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

Install parted

apk add parted

Create a single UEFI boot partitions.

Warning: This will erase all content of your /dev/sdX. Make sure that you use correct device.

parted --script /dev/sdX mklabel gpt parted --script --align=optimal /dev/sdX mkpart ESP fat32 1MiB 100% parted --script /dev/sdX set 1 boot on

Create fat32 filesystem

Create a fat32 system with the name `Alpine`.

mkfs.vfat -n ALPINE /dev/sdX1

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 alpine-conf package.

mount -t vfat /dev/sdX1 /mnt cd /mnt uniso < /path/to/alpine-3.8.2-x86_64.iso

Create MOK Key

openssl req -new -x509 -newkey rsa:2048 -keyout $HOME/alpine_local.key -out $HOME/alpine_local.crt -nodes -days 3650 -subj "/CN=Alpine Local CA/" openssl x509 -in $HOME/alpine_local.crt -out $HOME/alpine_local.cer -outform DER

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.

cd /mnt/efi/boot unzip /path/to/refind-bin-0.11.4.zip mv refind-bin-0.11.4/refind/* . rm -rf refind-bin-0.11.4

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.

cd /mnt/efi/boot gunzip -c /path/to/shim-signed-0.2.tgz | tar x --strip-components=1 --no-same-owner

Install Shim and Certificate

cp $HOME/alpine_local.cer /mnt/efi/boot cp /mnt/efi/boot/refind_x64.efi /mnt/efi/boot/grubx64.efi cp /mnt/efi/boot/shim.efi /mnt/efi/boot/bootx64.efi

Sign the Bootloader and kernel with your key

sbsign --key $HOME/alpine_local.key --cert $HOME/alpine_local.crt /mnt/efi/boot/grubx64.efi mv /mnt/efi/boot/grubx64.efi.signed /mnt/efi/boot/grubx64.efi sbsign --key $HOME/alpine_local.key --cert $HOME/alpine_local.crt /mnt/boot/vmlinuz-vanilla mv /mnt/boot/vmlinuz-vanilla.signed /mnt/boot/vmlinuz-vanilla

Unmount the partition

Finally umount the disk

cd ~ && umount /mnt

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.