Rootfs over encrypted lvm

From Funtoo
Revision as of 00:13, 19 February 2014 by Duncan.Britton (Talk)

Jump to: navigation, search

This howto describes how to setup LVM and rootfs with cryptoLUKS-encrypted drive. It is not meant to be a standalone installation guide, rather, it is meant to be read alongside the Funtoo Linux Installation Guide.

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 -- /boot partition.
  • /dev/sda2 -- BIOS boot partition (not needed for MBR - only needed if you are using GPT) This step required for GRUB2. For more info, see: [1] for more information on GPT and MBR.
  • /dev/sda3 -- / partition, will be the drive with LUKS and LVM.

Wipe the hard drive

Warning: This action will destroy all data on the disk.
# gdisk /dev/sda

Command: x ↵
Expert command: z ↵
About to wipe out GPT on /dev/sda. Proceed?: y ↵
GPT data structures destroyed! You may now partition the disk using fdisk or other utilities.
Blank out MBR?: y ↵

Note Note: You will get a message about reaching the end of the device when the dd command has finished. This behavior is intended.

Encrypting the drive

Read more about different cipher options here: [2]

# cryptsetup --cipher aes-xts-plain64 luksFormat /dev/sda3
# cryptsetup luksOpen /dev/sda3 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 --name root vg           
# lvcreate -L2G --name swap vg
# lvcreate -L5G --name portage vg
# lvcreate -l 100%FREE -nhome vg

Feel free to specify your desired size by altering the numbers after the -L flag. For example, to make your portage dataset 20GB's, use the flag -L20G instead of -L5G.

Create a filesystem on volumes

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

Basic system setup

# swapon /dev/mapper/vg-swap
# mkdir /mnt/funtoo
# mount /dev/mapper/vg-root /mnt/funtoo
# mkdir -p /mnt/funtoo/{boot,usr/portage,home}
# mount /dev/sda1 /mnt/funtoo/boot
# mount /dev/mapper/vg-portage /mnt/funtoo/usr/portage
# mount /dev/mapper/vg-home /mnt/funtoo/home

Now perform all the steps required for basic system install, please follow [3] don't forget to emerge the following before your install is finished:

  • cryptsetup
  • lvm2
  • a bootloader (grub recommended)
  • kernel sources

Editing the fstab

Fire up your favorite text editor to edit /etc/fstab. You want to put the following in the file:


# <fs>                  <mountpoint>  <type>    <opts>                          <dump/pass>
/dev/sda1               /boot         ext2      noauto,noatime                  1 2
/dev/mapper/vg-swap     none          swap      sw                              0 0
/dev/mapper/vg-root     /             ext4      noatime,nodiratime,defaults     0 1
/dev/sr0                /mnt/cdrom    auto      noauto,ro                       0 0
/dev/mapper/vg-portage  /usr/portage  ext4      noatime,nodiratime              0 0
/dev/mapper/vg-home     /home         ext4      noatime,nodiratime              0 0

Kernel options

Note Note: This part is particularly important: pay close attention.








Initramfs setup and configuration

Better-initramfs

Build your initramfs with better-initramfs project.

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

# cd /opt
# git clone git://github.com/slashbeast/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, a pre-compiled binary initramfs is 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:

# cd /opt/better-initramfs
# git pull
# less ChangeLog

Note Note: Please read the ChangeLog carefuly and perform necessary updates to /etc/boot.conf. Also, please backup the working /boot/initramfs.cpio.gz and /etc/boot.conf before updating better-initramfs.

Genkernel

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 

Bootloader Configuration

Grub2 configuration

better-initramfs

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

boot {
  generate grub
  default "Funtoo Linux"
  timeout 3
}
"Funtoo Linux" {
  kernel vmlinuz[-v]
  initrd /initramfs.cpio.gz
  params += enc_root=/dev/sda3 lvm luks root=/dev/mapper/vg-root  rootfstype=ext4 resume=swap:/dev/mapper/vg-swap quiet

Now, run boot-update to write the configuration files to /boot/grub/grub.cfg

genkernel

Configure the bootloader as described above, with correct kernel and initramfs images names. An example for genkernel and grub2. You will be editing /etc/boot.conf:

boot {
  generate grub
  default "Funtoo Linux"
  timeout 3
}
"Funtoo Linux" {
  kernel kernel-genkernel-x86_64-3.13.0
  initrd initramfs-genkernel-x86_64-3.13.0
  params += crypt_root=/dev/sda3 dolvm real_root=/dev/mapper/vg-root  rootfstype=ext4 resume=swap:/dev/mapper/vg-swap quiet

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

Example /etc/lilo.conf:

append="init=/linuxrc dolvm crypt_root=/dev/sda2 real_root=/dev/mapper/vg-root"
boot=/dev/sda
compact
default=funtoo
lba32
prompt
read-only
timeout=50
image=/boot/kernel-genkernel-x86_64-3.13.0
initrd=/boot/initramfs-genkernel-x86_64-3.13.0
label=funtoo

Syslinux bootloader setup

Syslinux is another advanced bootloader which you can find on all live CD's. Syslinux bootloader does not require additional BIOS boot partition. /dev/sda2 is the root partition.

# 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

Example /boot/extlinux/extlinux.conf:

LABEL kernel1_bzImage-3.2.1
MENU LABEL Funtoo Linux bzImage-3.2.1
LINUX /bzImage-3.2.1
INITRD /initramfs.cpio.gz
APPEND rootfstype=ext4 luks enc_root=/dev/sda2 lvm root=/dev/mapper/vg-root

Final steps

Umount everything, close encrypted drive and reboot

# umount -l -v /mnt/funtoo/{dev, proc, 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 ~ %

Additional links and information