Create UEFI secureboot USB
This article explains how to create an UEFI boot USB with parted and rEFInd. Unfortunately the version of GRUB that ships with ALpine Linux did not work and Gummiboot only worked on one of two machines I tested. I will submit a PR for a rEFInd package and update these instructions to simplify them given time.
In this example we will use /dev/sdX and $HOME. This will be different depending on your system. Substitute the paths in the examples below as necessary.
Create GPT boot partition
Create a single UEFI boot partitions.
Create fat32 filesystem
Create a fat32 system with the name `Alpine`.
Copy content of ISO image to filesystem
It is possible to mount the iso image and copy files with cp or rsync and it is also possible to use 7z to extract content from the iso. In this example I will use the uniso utility from package.
Create MOK Key
Download and install rEFInd
Download the binary zip file of rEFInd from http://www.rodsbooks.com/refind/getting.html. In this example we will use the current version of rEFInd, refind-bin-0.11.4.zip. There may be a more recent version of rEFInd available when you download.
Copy signed shim
Download Matthew J. Garrett's signed shim from http://www.codon.org.uk/~mjg59/shim-signed/shim-signed-0.2.tgz. In this example we assume it is stored in your users download directory. Substitute the paths in the example below as necessary.
Install Shim and Certificate
Sign the Bootloader and kernel with your key
Unmount the partition
Finally umount the disk
Install the Keys and Enroll Hash
Insert the USB into the target PC and boot. When prompted select to enroll key, navigate to alpine_local.cer and add it. Then select enroll hash navigate to efi/boot/grubx64.efi select it and add the hash. Now reboot and given a bit of luck it should launch alpine. This step is a bit more complex than it needs to be due to the binary distribution of refind already being signed by the authors key. Once rEFInd is packaged it should simplify this step.