airgap/Containerfile

FROM stagex/busybox AS busybox
FROM stagex/musl AS musl
FROM stagex/xorriso AS xorriso
FROM stagex/syslinux AS syslinux
FROM stagex/cpio AS cpio
FROM stagex/linux-airgap AS linux
FROM stagex/mtools AS mtools
FROM stagex/xz AS xz
FROM stagex/grub:local AS grub

FROM scratch AS base
COPY --from=busybox . /
COPY --from=musl . /
COPY --from=xorriso . /
COPY --from=cpio . /
COPY --from=mtools . /
COPY --from=linux . /
COPY --from=syslinux . /
COPY --from=xz . /
COPY --from=grub . /

FROM base AS build

## Kernel
COPY --from=linux /bzImage iso/boot/vmlinuz

## Initramfs
COPY --from=stagex/busybox . initramfs
COPY --chmod=0755 <<-EOF initramfs/init
    #!/bin/sh
    /bin/sh
EOF
RUN <<-EOF
    set -eux
    cd initramfs
    find . \
        | cpio -o -H newc \
        | gzip -9 \
    > ../iso/boot/initramfs
EOF

## Grub (EFI Boot)
COPY <<-EOF iso/boot/grub/grub.cfg
    menuentry "Linux Airgap" {
	    linux	/boot/vmlinuz
		initrd	/boot/initramfs
    }
EOF
COPY <<-EOF grub_early.cfg
	search --no-floppy --set=root --label "Airgap"
	set prefix=(\$root)/boot/grub
EOF
RUN <<-EOF
    set -eux
    mkdir -p iso/efi/boot
    grub-mkimage \
		--config="grub_early.cfg" \
		--prefix="/boot/grub" \
		--output="iso/efi/boot/bootx64.efi" \
		--format="x86_64-efi" \
        --compression="xz" \
		all_video \
        disk \
        part_gpt \
        part_msdos \
        linux \
        normal \
        configfile \
        search \
        search_label \
        efi_gop \
        fat \
        iso9660 \
        cat \
        echo \
        ls \
        test \
        true \
        help \
        gzio
EOF
RUN <<-EOF
    mformat -i iso/boot/grub/efi.img -C -f 1440 -N 0 ::
    mcopy -i iso/boot/grub/efi.img iso/efi
    touch -md "@0" iso/boot/grub/efi.img
EOF


## Syslinux (BIOS Boot)
COPY <<-EOF iso/boot/syslinux/syslinux.cfg
    TIMEOUT 2
    PROMPT -1
    DEFAULT Airgap
    LABEL Airgap
        MENU LABEL Linux Airgap
        KERNEL /boot/vmlinuz
        INITRD /boot/initramfs
EOF
RUN <<-EOF
    mkdir -p iso/boot/syslinux
    for file in \
        isohdpfx.bin \
        isolinux.bin \
        ldlinux.c32 \
        libutil.c32 \
        libcom32.c32 \
        mboot.c32; \
    do
		mv /usr/share/syslinux/$file iso/boot/syslinux/$file || return 1
	done
EOF

## Build Hybrid EFI/BIOS ISO
FROM build AS install
RUN xorrisofs \
    -output airgap.iso \
    -full-iso9660-filenames \
    -joliet \
    -rational-rock \
    -sysid LINUX \
    -isohybrid-mbr iso/boot/syslinux/isohdpfx.bin \
    -eltorito-boot boot/syslinux/isolinux.bin \
    -eltorito-catalog boot/syslinux/boot.cat \
    -no-emul-boot \
    -boot-load-size 4 \
    -boot-info-table \
    -eltorito-alt-boot \
    -e boot/grub/efi.img \
    -no-emul-boot \
    -isohybrid-gpt-basdat \
    -follow-links \
   iso/

FROM scratch AS package
COPY --from=install /iso /iso
COPY --from=install /airgap.iso /