Minimal Buildroot
Trying to build a minimal buildroot for booting using emulator and as a virtual machine.
Just using the default setup from buildroot, will add custom kernel and software later.
-
board/ -
configs/
| Target | amd64 (x86_64) | arm64 (aarch64) |
|---|---|---|
| QEMU | qemu/x86_64 | qemu/aarch64-virt |
| qemu_x86_64_defconfig | qemu_aarch64_virt_defconfig | |
| UEFI | pc | aarch64-efi |
| pc_x86_64_efi_defconfig | aarch64_efi_defconfig |
Just copied these files from buildroot, since it was hard to see the forest for the trees.
Some quirks: the x86_64 targets builds ext2 (not ext4), and without support for "virtio".
The name of the kernel and format of the initrd might also vary a bit, between the arch.
kernel/
| Linux | amd64 (x86_64) | arm64 (aarch64) |
|---|---|---|
| Kernel | kernel/x86_64_defconfig | kernel/aarch64_defconfig |
| linux/arch/x86/configs/ | linux/arch/arm64/configs/ |
These default configs were copied from the Linux kernel, and seen with "make defconfig".
New targets (based on UEFI above), making an .img disk with boot/root ext4 partitions.
| amd64 (x86_64) | arm64 (aarch64) | |
|---|---|---|
| Image | img/x86_64 | img/aarch64 |
| img_x86_64_defconfig | img_aarch64_defconfig | |
| img/x86_64/linux.config | img/aarch64/linux.config |
amd64
Disk disk-amd64.img: 136,5 MiB, 142656000 bytes, 278625 sectors
Device Start End Sectors Size Type
disk-amd64.img1 64 32831 32768 16M EFI System
disk-amd64.img2 32832 278591 245760 120M Linux root (x86)
arm64
Disk disk-arm64.img: 232 MiB, 243270144 bytes, 475137 sectors
Device Boot Start End Sectors Size Id Type
disk-arm64.img1 1 65536 65536 32M ef EFI (FAT-12/16/32)
disk-arm64.img2 65537 475136 409600 200M 83 Linux
New targets (based on UEFI above), making an .iso (ISO-9660) output instead of an .img.
| amd64 (x86_64) | arm64 (aarch64) | |
|---|---|---|
| ISO | iso/x86_64 | iso/aarch64 |
| iso_x86_64_defconfig | iso_aarch64_defconfig | |
| iso/x86_64/linux-extras.config | iso/aarch64/linux-extras.config |
amd64
boot-amd64.iso
├── boot
│ ├── initrd.img
│ └── vmlinuz
├── boot.catalog
└── EFI
└── BOOT
├── bootx64.efi
├── efiboot.img
└── grub.cfg
arm64
boot-arm64.iso
├── boot
│ ├── initrd.img
│ └── vmlinuz
├── boot.catalog
└── EFI
└── BOOT
├── bootaa64.efi
├── efiboot.img
└── grub.cfg
buildroot/
This is the buildroot upstream, it is not modified except for the "output" directory.
output/
This is where the sources and build happens, and where the output ends up afterwards.
git clone --branch=2023.02.x https://github.com/buildroot/buildroot
cd buildroot
make BR2_EXTERNAL=.. <*_defconfig>
makesupport/
Support files for building, such as a container image with all required build tools.
container/
Contains helper files for constructing the container image from the rootfs archive.
93M output/images/disk-amd64.img
63M output/images/disk-arm64.img
Start the emulator directly with the kernel and the rootfs in the same terminal window.
Start the emulator with the complete system image with grub in a new graphical window.
12M output/images/boot-amd64.iso
29M output/images/boot-arm64.iso
Start the emulator directly with the kernel and the initrd in the same terminal window.
Start the emulator from the UEFI CD boot image instead of disk, otherwise same as above.