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1# LUKS-Encrypted File Systems {#sec-luks-file-systems}
2
3NixOS supports file systems that are encrypted using *LUKS* (Linux
4Unified Key Setup). For example, here is how you create an encrypted
5Ext4 file system on the device
6`/dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d`:
7
8```ShellSession
9# cryptsetup luksFormat /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d
10
11WARNING!
12========
13This will overwrite data on /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d irrevocably.
14
15Are you sure? (Type uppercase yes): YES
16Enter LUKS passphrase: ***
17Verify passphrase: ***
18
19# cryptsetup luksOpen /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d crypted
20Enter passphrase for /dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d: ***
21
22# mkfs.ext4 /dev/mapper/crypted
23```
24
25The LUKS volume should be automatically picked up by
26`nixos-generate-config`, but you might want to verify that your
27`hardware-configuration.nix` looks correct. To manually ensure that the
28system is automatically mounted at boot time as `/`, add the following
29to `configuration.nix`:
30
31```nix
32boot.initrd.luks.devices.crypted.device = "/dev/disk/by-uuid/3f6b0024-3a44-4fde-a43a-767b872abe5d";
33fileSystems."/".device = "/dev/mapper/crypted";
34```
35
36Should grub be used as bootloader, and `/boot` is located on an
37encrypted partition, it is necessary to add the following grub option:
38
39```nix
40boot.loader.grub.enableCryptodisk = true;
41```
42
43## FIDO2 {#sec-luks-file-systems-fido2}
44
45NixOS also supports unlocking your LUKS-Encrypted file system using a
46FIDO2 compatible token. In the following example, we will create a new
47FIDO2 credential and add it as a new key to our existing device
48`/dev/sda2`:
49
50```ShellSession
51# export FIDO2_LABEL="/dev/sda2 @ $HOSTNAME"
52# fido2luks credential "$FIDO2_LABEL"
53f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7
54
55# fido2luks -i add-key /dev/sda2 f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7
56Password:
57Password (again):
58Old password:
59Old password (again):
60Added to key to device /dev/sda2, slot: 2
61```
62
63To ensure that this file system is decrypted using the FIDO2 compatible
64key, add the following to `configuration.nix`:
65
66```nix
67boot.initrd.luks.fido2Support = true;
68boot.initrd.luks.devices."/dev/sda2".fido2.credential = "f1d00200108b9d6e849a8b388da457688e3dd653b4e53770012d8f28e5d3b269865038c346802f36f3da7278b13ad6a3bb6a1452e24ebeeaa24ba40eef559b1b287d2a2f80b7";
69```
70
71You can also use the FIDO2 passwordless setup, but for security reasons,
72you might want to enable it only when your device is PIN protected, such
73as [Trezor](https://trezor.io/).
74
75```nix
76boot.initrd.luks.devices."/dev/sda2".fido2.passwordLess = true;
77```