Enable Measured Boot

This guide will walk you through enabling Measured Boot on a system that already has some form of LUKS2 disk encryption and migrating this LUKS2 volume to Measured Boot.

Note

We do not support filesystem level encryption via ZFS or brtfs.

While you will be able to use this same basic mechanism (i.e. a managed TPM2 policy) for unlocking filesystem level encryption, there is no integration we provide for it. You will have to implement this yourself.

Enable Measured Boot in Your Config

Note

If you enable Measured Boot, the maximum allowed configurationLimit is 8. This limit is enforced by systemd-pcrlock which currently won’t create a policy for more than 8 variants.

boot.initrd.systemd.enable = true;
boot.lanzaboote = {
  measuredBoot = {
    enable = true;
    pcrs = [
      0
      4
      7
    ];
  };
};

The additional pcrs entries 1, 2 and 3 might be flaky. You have try out how they behave on you hardware. See the explanation page for measured boot.

Switch to the New Generation

Switch to the new generation:

nixos-rebuild boot

Note

If you’re using an ephemeral root, you need to persist boot.lanzaboote.measuredBoot.pcrlockPolicy and boot.lanzaboote.measuredBoot.pcrlockDirectory across reboots.

Now reboot:

reboot

Enroll the Policy

Caution

Always enroll some form of recovery key or passphrase!

systemd-pcrlock is still considered experimental by systemd. So to avoid data loss in the case of misconfiguration or other TPM issues, you should have some way to manually unlock your volume.

For an attended system like a workstation, you should enforce some kind of user secret in addition to the TPM for unlocking your encrypted (root) volume. Thus, use the option --tpm2-with-pin=true for systemd-cryptenroll.

systemd-cryptenroll \
  --tpm2-device=auto \
  --tpm2-with-pin=true \
  --tpm2-pcrlock=/var/lib/systemd/pcrlock.json \
  /dev/sdX

Congratulations, you are now a proud user of Measured Boot! You will not need to re-enroll anything into your LUKS2 volume. Lanzaboote will automatically take care of creating measurements and updating the TPM policy whenever you update your system via nixos-rebuild.