NixOS install with encrypted /boot /root with single password unlock

encryptedNixos.md

Requirements

1. Encrypt everthing including /boot and /root
2. Enter password once
3. Support UEFI

Installation media setup

Download NixOS minimal iso and copy to USB stick. For example on Mac OSX

$ diskutil list
$ diskutil unmountDisk /dev/disk1 # Make sure you got right device
$ dd if=nixos-minimal-20.09.2405.e065200fc90-x86_64-linux.iso of=/dev/disk1

NixOS install

Boot from the USB stick and setup networking. (optionally setup SSH if you want to complete the install from another computer)

$ wpa_passphrase SSID 'PASSWORD' > /etc/wpa_supplicant.conf
$ systemctl start wpa_supplicant
$ systemctl start sshd
$ passwd # So we can login via SSH

Partitioning

I have 2 drives on my system: NVME SSD and a regular SATA drive. This is what the drives should look like after install. I use NVME SSD for booting and SATA drive as a /data mount.

NAME             MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                8:0    0 931.5G  0 disk
└─sda1             8:1    0 931.5G  0 part
  └─crypted-data 254:3    0 931.5G  0 crypt /data
nvme0n1          259:0    0 465.8G  0 disk
├─nvme0n1p1      259:1    0   549M  0 part  /boot/efi
└─nvme0n1p2      259:2    0 465.2G  0 part
  └─root         254:0    0 465.2G  0 crypt
    ├─vg-swap    254:1    0     4G  0 lvm   [SWAP]
    └─vg-root    254:2    0 461.2G  0 lvm   /

The only unecrypted partition is nvme0n1p1, which is mounted on /boot/efi. But rest of /boot is encrypted along with swap and root. /dev/sda1 is also encrypted and mounted as /data (Note: If you plan on extending /data with more drives, you should do LUKS-on-LVM )

Use Use gdisk to partition the drives

$ gdisk /dev/nvme0n1

• o Create partition table
• n Create new partition of size 550M and of type ef00
• n Create another partition of type 8300 and use remainig space
• p Show what gdisk will write
• w Write to disk an exit

$ gdisk /dev/sda

• o Create partition table
• n Create another partition of type 8300 and use all space
• p Show what gdisk will write
• w Write to disk an exit

Generate keys for single password unlock

$ dd if=/dev/urandom of=./keyfile0.bin bs=1024 count=4
$ dd if=/dev/urandom of=./keyfile1.bin bs=1024 count=4

Setup LUKS and add the keys

# Enter the passphrase which is used to unlock disk. You will enter this in grub on every boot
$ cryptsetup luksFormat --type luks1 -c aes-xts-plain64 -s 256 -h sha512 /dev/nvme0n1p2

# Add a second key which will be used by nixos. You will need to enter the pasphrase from previous step
$ cryptsetup luksAddKey /dev/nvme0n1p2 keyfile0.bin
$ cryptsetup luksOpen /dev/nvme0n1p2 crypted-nixos -d keyfile0.bin

# For /data just the second random generated key
$ cryptsetup luksFormat -c aes-xts-plain64 -s 256 -h sha512 /dev/sda1 -d keyfile1.bin
$ cryptsetup luksOpen /dev/sda1 crypted-data -d keyfile1.bin

Setup LVM

$ pvcreate /dev/mapper/crypted-nixos
$ vgcreate vg /dev/mapper/crypted-nixos
$ lvcreate -L 4G -n swap vg
$ lvcreate -l '100%FREE' -n root vg

Format the partitions and mount

$ mkfs.fat -F 32 /dev/nvme0n1p1
$ mkswap -L swap /dev/vg/swap
$ mkfs.ext4 -L root /dev/vg/root
$ mkfs.ext4 -L data /dev/mapper/crypted-data

$ mount /dev/vg/root /mnt
$ mkdir -p /mnt/boot/efi
$ mount /dev/nvme0n1p1 /mnt/boot/efi
$ swapon /dev/vg/swap

Copy the keys

$ mkdir -p /mnt/etc/secrets/initrd/
$ cp keyfile0.bin keyfile1.bin /mnt/etc/secrets/initrd
$ chmod 000 /mnt/etc/secrets/initrd/keyfile*.bin

Generate and edit configuration

$ nixos-generate-config --root /mnt

Add the following to /mnt/etc/nixos/configuration.nix

  boot.loader.efi.canTouchEfiVariables = true;
  boot.loader.efi.efiSysMountPoint = "/boot/efi";
  boot.loader.grub = {
    enable = true;
    device = "nodev";
    version = 2;
    efiSupport = true;
    enableCryptodisk = true;
  };
  
  boot.initrd = {
    luks.devices."root" = {
      device = "/dev/disk/by-uuid/a8b302cf-5296-4a2e-a7ba-707e6fa75123"; # UUID for /dev/nvme01np2 
      preLVM = true;
      keyFile = "/keyfile0.bin";
      allowDiscards = true;
    };
    secrets = {
      # Create /mnt/etc/secrets/initrd directory and copy keys to it
      "keyfile0.bin" = "/etc/secrets/initrd/keyfile0.bin";
      "keyfile1.bin" = "/etc/secrets/initrd/keyfile1.bin";
    };
};

# Data mount
fileSystems."/data" = {
  device = "/dev/disk/by-uuid/79630267-5766-4c7d-85a5-1d5f1dcd58ad"; # UUID for /dev/mapper/crypted-data
  encrypted = {
    enable = true;
    label = "crypted-data";
    blkDev = "/dev/disk/by-uuid/3476cb09-b3c4-4301-9ec9-84f60f32828a"; # UUID for /dev/sda1
    keyFile = "/keyfile1.bin";
  };
};
  

You can get the UUIDs by running

$ blkid

Install NixOS and reboot

$ nixos-install
$ reboot

Thats it! Once you reboot, GRUB will ask for the password. If password is correct, GRUB will show you the NixOS system profiles menu. After that, your system will boot without asking for the disk password.

Future work

If I enter an incorrect disk password, GRUB does not handle it gracefully. It will drop me into a shell without re-prompting for a password. I have to run the following commands for it to prompt again. Need to figure out if GRUB has an option for it to re-prompt.

cryptomount hdX,gptY    # Device to mount: drive X, GPT partition Y, this forces the re-prompt.
insmod normal           # Load the normal mode boot module.
normal                  # Enter normal mode and display the GRUB menu.

Credits

• Installation of NixOS with encrypted root by martijnvermaat
• Full disk encryption with LUKS (including /boot) by Pavel Kogan
• dm-crypt/Encrypting an entire system by ArchLinux wiki
• EmilGedda
• ElvishJerricco
• whoizit
• starfys
• WolfangAukang
• Dom-R

I've updated the doc. Thank you everyone for the feedback!

grub merged LUKS2 support in Jan 2020, It should work in theory.

grub merged LUKS2 support in Jan 2020, It should work in theory.

Thanks for the heads up!

Here is ref:

https://git.savannah.gnu.org/cgit/grub.git/log/

https://git.savannah.gnu.org/cgit/grub.git/commit/?id=ec46685ed4ea7bf0dd81c8254c2d9e0e8514976c (last commit with luks2 message)

grub merged LUKS2 support in Jan 2020, It should work in theory.

Yet at time of writing GRUB is still in version 2.04 from 2019! So no, LUKS2 is not working at the moment.
The next major release of GRUB 2.06 is expected in April 2021 and hopefully lands of NixOS soon after.

I just wanted to share that we have now grub 2.06~rc1 in nixos stable. Sadly booting from a luks2 header failed for me without helpful error message. (It just doesn‘t decrypt on boot.) With luks1 header this guide works fine.

EDIT: Maybe this is because I had an argon2i header on the disk, but the key I wanted grub to unlock was pkdf2.

Tried with luks2 on 21.05 and grub still fails.

Btw, what do you think about switching on the readme the path to the configuration file to /mnt/etc/nixos/configuration.nix? I got confused and ended up actually changing /etc instead of /mnt/etc.

Let's just say that I spent a stupid amount of time trying to fix an error caused by my stupidity. 🤦

Good suggestion @Dom-R. Updated the doc

FYI, for the people that is following this guide and using the 21.11 image as of now (Dec 2021), you might find with this issue. In summary, the error mktemp: failed to create directory via template ‘/mnt/tmp.kYftcsVwDN/initrd-secrets.XXXXXXXXXX’: No such file or directory might show up.

Just run nixos-install normally, then (as nixos user) run sudo nixos-enter and finally nixos-install --root /. There might be some warnings, but as long as it asks you for a new password, everything is fine (or at least it worked for me).

Finally, one addition to the guide if someone has no problem in using systemd-boot instead of grub:

boot.loader = {
  efi.canTouchEfiVariables = true;
  systemd-boot = {
    enable = true;
    configurationLimit = 20; # You can leave it null for no limit, but it is not recommended, as it can fill your boot partition.
  };
};

I had to use /dev/disk/by-partuuid/UUID instead of /dev/disk/by-uuid/UUID, in my case LUKS partition created on external SSD didn't show up in /dev/disk/by-uuid/.
I was able to install NixOS 21.11, using the same workaround @WolfangAukang mentioned.

@sarveshrulz this is weird. Last weekend I ran a nixos-install from a flake, using this guide, and it worked normally. Here is my config if you want a reference.

@sarveshrulz this is weird. Last weekend I ran a nixos-install from a flake, using this guide, and it worked normally. Here is my config if you want a reference.

My bad, it was cuz my initrd was lz4, sorry and thank you

@WolfangAukang afaik systemd boot can't work with encrypted /boot so following this guide for systemd-boot would be terrible because your keyfiles will reside unencrypted in /boot making FDE completely useless.

@WolfangAukang afaik systemd boot can't work with encrypted /boot so following this guide for systemd-boot would be terrible because your keyfiles will reside unencrypted in /boot making FDE completely useless.

I've only provided an alternative as there has been people reluctant in using GRUB, but it is their responsibility in investigating and knowing the consequences before doing this. The guide is originally using GRUB.

@WolfangAukang afaik systemd boot can't work with encrypted /boot so following this guide for systemd-boot would be terrible because your keyfiles will reside unencrypted in /boot making FDE completely useless.

I've only provided an alternative as there has been people reluctant in using GRUB, but it is their responsibility in investigating and knowing the consequences before doing this. The guide is originally using GRUB.

I understand but in this case it is not an alternative and IMO it's dangerous to suggest using it since it could lead people into believing they have FDE when in reality their keyfile is sitting unencrypted in /boot. I think you should add this information as a disclaimer in the guide to keep people safe.

There is no grub1 in NixOS anymore?
I got an error that:
boot.loader.grub.version does not have any effect anymore, please remove it from your configuration