EFI Boot ISO Example

This is a simple example of how to create a bootable ISO for a computer using UEFI. A makefile is included which automates the downloading of a test Linux kernel and initfs (Slackware current 64bit) and generating the bootable ISO and requisite files/images using the base tools.

The general flow of creating a bootable ISO for UEFI systems is:

1. Create an UEFI Grub image with a stub config and minimal modules.
2. Create a vfat image file to use as the UEFI ESP (EFI System Partition).
3. Create the ISO with the kernel images, ESP image file, Grub modules, and full using mkisofs.

Create directory structure and download files

Create directories and change CWD:

mkdir -p efibootiso
cd efibootiso
mkdir -p EFI/BOOT
mkdir -p boot/grub/x86_64-efi

Download Slackware files:

curl \
   -o boot/vmlinuz \
   https://mirrors.kernel.org/slackware/slackware64-current/kernels/huge.s/bzImage
curl \
   -o boot/initrd.img \
   https://mirrors.kernel.org/slackware/slackware64-current/isolinux/initrd.img

Create bootx64.efi

Copy grub modules:

cp /usr/lib64/grub/x86_64-efi/*.mod boot/grub/x86_64-efi/

Create stub grub configuration:

cat << EOF > grub-stub.cfg

insmod all_video
insmod efi_gop
insmod efi_uga
insmod video_bochs
insmod video_cirrus

insmod iso9660
insmod udf

search --no-floppy --label EFIBOOTISO --set root
set prefix=($root)/boot/grub

configfile /grub.cfg

EOF

Create grub image:

grub-mkimage \
   -o EFI/BOOT/bootx64.efi \
   -c grub-stub.cfg \
   -p /boot/grub \
   -O x86_64-efi \
   efi_gop efi_uga efinet \
   all_video video video_bochs video_cirrus video_fb videoinfo \
   serial \
   terminfo terminal \
   search search_fs_file search_fs_uuid search_label \
   udf iso9660 ext2 fat exfat ntfs hfsplus \
   part_gpt part_msdos msdospart lvm diskfilter parttool probe \
   normal \
   acpi ohci uhci ahci ehci \
   cat ls chain configfile echo halt reboot \
   ls lsefimmap lsefisystab lsmmap lspci lsacpi lssal \
   linux

Create UEFI ESP (EFI System Partition) Image

Create empty file to use as disk image:

dd if=/dev/zero of=EFI/BOOT/efiboot.img bs=512 count=2880

Create MSDOS filesystem:

mkfs.msdos -F 12 -n 'EFIBOOTISO' EFI/BOOT/efiboot.img

Create directory structure:

mmd -i EFI/BOOT/efiboot.img ::EFI
mmd -i EFI/BOOT/efiboot.img ::EFI/BOOT

Copy grub image into disk image file:

mcopy -i EFI/BOOT/efiboot.img EFI/BOOT/bootx64.efi ::EFI/BOOT/bootx64.efi

Create UEFI bootable ISO image

Create full grub configuration:

cat << EOF > grub.cfg

serial --unit 4 --speed 9600
terminal_input  serial console
terminal_output serial console

set pager=1

menuentry --hotkey=l 'Linux' {
   echo   'Loading /boot/vmlinuz ...'
   linux  /boot/vmlinuz \
          console=tty0 \
          rw
   echo   'Loading /boot/initrd.img ...'
   initrd /boot/initrd.img
}
menuentry --hotkey=p 'List PCI' {
   lspci
}
menuentry --hotkey=r 'Reboot' {
   reboot
}
menuentry --hotkey=h 'Halt' {
   halt
}

EOF

Create ISO image with mkisofs:

mkisofs \
   -o efiboot.iso \
   -R -J -v -d -N \
   -x efiboot.iso \
   -hide-rr-moved \
   -no-emul-boot \
   -eltorito-platform efi \
   -eltorito-boot EFI/BOOT/efiboot.img \
   -V "EFIBOOTISO" \
   -A "EFI Boot ISO Test"  \
   .