the agent s6-overlay Container Supervision

When to use this skill

Load this skill when you're working on:

• Adding or removing a static service in the the agent Docker image (something that should be supervised at every container start, like the dashboard)
• Diagnosing why a per-profile gateway isn't starting, restarting, or surviving docker restart
• Understanding why the container's CMD is /opt/hermes/docker/main-wrapper.sh and how leading-dash args reach the user's program
• Modifying cont-init.d boot scripts (UID remap, volume seeding, profile reconciliation)
• Changing the rendered run-script for per-profile gateways (Phase 4)

If you're just running the

Architecture at a glance

/init                                  ← PID 1 (s6-overlay v3.2.3.0)
├── cont-init.d                        ← oneshot setup, runs as root
│   ├── 01-hermes-setup                ← docker/stage2-hook.sh
│   │   ├── UID/GID remap
│   │   ├── chown /opt/data
│   │   ├── chown /opt/data/profiles (every boot)
│   │   ├── seed .env / config.yaml / SOUL.md
│   │   └── skills_sync.py
│   └── 02-reconcile-profiles          ← hermes_cli.container_boot
│       ├── chown /run/service (hermes-writable for runtime register)
│       └── walk $HERMES_HOME/profiles/<name>/gateway_state.json
│           → recreate /run/service/gateway-<name>/
│           → auto-start only those with prior_state == "running"
│
├── s6-rc.d (static services, in /etc/s6-overlay/s6-rc.d/)
│   ├── main-hermes/run                ← exec sleep infinity (no-op slot)
│   └── dashboard/run                  ← if HERMES_DASHBOARD=1, runs `hermes dashboard`
│
├── /run/service (s6-svscan watches; tmpfs)
│   ├── gateway-coder/                 ← runtime-registered per-profile
│   │   ├── type        ("longrun")
│   │   ├── run         ("#!/command/with-contenv sh ... exec s6-setuidgid hermes hermes -p coder gateway run")
│   │   ├── down        (marker — present means "registered but don't auto-start")
│   │   └── log/run     (s6-log → $HERMES_HOME/logs/gateways/coder/current)
│   └── ...
│
└── CMD ("main program")               ← /opt/hermes/docker/main-wrapper.sh
    └── routes user args: bare exec | hermes subcommand | hermes (no args)
        — exec'd by /init with stdin/stdout/stderr inherited (TTY for --tui)

Key files

Why Architecture B (CMD as main program, not s6-supervised)

The original plan (v1–v3) called for main hermes to run as a supervised s6-rc service. Two real s6-overlay v3 mechanics blocked that:

1. cont-init.d scripts receive no CMD args — so the stage2 hook can't parse docker run <image> chat -q "hi" to set HERMES_ARGS for a service run script to consume.
2. `/run/s6/basedir/bin/halt` does NOT propagate the exit code written to /run/s6-linux-init-container-results/exitcode. Containers always exit 143 (SIGTERM) regardless. Confirmed by skarnet (s6 author) in issue #477: _"if you want a container shutdown, you need to either have your CMD exit, or, if you have no CMD, write the container exit code you want then call halt"_.

So we use the s6-overlay-native CMD pattern: ENTRYPOINT ["/init", "/opt/hermes/docker/main-wrapper.sh"]. /init prepends the wrapper to user args automatically — so docker run <image> --version becomes /init main-wrapper.sh --version, and --version doesn't get intercepted by /init's POSIX shell. The wrapper drops to hermes via s6-setuidgid, then exec's the chosen program. The program's exit code becomes the container exit code, exactly matching the pre-s6 tini contract.

Trade-off: main hermes is unsupervised under s6. That exactly matches its behavior under tini (the pre-s6 image). Dashboard supervision is the only new guarantee — and per-profile gateways under /run/service/ get full supervision.

Quick recipes

Verify s6 is PID 1 in a running container

docker exec <c> sh -c 'cat /proc/1/comm; readlink /proc/1/exe'
# Expect: s6-svscan or init / /package/admin/s6/.../s6-svscan

Inspect a profile gateway service

# /command/ isn't on docker-exec PATH — use absolute path
docker exec <c> /command/s6-svstat /run/service/gateway-<name>
# "up (pid …) … seconds"            → running
# "down (exitcode N) … seconds, normally up, want up, …" → s6 wants it up but the process keeps exiting (crash loop)
# "down … normally up, ready …"     → user stopped it

Bring a service up/down manually

docker exec <c> /command/s6-svc -u /run/service/gateway-<name>   # up
docker exec <c> /command/s6-svc -d /run/service/gateway-<name>   # down
docker exec <c> /command/s6-svc -t /run/service/gateway-<name>   # SIGTERM (restart)

Watch the cont-init reconciler log

docker exec <c> tail -n 50 /opt/data/logs/container-boot.log
# 2026-05-21T06:18:05+0000 profile=coder prior_state=running action=started
# 2026-05-21T06:18:05+0000 profile=writer prior_state=stopped action=registered

Add a new static service

1. Create docker/s6-rc.d/<name>/type with longrun\n and docker/s6-rc.d/<name>/run (use #!/command/with-contenv sh + # shellcheck shell=sh).
2. Drop to hermes via s6-setuidgid hermes at the top of run (unless you specifically need root).
3. Create empty docker/s6-rc.d/<name>/dependencies.d/base so it waits for the base bundle.
4. Create empty docker/s6-rc.d/user/contents.d/<name> so it joins the user bundle.
5. The COPY docker/s6-rc.d/ in the Dockerfile picks it up automatically — no other changes.

Change the per-profile gateway run command

Edit S6ServiceManager._render_run_script in hermes_cli/service_manager.py. The function is also called by hermes_cli/container_boot.py::_register_service during boot reconciliation, so it's the single source of truth. Update the corresponding assertion in tests/hermes_cli/test_service_manager.py::test_s6_register_creates_service_dir_and_triggers_scan.

Run the docker test harness

docker build -t 
HERMES_TEST_IMAGE=
# Expect 19 passed, 0 xfailed against the s6 image

The harness lives in tests/docker/ and skips when Docker isn't available. The per-test timeout is bumped to 180s (see tests/docker/conftest.py).

Common pitfalls

"command not found" via docker exec

/command/ (where s6-overlay puts its binaries) is on PATH only for processes spawned by the supervision tree — services, cont-init.d, main-wrapper.sh. docker exec <c> s6-svstat … will fail with "command not found"; always use the absolute path /command/s6-svstat. The hermes binary works because the Dockerfile adds /opt/hermes/.venv/bin to the runtime ENV PATH.

Profile directory ownership

The cont-init reconciler runs as hermes (s6-setuidgid hermes in 02-reconcile-profiles). If a profile dir ends up root-owned (e.g. because docker exec <c> hermes profile create … ran as root by default), the reconciler can't read SOUL.md and fails with PermissionError. Mitigation: stage2-hook.sh chowns $HERMES_HOME/profiles to hermes on every boot, idempotently. Don't remove that block.

Files written by docker exec are root-owned

docker exec defaults to root. Either pass --user hermes or rely on the stage2 chown sweep next reboot. Don't write files under $HERMES_HOME/profiles/<name>/ as root manually — the next reconcile pass will sweep them but in-flight operations may hit perm errors.

Service slot exists but s6-svstat says "s6-supervise not running"

The service directory is on tmpfs and was wiped on container restart. Either the cont-init reconciler hasn't run yet (give it a moment after docker restart) or it failed. Check docker logs <c> | grep '02-reconcile'.

Gateway starts then immediately exits (down (exitcode 1) in svstat)

Most likely the profile has no model or auth configured. The service slot is correct — the gateway itself is unconfigured. Run hermes -p <profile> setup first. The s6 supervisor will keep restarting it; that's the desired behavior (when you fix the config, the next attempt succeeds and stays up).

Reconciler skipped a profile

The reconciler keys on the presence of `SOUL.md` as the "real profile" marker. hermes profile create always seeds it. If a profile dir is missing SOUL.md (stray directory, partial restore, backup-in-progress), the reconciler skips it intentionally. Add a SOUL.md (even empty) to opt back in.

"Help, the container exits 143!"

Check whether something is invoking s6-svscanctl -t or /run/s6/basedir/bin/halt — both cause /init to begin stage 3 shutdown but return 143 (SIGTERM) rather than the desired exit code. This was the Phase 2 architecture pivot from A to B. For container shutdown with a real exit code, you must let the CMD (main-wrapper.sh) exit normally; do not try to control exit from a finish script.

Related skills

• `
• hermes-tool-quirks: Specific the agent-tool workarounds (sed/grep/etc.) — load when debugging the s6 stack's interaction with hermes built-in tools.