efitools is a set of tools for manipulating EFI secure boot platforms. If you ever plan to use LockDown.efi (it's an EFI program that installs a predefined set of Secure Boot keys if you run it while your machine is in setup mode) you will want to use your own Secure Boot keys and maybe specify an owner GUID (in hex). The keys should be placed in the SlackBuild directory and named: Platform Key public/private keys - PK.crt, PK.key Key Exchange public/private keys - KEK.crt, KEK.key Signature Database public/private keys - DB.crt, DB.key and the SlackBuild should be executed using: GUID=xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx USE_KEYS=yes ./efitools.SlackBuild It's unlikely that you'll use LockDown.efi and there are alternate methods to do what it does, so it's fine just to ignore it.