utils/vmbox/guest
Krzysztof kuhy Rudnicki cb3c985ee6 vmbox: 3-4x faster runs, a read-only host package cache, and vm scp
`vm run` took 41s cold / 30s warm to run `true`. Both were vmbox waiting on
itself. Now 12s / 0s, with all five shutdown verdicts re-tested unchanged.

- _run_settle waited up to 30s for the kernel's "reboot: Power down" marker
  UNCONDITIONALLY, including on the majority of runs that leave the guest up,
  where that marker is never going to appear. It now settles only when the
  guest has actually stopped, or when ssh returned 255 (what a successful
  poweroff looks like from the host).

- The ssh readiness polls used a 5s ConnectTimeout. QEMU's user-mode
  networking ACCEPTS the forwarded connection while the guest still has
  nothing on :22, so each probe blocked for the full timeout instead of
  failing fast: a guest reachable at ~10s was reported up at ~45s. Fixed in
  both the sandbox and build paths, via an env override -- ssh honours the
  FIRST value for an option, so a second -o could not have worked.

Making runs fast exposed a race: sshd now answers BEFORE tty1's autologin has
started Xorg, so the X environment could be missing on the first run after a
boot. `VMBOX_X_WAIT=<seconds>` waits for the session; it defaults to 0 so an
ordinary run never pays for a graphical session it is not using.

Build: the host's /var/cache/pacman/pkg is offered to the build guest
read-only (`readonly=on` AND an `ro` mount, because it is the real host cache)
as an extra CacheDir after the guest's own writable one, so a package the host
lacks still downloads rather than failing the build. This removes the 396 MiB
the build used to fetch. Host cache verified byte-for-byte identical across
four builds: same file count, same size, same mtime.

Build time itself moved only 103.8s -> 100.3s. Per-phase timings (also added
here) show why: 47s of it is the build guest's cloud-init first boot, and that
is NOT datasource probing -- `cloud-init analyze blame` totals 2.27s. Left
unexplained rather than guessed at; SESSION_RESULTS.md records the evidence.

Also: `vm scp`, which lib/ssh.sh could always do but the CLI never exposed,
and provision.sh split at the 250-line cap.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VdyMBGCrGVGDWtJ9xe48f3
2026-08-22 23:17:21 +02:00
..
dummy-creds.sh vmbox: disposable Arch VM sandbox for destructive system tests 2026-08-22 20:47:56 +02:00
provision-desktop.sh vmbox: 3-4x faster runs, a read-only host package cache, and vm scp 2026-08-22 23:17:21 +02:00
provision.sh vmbox: 3-4x faster runs, a read-only host package cache, and vm scp 2026-08-22 23:17:21 +02:00