Matching coherent-shell boot image: operator preparation

The latest host-built candidate is source 017125c8, image /nix/store/i0mp5wbp5gjyrb5x69g6n9hm5khawr82-k230-sd-image.img. Its separate inspection record pins the image and all eight boot-file hashes. It names the same /nix/store/48x70j3df8ksiyab0sdgas5nzmgx69nz-nixos-system-nixos-26.11.20260919.20b1ddd system that was guarded-test-activated for the supervised keyboard preview. The earlier integrated image record remains unchanged as evidence for its own 6ed24efb source and 5xm4… system.

This change adds .#sdImage-coherent using the same mkBoardImage function as the existing normal .#sdImage. It selects the opt-in k230-coherent-shell NixOS configuration. The normal image remains the bar-session rollback. A matching integrated image was later built and inspected on the host; no SD write, boot-file change, reboot, or new physical observation is claimed here. The installed coherent system was last test-activated, not selected for ordinary boot; its latest proof is the supervised keyboard preview.

On the host, after the sole Nix build slot is released, build and record the two identities together:

nix eval --raw .#nixosConfigurations.k230-coherent-shell.config.system.build.toplevel
nix eval --raw .#sdImage-coherent.drvPath
nix build .#sdImage-coherent --max-jobs 1 --cores 4 --no-link --print-out-paths

The image is the existing SD layout: boot ext4 starts at byte 4 MiB, spans 112 MiB, and contains Image, initrd.uimg, k230-tdisplay.dtb, bootargs.txt, fw_jump_add_uboot_head.bin and the DTB selector files. Before any selection, extract those files on the host and hash them. Substitute the exact built image path and create a new private output directory; these commands only read the image. Confirm the sfdisk output shows boot start 8192 and size 229376 in 512-byte sectors before using the fixed dd offsets below.

image=/nix/store/REPLACE-WITH-EXACT-k230-sd-image.img
boot_dir=$(mktemp -d)
sfdisk -d "$image"
dd if="$image" of="$boot_dir/boot.ext4" bs=1M skip=4 count=112 status=none
for name in Image initrd.uimg k230-tdisplay.dtb bootargs.txt fw_jump_add_uboot_head.bin force_dtb lcd_dtb hdmi_dtb; do
  debugfs -R "dump /$name $boot_dir/$name" "$boot_dir/boot.ext4"
done
sha256sum "$boot_dir"/{Image,initrd.uimg,k230-tdisplay.dtb,bootargs.txt,fw_jump_add_uboot_head.bin,force_dtb,lcd_dtb,hdmi_dtb}

Check that bootargs.txt has exactly one init= token and it names the evaluated coherent system plus /init. Compare all eight file hashes with the running card before deciding which files need replacement. The previous root-growth selection imported the whole matching closure and found kernel/initrd hashes unchanged, so it replaced only differing bootargs.txt and DTB bytes. That prior comparison does not establish that this coherent candidate has the same kernel/initrd; repeat it on the exact candidate. Preserve the current boot files, system profile, and a byte-verified recovery image before any write. During the later guarded selection, register the newly selected system in the durable /nix/var/nix/profiles/system profile and retain the previous system through a separate durable GC root or verified retained profile generation. Check both roots before reboot: an absolute init=/nix/store/... in bootargs.txt does not protect that store closure from garbage collection. On a failed ordinary boot, a Linux rollback timer cannot run; use the preserved boot selection or the proved USB recovery route.

This board’s external bootloader install hook is a no-op. U-Boot imports the fixed /boot/bootargs.txt and its init= names a system store path, so switch-to-configuration test, a profile change, or switch-to-configuration boot alone does not make the coherent shell survive restart. Physical task 5.8 requires a later reserved-board file selection or full-image flash, a fresh ordinary boot, exact /run/current-system and service checks, and the selected theme appearing again. The theme’s private current/active pointer is designed to survive a service restart, but this document provides no reboot proof.

Exact integrated host build

At source 6ed24efb (including the final keyboard source), the command above passed and produced /nix/store/x0dpxdq2lc8ic9z8hd11ysnfr7cz9w2s-k230-sd-image.img. The structured host inspection records the full revision, image SHA256, derivation, eight extracted boot-file hashes and check results. The image’s single init= token names the built coherent system /nix/store/5xm4bwka6waggamz9i48ljjp3yilaf6c-nixos-system-nixos-26.11.20260919.20b1ddd/init. Its Image bytes match that system’s kernel; the U-Boot ramdisk has the expected image magic and its payload byte-matches that system’s initrd. The decompiled image DTB differs from the pinned source DTB only by the inserted /chosen/bootargs. The normal image derivation remains distinct. This is host-built artifact identity only; reboot selection, GC roots and restored theme on glass remain open physical work.

Evaluated from this source checkpoint (before the final keyboard source was integrated, so these are provisional identities): coherent system /nix/store/sgmhnb5fwh3vvd4nx2937ixmlgb9h8mr-nixos-system-nixos-26.11.20260919.20b1ddd, coherent image derivation /nix/store/gqix4f4q4y4bfnwii9bj8mq00822lg8h-k230-sd-image.img.drv, normal image derivation /nix/store/mw0y48wxa3f6piwa416dnyjd7rafahmw-k230-sd-image.img.drv. The two image derivations differ and no image was built. Repeat evaluation from the final integrated revision before recording a candidate for boot.

Current system-matched host build

From clean source 017125c89a1103c0371035f95544a801f41c14e0, evaluation returned the installed test system 48x70… above and coherent image derivation /nix/store/agidgzbcm2hzmvn2gj1ab4d5z2js4qn6-k230-sd-image.img.drv. The exact build command shown above passed. sfdisk found the expected boot start at sector 8192 and size 229376 sectors; all eight named files were extracted with debugfs using the read-only commands above. The full 2,711,429,120-byte image has SHA-256 e95bfe56162fc7a9dd9e4c0301fbeb9c20e44259fa6cd471b923e6feb7357fc7.

The extracted Image byte-matches 48x70…/kernel. The initrd.uimg has U-Boot ramdisk magic 0x27051956, a 64-byte header and a payload that byte-matches 48x70…/initrd. bootargs.txt and the image DTB agree and contain exactly one init= naming 48x70…/init. Decompiled image and source DTBs differ only by the inserted /chosen/bootargs; the three selector files all name k230-tdisplay.dtb. The normal sdImage derivation remains distinct. The structured record carries the exact paths, timestamps, checks and hashes for review.

Compared with the prior 6ed24efb host image, Image, initrd.uimg, OpenSBI and the three selector files have identical hashes; bootargs.txt and the DTB differ. This comparison is between two host images, not with the board’s currently selected boot files. The reserved-board operator must hash the actual /boot files and preserve the previous selection before any file-only update. No SD write, profile update, reboot, physical theme restoration or ordinary-boot result is claimed here.

The host extraction commands were rehearsed read-only on the already built recovery image /nix/store/b384ag314xp1gprqy3i5h7sbsci3fmm0-k230-sd-image.img: sfdisk reported start 8192/size 229376 sectors, all eight named files extracted, and OpenSBI’s wrapped image SHA256 was 9627edbeea9b115d7040beea27cc61b23b6aca61cd502fd7760d7ee179f42c99. That rehearsal validates extraction syntax and the fixed layout only; it does not identify or validate the new coherent image.