Pi 3 simulator boot through Pi OS systemd graph was unworkable inside
QEMU's raspi3b emulation:
* The PL011 UART at 0x3f201000 enumerates as ttyAMA1 (not ttyAMA0 —
the mini-UART at 0x3f215040 takes ttyAMA0 and fails to probe under
QEMU). After ~9 s of kernel time the boot effectively went silent
on the serial: earlycon was disabled by the normal console init
and the IRQ-driven serial driver loses TX under QEMU's emulation.
* Even with `keep_bootcon`, systemd dependency graph took 2-3 min to
walk inside emulation (network waits, tmpfiles, journald,
hostname/machine-id randomness). Masking 9 boot-blocking units
helped but didn't fix the silent-after-9s problem.
Solution: skip systemd. The SD image is now baked with
`/usr/local/sbin/velxio-init` (a 30-line bash script) and the kernel
cmdline points init= at it. velxio-init mounts /proc /sys /dev /pts
/run /tmp, sets hostname, then loops a passwordless `/bin/bash
--login </dev/ttyAMA1 >/dev/ttyAMA1`. User sees the prompt within
~10 s of clicking Run; Ctrl-D respawns a fresh session.
Cmdline additions:
- `keep_bootcon` — keep earlycon alive after the regular console
registers, so kernel printk continues to reach ttyAMA1.
- `console=ttyAMA1,115200` — the correct PL011, not ttyAMA0.
- `init=/usr/local/sbin/velxio-init` — bypass systemd entirely.
Python, GPIO shim, apt, mount, etc. all work — they don't need
systemd as PID 1, just a populated rootfs + mounted pseudo-fs.
Manifest version bumped to 2026-04-21+velxio-init. Same byte size,
different SHA, so the sidecar-based cache invalidator forces a
re-fetch on every velxio backend the next time it starts.
c4b6b8ea69