bot-bottle/docs/research/testing-clean-install-on-linux.md

# Testing a clean bot-bottle install on Linux

How do you exercise `install.sh` the way a brand-new user would — on a
pristine Linux environment you can throw away afterward — *without*
polluting your daily-driver host, and across the several package-management
regimes Linux fragments into? This is the Linux counterpart to
[`testing-clean-install-on-macos.md`](testing-clean-install-on-macos.md);
the conclusion is different because Linux gives us a boundary macOS doesn't.

## Summary

On macOS the honest options were a throwaway user or a VM, and the throwaway
user won on pragmatics (nested virtualization is gated to M3+). On Linux the
calculus flips: a **disposable KVM virtual machine, booted from a distro
cloud image and deleted per run, is both the cleanest boundary and the one
that lets a single harness cover Ubuntu, Fedora, Arch, Alpine, and NixOS**.
The host already requires KVM for the Firecracker backend, so the VM is cheap
here.

The harness lives at [`scripts/linux-install-test.sh`](../../scripts/linux-install-test.sh).
Per run it caches one read-only base image, boots a throwaway copy-on-write
overlay (`qemu-img create -b base`), installs the distro's prerequisites,
pipes *this checkout's* `install.sh` into the guest exactly as `curl … | sh`
would, asserts the CLI installed, and deletes the overlay — the Linux
equivalent of `docker run --rm`, for a whole machine.

## Why a VM, not a container or a throwaway user

| Mechanism | Why it's the wrong boundary here |
|---|---|
| **Container** (`docker run --rm`) | Shares the host kernel and ships a deliberately minimal userland — no systemd, a stubbed-out package manager story, and (crucially) it doesn't reproduce the *externally-managed Python* (PEP 668) that real desktop/server installs put in front of the user. It tests "does install.sh run in a container," not "does it run on a real distro." |
| **Throwaway user** (`useradd`/`userdel`) | The macOS pick, but weaker on Linux: it reaches the real host, yet every system package it installs (python, pipx, git via `apt`/`dnf`/…) stays behind, and it can only ever test the *one* distro the host runs. The whole Linux-specific value is the cross-distro matrix. |
| **Disposable KVM VM** (this harness) | A genuine kernel + userland + package-manager boundary that wipes to nothing on teardown, and swaps freely between distro cloud images. The one real cost — nested virtualization for the *backend* — doesn't apply, because we gate the installer, not the runtime (below). |

## Two variants: `test` (bare host) and `test-ready` (prepared host)

`install.sh` never installs a backend, and never installs its own toolchain
prerequisites (python3, git, pipx) — it installs the `bot-bottle` package and
runs `doctor`, which *reports* what's missing
([`install.sh`](../../install.sh) header,
[`bot_bottle/cli/commands/doctor.py`](../../bot_bottle/cli/commands/doctor.py)).
That leaves two distinct things worth testing, split into two subcommands that
mirror the macOS harness's `test` / `test-ready` convention (there the split is
the backend service; here it is the toolchain the installer needs):

- **`test`** — `install.sh` runs on the **bare cloud image**, prerequisites and
  all left as the vendor ships them. This exercises `install.sh`'s own
  prerequisite-guard logic — the entire first half of the script (python
  version gate, git-for-git-specs gate, pipx/pip PEP-668 handling).
- **`test-ready`** — the harness installs python3 + git + pipx first (the
  `prereqs` step), then runs `install.sh`. This is the *prepared-host happy
  path*: does a clean install actually land and produce a working CLI?

**Pass criteria differ by variant:**

| Variant | PASS when |
|---|---|
| `test` | `install.sh` **either** installs cleanly (the image already carried enough) **or** declines with one of its own recognized, actionable prerequisite errors (missing python3/git, no usable pip, PEP 668). A crash or an *unrecognized* failure is a FAIL. |
| `test-ready` | `install.sh` actually lands: the `bot-bottle` entry point is present and runs, and `doctor` reports a usable python and config without crashing. A graceful decline is no longer good enough. |

Neither variant requires a green `doctor`: inside the VM there is no nested KVM
or Docker, so **the backend is correctly reported not-ready** — install.sh does
not install a backend and cannot regress one, and this harness does not
provision the Docker backend. This is where Linux necessarily diverges from the
macOS `test-ready`, which reaches the host backend; `BB_TEST_REQUIRE_BACKEND=1`
makes readiness fatal anyway, for a nested-virt host that can satisfy it. The
verdict instead classifies `doctor`'s output the way the macOS harness does — a
`Traceback` is an install defect (fail), a missing `python`/`config` line is a
fail, a not-ready backend is reported — so a genuine installer regression (a
broken shim, an import error, a botched PATH) stays visible.

`test-all` runs the full matrix — every distro × both variants — each cell in
its own throwaway VM, and prints a per-cell PASS/FAIL summary.

## The distro matrix is the point

Each distro exercises a different corner of the installer:

| Distro | Cloud image | What it stresses |
|---|---|---|
| **Ubuntu** (noble) | `cloud-images.ubuntu.com` | The common case; `apt`'s `pipx`, externally-managed Python (PEP 668) → install.sh's pipx path. |
| **Fedora** | Fedora Cloud Base Generic | `dnf` packaging, a different default Python, BSD-style checksum file. |
| **Arch** | `geo.mirror.pkgbuild.com/images/latest` | Rolling / newest Python; `python-pipx`. |
| **Alpine** | Alpine `nocloud_` (cloudinit) image | musl libc + BusyBox `sh` — the harshest POSIX-`sh` host for a `#!/bin/sh` installer. |
| **NixOS** | locally built with `nixos-generators` | No FHS `~/.local` on PATH by default; `nix profile install` prereqs; pipx laying a self-contained venv on a non-FHS host. |

### Validation run (2026-07-27) — full green

Full matrix on the delphi KVM host, QEMU 11.0.2, both variants × all five
distros passing:

| Distro | `test` (bare) | `test-ready` (prepared) |
|---|---|---|
| Ubuntu 24.04 | ✅ declines at git gate | ✅ installs, doctor python+config green |
| Fedora 44 | ✅ declines at git gate | ✅ installs |
| Arch (latest) | ✅ declines at git gate | ✅ installs |
| Alpine 3.21 | ✅ declines at git gate | ✅ installs |
| NixOS 24.11 | ✅ declines (no python3) | ✅ installs |

The bare `test` sees `install.sh` decline soundly — exit 1 at the
git-for-git-specs gate on the Debian/Fedora/Arch/Alpine images (they ship
python3 but not git), and at the python3 gate on NixOS (no python3 on PATH) —
and `test-ready` installs cleanly with `doctor` reporting a usable python and
config (backends all not-ready, as expected in a plain VM).

Getting to green surfaced and fixed a series of real defects:

- **Fedora 41 was EOL/404** → bumped to 44.
- The liveness probe used `bot-bottle --version`, which the CLI does not
  implement (unknown args die non-zero), so every *successful* install was
  misreported as failed → switched to `bot-bottle --help`.
- **Alpine** needed three fixes: the `generic_` image ignores a NoCloud seed
  (switched to the `nocloud_` variant); OpenRC does not auto-start sshd after
  cloud-init injects the key (start it via `runcmd`); and Alpine's non-PAM
  sshd refuses pubkey auth for a cloud-init-*locked* account (give it a
  throwaway password). It also has no `sudo` by default (install it via
  cloud-init `packages:`).
- **NixOS** publishes no downloadable cloud qcow2 (its cloud images are
  Hydra-built AMIs), so the harness builds one with `nixos-generators`
  ([`linux-install-test-nixos.nix`](../../scripts/linux-install-test-nixos.nix)):
  cloud-init for the key, flakes enabled, deliberately no python/git/pipx. The
  `test-ready` prereq install pins `nixpkgs/nixos-24.11` because the guest's
  default unstable registry builds pipx from source (and its test suite
  currently fails to build).
- Two harness-hygiene bugs also fixed: `cmd_down` left `serial.log` behind
  (orphaned run dirs), and the teardown trap was armed after `cmd_up`, leaking
  a VM when `wait_for_ssh` timed out.

In `test-ready` the harness installs `python3 + git + pipx` first on each
distro (install.sh installs none of them), so all five drive the recommended
pipx path. `test` then removes that scaffolding and lets each distro's bare
image collide with install.sh's guards — on most cloud images python3 is
present (cloud-init needs it) but git and pipx are not, so install.sh is
expected to decline at the git-for-git-specs gate or the PEP-668 pip check with
an actionable message. Both are legitimate, and the two variants together cover
the whole first half of the installer as well as the happy path.

## What a clean install touches (the footprint that decides "wipeable")

| Artifact | Location | In the guest's `$HOME`? | Survives VM teardown? |
|---|---|---|---|
| Config / state / db | `~/.bot-bottle/{agents,bottles,contrib,…}` ([`install.sh`](../../install.sh)) | ✅ | ❌ overlay deleted |
| pipx venv + shim | `~/.local/pipx/venvs/bot-bottle`, shim in `~/.local/bin` | ✅ | ❌ overlay deleted |
| pip `--user` fallback | `~/.local/lib` + `~/.local/bin` | ✅ | ❌ overlay deleted |
| **Distro prerequisites** (python/git/pipx, `test-ready` only) | system paths via `apt`/`dnf`/`pacman`/`apk`/`nix profile` | ❌ | ❌ **overlay deleted** |

Unlike the macOS throwaway user (whose Homebrew / Apple-Container / Rosetta
footprint *survives*), **every row here dies with the overlay** — that is the
VM's whole advantage. The cached base image is read-only backing and is the
only thing that persists between runs, on purpose.

## Design notes baked into the harness

- **User-mode networking** (`-netdev user,hostfwd=tcp:127.0.0.1:PORT-:22`):
  no root, no bridge, no host network state touched. Only SSH is forwarded.
- **cloud-init seed ISO** (`cloud-localds`) injects an ephemeral SSH keypair
  and a passwordless-sudo login. The keypair is generated per run and deleted
  on teardown; the guest can't be logged into after it's gone.
- **Copy-on-write overlay**: the cached base is never mutated, so a corrupt or
  interrupted run can't poison the cache; downloads land at `*.partial` and
  are renamed only after checksum verification.
- **Checksums**: verified against each vendor's published sums file at
  download time (GNU `hash  file`, bare-hash, and Fedora's BSD
  `SHA256 (file) = hash` formats are all handled). Alpine ships `.sha512` only
  (this verifier is sha256) so it is skipped; NixOS is built locally, not
  downloaded, so there is nothing to verify.
- **NixOS is built, not downloaded**: `ensure_base_image` runs
  `nixos-generate -f qcow` against
  [`linux-install-test-nixos.nix`](../../scripts/linux-install-test-nixos.nix)
  once and caches the result; the per-run seed/overlay flow is otherwise
  identical to the downloaded distros.
- **`test-all`** runs every distro × both variants (`test` and `test-ready`),
  each cell in its own subshell on its own forwarded port, so one cell's
  failure (or teardown trap) can't abort the matrix; it prints a per-cell
  PASS/FAIL summary.

## Not wired into PR CI

Like the macOS harness, the runtime is host-specific (needs `/dev/kvm`,
`qemu`, and `cloud-localds`) and is not exercised by the Linux pull-request
runner. It is validated statically (`bash -n`, `shellcheck`) and run by hand
on a KVM-capable host. The cloud-image URLs in the `DISTRO` table are the one
place to bump when a distro cuts a newer build.