This article explains how to create an UEFI boot USB with parted and gummiboot.
In this example we will use /dev/sdX. This will be different depending on your system.
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 efi binary
UEFI will look for a EFI/bootx64.efi as a fallback efi loader. We copy bootx64.efi to this location.
Create configuration files for boot loader
We need create some configuration files for gummiboot.
The options are taken from boot/syslinux/syslinux.cfg
Finally umount the disk