Installing Debian or Devuan GNU+Linux with full disk encryption (including /boot)

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This guide is written for the Debian distribution, but it should also work for Devuan with the net installer. Other Debian based GNU+Linux distributions may also work, using these instructions.

If booting in legacy VGA textmode

Text mode is when you start in a low resolution text console. In Libreboot, you can tell because there will be no background graphic in the GRUB menu and the text will look like it has been upscaled from a lower resolution.

To boot the Debian net installer, make sure to specify fb=false on the linux kernel parameters in GRUB. This will boot the installer in text mode instead of using a framebuffer. By default, the netinstaller will try to switch to a high resolution framebuffer. Due to lack of INT10H video BIOS services and mode switching support in Libreboot (for video), this will fail.

Libreboot starts in either text mode or VESA framebuffer mode. When you boot a Linux kernel, on any supported Libreboot target, the Linux kernel video driver for your hardware is handling everything on its own without help from BIOS/UEFI but during early init (or in textmode installers like Debian netinst) it will not use those drivers and will instead rely on whatever your boot firmware provides.

Moving on…

Libreboot on x86 uses the GRUB payload by default, which means that the GRUB configuration file (where your GRUB menu comes from) is stored directly alongside libreboot and its GRUB payload executable, inside the flash chip. In context, this means that installing distributions and managing them is handled slightly differently compared to traditional BIOS systems.

On most systems, the /boot/ partition has to be left unencrypted while the others are encrypted. This is so that GRUB, and therefore the kernel, can be loaded and executed since the firmware can’t open a LUKS volume. Not so with libreboot! Since GRUB is already included directly as a payload, even /boot/ can be encrypted. This protects /boot from tampering by someone with physical access to the system.

This guide is written for Debian net installer. You can download the ISO from the homepage on debian.org. Use this on the GRUB terminal to boot it from USB (for 64-bit Intel or AMD):

set root='usb0'
linux /install.amd/vmlinuz
initrd /install.amd/initrd.gz
boot

If you are on a 32-bit system (e.g. X60):

set root='usb0'
linux /install.386/vmlinuz
initrd /install.386/initrd.gz
boot

This guide shows how to create a boot USB drive with the Debian ISO image.

This guide is only for the GRUB payload. If you use the depthcharge payload, ignore this section entirely.

Note: on some thinkpads, a faulty DVD drive can cause the cryptomount -a step during boot to fail. If this happens to you, try removing the drive.

Set a strong user password (lots of lowercase/uppercase, numbers and symbols).

Use of the diceware method is recommended, for generating secure passphrases (instead of passwords).

When the installer asks you to set up encryption (ecryptfs) for your home directory, select ‘Yes’ if you want to: LUKS is already secure and performs well. Having ecryptfs on top of it will add noticeable performance penalty, for little security gain in most use cases. This is therefore optional, and not recommended. Choose ‘no’.

Your user password should be different from the LUKS password which you will set later on. Your LUKS password should, like the user password, be secure.

Partitioning

Choose ‘Manual’ partitioning:

Further partitioning

Now you are back at the main partitioning screen. You will simply set mountpoints and filesystems to use.

Kernel

Installation will ask what kernel you want to use. linux-generic is fine, but you can choose whatever you want here.

Tasksel

For Debian, use the MATE option, or one of the others if you want. The libreboot project recommends MATE, unless you’re saavy enough to choose something else.

If you want debian-testing, then you should only select barebones options here and change the entries in /etc/apt/sources.list after install to point to the new distro, and then run apt-get update and apt-get dist-upgrade as root, then reboot and run tasksel as root. This is to avoid downloading large packages twice.

NOTE: If you want the latest up to date version of the Linux kernel, Debian’s kernel is sometimes outdated, even in the testing distro. You might consider using this repository instead, which contains the most up to date versions of the Linux kernel. These kernels are also deblobbed, like Debian’s kernels, so you can be sure that no binary blobs are present.

Postfix configuration

If asked, choose “No Configuration” here (or maybe you want to select something else. It’s up to you.)

Install the GRUB boot loader to the master boot record

Choose ‘No’, and then it will still ask you what HDD to install GRUB on. Select your HDD/SSD in the list it provides.

The installer will provide GRUB on your HDD/SSD, but not try to install it to an MBR section. However, the /boot/grub/grub.cfg on your system will be maintained automatically by apt-get when handling kernel packages.

Clock UTC

Just say ‘Yes’.

At this point, your Debian system is installed. Shut down when the installer tells you to.

LUKSv2 incompatibility

When using libreboot version 20160907 with newer Debian versions, you must downgrade LUKSv2 to LUKSv1. See debian’s cryptsetup-team page for instructions.

By default, newer versions of Debian use LUKSv2 which is technically superior to LUKSv1. However, LUKSv1 is still acceptable security-wise but lacks newer features in LUKSv2.

Libreboot 20160907 has an old version of GRUB, which lacks LUKSv2 support. If you’re using the Debian netinst it won’t have cryptsetup in it, as mentioned on that page. You can download Parabola GNU+Linux here:

64-bit ISO: https://redirector.parabola.nu/iso/x86_64-systemd-cli-2020.09/parabola-x86_64-systemd-cli-2020.09-netinstall.iso

32-bit ISO (X60, T60): https://redirector.parabola.nu/iso/i686-systemd-cli-2020.09/parabola-i686-systemd-cli-2020.09-netinstall.iso

Parabola is useful in general, not just for installing Parabola, but as a general purpose live CD for use as a rescue system since it contains virtually all of the software that you will need for this purpose. In this instance, we will use cryptsetup in Parabola to downgrade the LUKS version on your encrypted Debian installation. Parabola is a version of Arch Linux that excludes proprietary software, and it is endorsed by the Free Software Foundation.

dd it to a USB drive (use lsblk command in GNU+Linux to know which one it is), e.g.:

sudo dd if=parabola-x86_64-systemd-cli-2020.09-netinstall.iso of=/dev/sdX bs=8M conv=notrunc; sync

Replace sdX with the name that is correct on your system.

Now boot with the USB stick inserted, and press C to access the GRUB terminal. Type these commands into the GRUB terminal for the 64-bit ISO (NOTE: each command is one line below, and each command is separated by a blank line):

set root='usb0'

linux /parabola/boot/x86_64/vmlinuz parabolaisobasedir=parabola parabolaisolabel=PARA_202009

initrd /parabola/boot/x86_64/parabolaiso.img

boot

Or for 32-bit ISO:

set root='usb0'

linux /parabola/boot/i686/vmlinuz parabolaisobasedir=parabola parabolaisolabel=PARA_202009

initrd /parabola/boot/i686/parabolaiso.img

boot

When you’ve booted the live Parabola ISO, select language and it drops you to a shell. Use the lsblk command in that shell to figure out what is your encrypted partition and follow the above Debian guide to downgrade your LUKSv2 partition to LUKSv1.

After you’ve done that, it should boot.

Booting your system

If you didn’t install GRUB during the net installation process, don’t worry. You can boot your installed system manually, using the terminal in GRUB on your boot flash (the version that Libreboot gives you).

At this point, you will have finished the installation. At your GRUB payload, press C to get to the command line, and enter:

grub> cryptomount -a
grub> set root='lvm/matrix-rootvol'
grub> linux /vmlinuz root=/dev/mapper/matrix-rootvol cryptdevice=/dev/mapper/matrix-rootvol:root
grub> initrd /initrd.img
grub> boot

If you did install GRUB, ignore the above. Just select the default Load Operating System menu option and it should fully boot into your system.

When you type your encryption passphrase in GRUB, it will seem like the process has stalled. The same will be true when you load your linux kernel in Debian. Just be patient and it will boot. If you see errors, just press enter to skip them until you see the Debian GRUB menu.

ecryptfs

If you didn’t encrypt your home directory, then you can safely ignore this section.

Immediately after logging in, do that:

sudo ecryptfs-unwrap-passphrase

This will be needed in the future if you ever need to recover your home directory from another system, so write it down and keep the note somewhere secret. Ideally, you should memorize it and then burn the note (or not even write it down, and memorize it still)>

Generate distro’s grub.cfg

If /boot/grub/grub.cfg already exists, ignore this step.

Now you need to set it up so that the system will automatically boot, without having to type a bunch of commands.

Install grub-coreboot if not already installed:

# apt-get install grub-coreboot

Modify or add following lines to /etc/default/grub

GRUB_CMDLINE_LINUX="cryptdevice=/dev/mapper/matrix-rootvol:root"
GRUB_ENABLE_CRYPTODISK=y

Copy fonts/backgrounds to /boot/grub and generate grub.cfg using following command:

# grub-install --target=i386-coreboot

Refer to this guide for further guidance on hardening your GRUB configuration, for security purposes.

Troubleshooting

A user reported issues when booting with a docking station attached on an X200, when decrypting the disk in GRUB. The error AHCI transfer timed out was observed. The workaround was to remove the docking station.

Further investigation revealed that it was the DVD drive causing problems. Removing that worked around the issue.

"sudo wodim -prcap" shows information about the drive:
Device was not specified. Trying to find an appropriate drive...
Detected CD-R drive: /dev/sr0
Using /dev/cdrom of unknown capabilities
Device type    : Removable CD-ROM
Version        : 5
Response Format: 2
Capabilities   : 
Vendor_info    : 'HL-DT-ST'
Identification : 'DVDRAM GU10N    '
Revision       : 'MX05'
Device seems to be: Generic mmc2 DVD-R/DVD-RW.

Drive capabilities, per MMC-3 page 2A:

  Does read CD-R media
  Does write CD-R media
  Does read CD-RW media
  Does write CD-RW media
  Does read DVD-ROM media
  Does read DVD-R media
  Does write DVD-R media
  Does read DVD-RAM media
  Does write DVD-RAM media
  Does support test writing

  Does read Mode 2 Form 1 blocks
  Does read Mode 2 Form 2 blocks
  Does read digital audio blocks
  Does restart non-streamed digital audio reads accurately
  Does support Buffer-Underrun-Free recording
  Does read multi-session CDs
  Does read fixed-packet CD media using Method 2
  Does not read CD bar code
  Does not read R-W subcode information
  Does read raw P-W subcode data from lead in
  Does return CD media catalog number
  Does return CD ISRC information
  Does support C2 error pointers
  Does not deliver composite A/V data

  Does play audio CDs
  Number of volume control levels: 256
  Does support individual volume control setting for each channel
  Does support independent mute setting for each channel
  Does not support digital output on port 1
  Does not support digital output on port 2

  Loading mechanism type: tray
  Does support ejection of CD via START/STOP command
  Does not lock media on power up via prevent jumper
  Does allow media to be locked in the drive via PREVENT/ALLOW command
  Is not currently in a media-locked state
  Does not support changing side of disk
  Does not have load-empty-slot-in-changer feature
  Does not support Individual Disk Present feature

  Maximum read  speed:  4234 kB/s (CD  24x, DVD  3x)
  Current read  speed:  4234 kB/s (CD  24x, DVD  3x)
  Maximum write speed:  4234 kB/s (CD  24x, DVD  3x)
  Current write speed:  4234 kB/s (CD  24x, DVD  3x)
  Rotational control selected: CLV/PCAV
  Buffer size in KB: 1024
  Copy management revision supported: 1
  Number of supported write speeds: 4
  Write speed # 0:  4234 kB/s CLV/PCAV (CD  24x, DVD  3x)
  Write speed # 1:  2822 kB/s CLV/PCAV (CD  16x, DVD  2x)
  Write speed # 2:  1764 kB/s CLV/PCAV (CD  10x, DVD  1x)
  Write speed # 3:   706 kB/s CLV/PCAV (CD   4x, DVD  0x)

Supported CD-RW media types according to MMC-4 feature 0x37:
  Does write multi speed       CD-RW media
  Does write high  speed       CD-RW media
  Does write ultra high speed  CD-RW media
  Does not write ultra high speed+ CD-RW media

Copyright © 2014, 2015, 2016, 2020 Leah Rowe info@minifree.org

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License Version 1.3 or any later version published by the Free Software Foundation with no Invariant Sections, no Front Cover Texts, and no Back Cover Texts. A copy of this license is found in ../fdl-1.3.html

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