux bootloader setup

Syslinux is another advanced bootloader which you can find on all live CD's.

# emerge syslinux
# mkdir /boot/extlinux
# extlinux --install /boot/extlinux
# dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/mbr.bin of=/dev/sda
- or -
# sgdisk /dev/sda --attributes=1:set:2
# dd bs=440 conv=notrunc count=1 if=/usr/share/syslinux/gptmbr.bin of=/dev/sda, for GPT partition

Template:Code

Final steps

Umount everything, close encrypted drive and reboot

umount /mnt/funtoo/proc (/dev, /home, /usr/portage, /boot) 
vgchange -a n
cryptsetup luksClose /dev/sda2 dmcrypt_root

After reboot you will get the following:

>>> better-initramfs started. Kernel version 2.6.35-gentoo-r10
>>> Create all the symlinks to /bin/busybox.
>>> Initiating /dev/dir
>>> Getting LVM volumes up (if any)
Reding all physical volumes. This make take awhile...
No volume group found
No volume group found
>>> Opening encrypted partition and mapping to /dev/mapper/dmcrypt_root
Enter passphrase fore /dev/sda2:

Type your password

>>> Again, getting LVM volumes up (if any, after map dmcrypt).
  Reading all physical volumes.  This may take a while...
  Found volume group "vg" using metadata type lvm2
  4 logical volume(s) in volume group "vg" now active
>>> Mounting rootfs to /newroot
>>> Umounting /sys and /proc.
>>> Switching root to /newroot and executing /sbin/init.
INIT: version 2.88 booting
Loading /libexec/rc/console/keymap
  OpenRC 0.6.1 is starting up Funtoo Linux (x86_64)
...boot messages omitted for clarity
   
orion login: oleg
Password:
Last login: Thu Oct 14 20:49:21 EEST 2010 on tty1
oleg@orion ~ %

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