Secure Boot

Secure Boot usually refers to a platform firmware capability to verify the boot components and ensure that only your own operating system is allowed to boot.

Secure Boot has multiple implementations, the most well known one is UEFI Secure Boot, which relies on the UEFI platform firmware, but other implementations can exist on embedded systems.

Checking Secure Boot status

The easiest way to check if your machine has Secure Boot enabled is through the use of Systemd's bootctl. There is no need to be using systemd-boot as your bootloader for this command to work.

$ bootctl status
System:
    Firmware: UEFI 2.80 (American Megatrends 5.25)
    Firmware Arch: x64
    Secure Boot: enabled (user)
    TPM2 Support: yes
    Measured UKI: yes
    Boot into FW: supported
...

The system above has secure boot enabled and enforced. Other values include disabled (setup) for Setup Mode, disabled (disabled) or disabled (unsupported). The unsupported tag only appears if your device firmware does not support Secure Boot at all.

If you see disabled (disabled), this means you will need to enable Secure Boot in your UEFI firmware settings before proceeding to use one of the projects outlined below.

Enabling Secure Boot on NixOS

On NixOS, there are currently two main ways to enable Secure Boot, Lanzaboote and Limine. See their respective wiki pages for step by step instructions on each.

For Secure Boot to be most effective, there are certain conditions which should also be met. The most important are:

1. The UEFI firmware is protected by a strong password to prevent an untrusted drive from being booted or Secure Boot being disabled.
2. Full disk encryption is enabled so that your drive cannot simply be read by putting it another another machine.
3. Ideally, default OEM/third party keys are not in use as these have been shown to weaken the security of Secure Boot significantly. However, this may brick some devices which use Microsoft-signed OpROMS for certain hardware during the boot process, particularly some laptops, so you must be certain before removing them. It may be impossible to fix if, for example, the GPU relies on these OpROMS.

See Also

Arch Wiki/Secure Boot Extensive information on Secure Boot including using UKIs.