folk-live-build

Builds a bootable Folk OS image.

To run Folk on a PC, download the latest pre-built Folk image for USB stick from the Releases page. Follow the instructions there.

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Below are details on how the Folk OS image is constructed; you don't need to worry about any of the below if you're just trying to install Folk.

Key files

• folk-live/: becomes writable partition on disk, including Folk repo
• config/package-lists/folk.list.chroot: apt packages
• config/hooks/normal/9999-setup-folk.hook.chroot: executed in / chroot at image construction time
• config/includes.chroot_after_packages/: copied into / at boot
• config/includes.chroot_after_packages/lib/live/config/9999-folk: executed at boot

How to build folk-amd64.img from scratch

You need to build on a computer running amd64 Debian Bookworm. (Use a virtual machine if you need to. A Folk system built by folk-live-build itself should work, though, whether on a virtual or physical machine.)

# apt install live-build parted dosfstools zip
$ git submodule update --init
$ make

emits folk-amd64.img.

(It runs from scratch each time -- can take 30 minutes or more.)

How it works

Image (-> USB drive) contains Master Boot Record with:

1. 'Binary' ext4 partition (~1.3GB)

   • Contains a bunch of stuff (?), including the SquashFS file of the chroot filesystem, which ultimately maps to / in the running system
   • Could be fat32 or iso9660 I think but ext4 is reliable

2. EFI system partition (100MB)

   • syslinux-efi bootloader
   • Linux kernel image (annoying if you update kernel but this is a sealed live USB so that shouldn't be an issue)

3. Writable FAT32 partition (~500MB)

   • Contains /folk with Folk evaluator code and virtual programs, /folk-printed-programs, etc.
   • Contains setup.folk which you can edit to set runtime settings (Wi-Fi credentials)
   • Designed to automount on all operating systems when the USB is plugged in, to make it easy to configure Wi-Fi and other stuff before boot

Cannot have FAT32 partition be same as efi partition (and use iso loopback) because macOS (and probably other OSes?) won't automount an efi partition.

Build process

The build process uses Debian live-build to build a live image, then appends EFI system partition (to make it bootable on UEFI machines) and a writable partition (to make it easy for end-user to set config settings and update Folk).

(live-build can make a complete bootable disk image on its own, but only in iso-hybrid mode, which doesn't let you modify the partition table to add the writable partition, so we instead use hdd mode and modify the partition table ourselves.)

1. Run live-build, emit a disk image (with MBR with only a binary partition. not bootable on many modern systems)

2. Use parted to mutate the disk image to add EFI system partition

3. Copy syslinux-efi bootloader and bootloader config and Linux kernel etc onto EFI system partition

4. Use parted to mutate the disk image to add the writable FAT32 partition

References

• https://ianlecorbeau.github.io/blog/debian-live-build.html
• https://manpages.debian.org/testing/live-build/lb_config.1.en.html
• https://live-team.pages.debian.net/live-manual/html/live-manual/index.en.html

License

Apache 2.0

TODO

• Replace "NO NAME" title of FAT32 writable partition with Folk name
• Test MBR+EFI on various systems (BIOS, UEFI, Chromebook, Beelink, NUC, UTM)
• Make fstab automount the writable partition (how do we know it's /dev/sdb2?)
• Put Wi-Fi config on writable partition
• Allow setting display and webcam from setup.folk
• Figure out disk installation process
• Handle printed programs, calibration (make folk prefix that goes to folk-live?)