LUKS-Encrypted File Systems {#sec-luks-file-systems}#

NixOS supports file systems that are encrypted using LUKS (Linux Unified Key Setup). For example, here is how you create an encrypted Ext4 file system on the device /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d:

# cryptsetup luksFormat /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d

WARNING!
========
This will overwrite data on /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d irrevocably.

Are you sure? (Type uppercase yes): YES
Enter LUKS passphrase: ***
Verify passphrase: ***

# cryptsetup luksOpen /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d crypted
Enter passphrase for /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d: ***

# mkfs.ext4 /dev/mapper/crypted

The LUKS volume should be automatically picked up by nixos-generate-config, but you might want to verify that your hardware-configuration.nix looks correct. To manually ensure that the system is automatically mounted at boot time as /, add the following to configuration.nix:

boot.initrd.luks.devices.crypted.device = "/dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d";
fileSystems."/".device = "/dev/mapper/crypted";

Should grub be used as bootloader, and /boot is located on an encrypted partition, it is necessary to add the following grub option:

boot.loader.grub.enableCryptodisk = true;

FIDO2 {#sec-luks-file-systems-fido2}#

NixOS also supports unlocking your LUKS-Encrypted file system using a FIDO2 compatible token. In the following example, we will create a new FIDO2 credential and add it as a new key to our existing device /dev/sda2:

# export FIDO2_LABEL="/dev/sda2 @ $HOSTNAME"
# fido2luks credential "$FIDO2_LABEL"
f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7

# fido2luks -i add-key /dev/sda2 f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7
Password:
Password (again):
Old password:
Old password (again):
Added to key to device /dev/sda2, slot: 2

To ensure that this file system is decrypted using the FIDO2 compatible key, add the following to configuration.nix:

boot.initrd.luks.fido2Support = true;
boot.initrd.luks.devices."/dev/sda2".fido2.credential = "f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7";

You can also use the FIDO2 passwordless setup, but for security reasons, you might want to enable it only when your device is PIN protected, such as Trezor.

boot.initrd.luks.devices."/dev/sda2".fido2.passwordLess = true;