docs: write the three missing app-developer docs (secrets, quadlet, lifecycle)
The open-source plan flagged three references as "the real gaps for app developers", and the docs index named them as not-yet-written. Written now, each from the code rather than stubbed: - secrets.md — generated_secrets/secret_env: the two halves, the four kinds (hex16/hex32/base64/bcrypt) and which files each writes, the idempotent self-healing 0600 materialisation, and the rules a developer must not break (no hardcoded fallbacks, one canonical name, right encoding). From container/secrets.rs and the manifest schema. - quadlet-compilation.md — manifest -> .container unit: the full directive mapping (including Secret= by reference, never value, and Pull=never), where units land (~/.config/containers/systemd, systemctl --user), the render/write/enable/disable lifecycle with write-if-changed, and how to inspect one. From container/quadlet.rs, scoped accurately to the companion-UI path it drives today. - container-lifecycle.md — the level-triggered 30s reconciler: desired state from user-stopped/user-uninstalled/manifest set, the operations table, the self-heal-vs-respect-a-deliberate-stop rule, and migrations-never-destroy-data. From prod_orchestrator.rs and boot_reconciler.rs. Index updated to link all three under App development and the "known gap" note removed. Every link across the docs tree resolves. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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archipelago
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Claude Opus 5
Claude Opus 5
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# Manifest → Quadlet unit
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How an app manifest becomes a Podman [Quadlet](https://docs.podman.io/en/latest/markdown/podman-systemd.unit.5.html)
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`.container` unit that systemd owns, where the unit lands, and how to inspect one.
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Source of truth: `core/archipelago/src/container/quadlet.rs`.
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## Why Quadlet
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Containers used to be fire-and-forget `tokio::spawn` blocks. If the daemon
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crashed mid-spawn or the kernel reaped a parent cgroup, the container vanished
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from `podman ps` and only a manual `podman run` brought it back. Quadlet removes
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that whole class of failure: the unit lives on disk, **systemd owns
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start/restart, and archipelago is just the provisioner**. This is the path that
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runs the companion UI containers today (`archy-bitcoin-ui`, `archy-lnd-ui`,
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`archy-electrs-ui`), and the validated path being flipped to default for apps.
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## What gets generated
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`Quadlet::from_manifest(manifest, name)` translates a manifest into a unit, and
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`render()` produces the file. Every unit carries a header making clear it is not
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hand-edited:
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```ini
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# Generated by archipelago. DO NOT EDIT.
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# Edits are overwritten on the next reconcile.
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[Unit]
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Description=<app description>
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After=network-online.target
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Wants=network-online.target
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Requires=<dependency>.service # one per declared dependency
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After=<dependency>.service
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[Container]
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ContainerName=<name>
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Image=<image ref>
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Pull=never # image must be present locally already
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Network=<host | pasta | slirp4netns | bridge name>
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User=<uid> # when the manifest pins one
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DropCapability=ALL # security default
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AddCapability=<cap> # only capabilities the manifest opts into
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PublishPort=<bind>:<host>:<container>/<proto>
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Environment=<KEY>=<value> # non-secret env only
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Secret=<secret_name>,type=env,target=<KEY> # secrets by REFERENCE, never value
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Volume=<source>:<target><opts>
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ReadOnly=true # when security.readonly_root
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NoNewPrivileges=true # when security.no_new_privileges
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HealthCmd=<cmd> # from the health_check block
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[Service]
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TimeoutStartSec=0
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Restart=<always | on-failure> # from the restart policy
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RestartSec=10 # 10s backoff caps a crash loop
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[Install]
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WantedBy=default.target
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```
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Two things to note in that mapping:
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- **Secrets go in by reference, never by value.** A `secret_env` entry renders as
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`Secret=<name>,type=env,target=<KEY>`, so podman injects the value at run time
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from the node's secret store. The plaintext never appears in the unit file. See
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[App secrets](secrets.md).
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- **`Pull=never` is deliberate.** The provisioner does not pull images from here;
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the image must already be local (pre-pulled or built). A missing image surfaces
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immediately instead of retrying silently behind systemd's restart loop.
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## Where units land
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Rootless, per-user, under the archipelago service user (uid 1000, with linger
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enabled so the units run without an active login):
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```
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~/.config/containers/systemd/<name>.container
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```
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Quadlet's systemd generator translates `<name>.container` into a
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`<name>.service` unit at **daemon-reload** time. Everything is `systemctl --user`
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— the system bus is never touched from this path.
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## Lifecycle: render → write → enable → disable
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The module does four things and nothing else:
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1. **render** — manifest → unit text (above).
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2. **write** — `tempfile + rename` so a partially-written unit is never visible to
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systemd, and `write_if_changed` compares bytes first: if the rendered unit
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matches what is on disk, nothing is touched — no daemon-reload, no restart
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cascade. This is what makes a reconcile tick cheap and non-disruptive.
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3. **enable** — `daemon-reload` then start the `.service`.
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4. **disable** — stop and remove.
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## Inspecting a unit
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Run these **as the archipelago service user** (the units are in its user bus):
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```bash
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# the generated unit
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cat ~/.config/containers/systemd/archy-bitcoin-ui.container
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# what systemd made of it
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systemctl --user cat archy-bitcoin-ui.service
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systemctl --user status archy-bitcoin-ui.service
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journalctl --user -u archy-bitcoin-ui.service
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# after editing a unit by hand for debugging (it will be overwritten on reconcile)
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systemctl --user daemon-reload
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```
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Because the unit is regenerated on every reconcile, the way to change a
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container's shape is to change its **manifest** (and, for a catalog-covered app,
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regenerate and re-sign the catalog), never to edit the `.container` file — the
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`DO NOT EDIT` header is literal.
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## Related
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- [Container lifecycle](container-lifecycle.md) — the reconciler that drives this
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- [App Manifest Specification](app-manifest-spec.md) — the manifest fields mapped above
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- [App secrets](secrets.md) — how `Secret=` references resolve
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- [ADR-001: Podman over Docker](adr/001-podman-over-docker.md)
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