Container Layout

/data
 ├─ config.yaml           # See also configuration reference
 ├─ logs/                 # Rolling logs for agent, every data flow, Redpanda …
 ├─ redpanda/             # Redpanda data & WALs (backup-worthy)
 ├─ services/             # S6 service directories (only when S6_PERSIST_DIRECTORY=true)
 └─ hwid                  # Device fingerprint sent to the console

/tmp/umh-core-services/   # S6 service directories (default, cleared on restart)

/run/service/             # S6 scan directory (contains symlinks to service directories)

Mount one persistent volume (e.g. umh-core-data) to /data and you're done.

/config.yaml

See also Configuration Reference

/logs

File/dir	What it is for	When it appears
current	The file S6 is actively appending log lines to. Keep an eye on this one with tail -f.	Always – it is recreated immediately after every rotation. (Skarnet)
previous	A temporary name used during a rotation; disappears once rotation completes.	Only while a rotation is in flight. (Skarnet)
@<timestamp>.s	An archived log that was rotated cleanly. The timestamp is the moment the rotation occurred.	After every successful rotation. (Skarnet)
@<timestamp>.u	A “unfinished” archive – it was the current file when the container was killed.	Only after an un-clean shutdown. (Skarnet)
lock, state, processed, newstate	Book-keeping files S6-log uses while rotating or while a post-processor runs.	Internal – you normally ignore them. (Skarnet)

The life-cycle in practice

1. Normal running – all services write to their own current file.

2. Size hits 1 MB – S6 atomically renames current to a name such as @20250530T131218Z.s, then immediately creates a fresh empty current. (Skarnet)

3. Prune – if the directory now has > 20 archives, the oldest ones are deleted so the newest 20 remain. (Skarnet)

4. You read logs – use:

   # live stream
   tail -f /data/logs/<service>/current
   
   # inspect an old file (the '@…s' ones are plain text)
   less /data/logs/<service>/@20250530T131218Z.

/redpanda

The Redpanda data directory.

HWID

A unique identifier for that UMH Core installation. Useful for troubleshooting.

S6 Service Directories

UMH Core uses S6 overlay for service supervision. Service directories contain the runtime state and configuration for each managed service (Benthos, Redpanda, monitors, etc.).

By default, these directories are created in /tmp/umh-core-services/ which is cleared on container restart, ensuring a clean state. This prevents issues from stale supervisor state files.

For debugging purposes, you can set S6_PERSIST_DIRECTORY=true to use /data/services/ instead, which persists across container restarts. This allows inspection of S6 supervisor state files when troubleshooting service startup issues.

The /run/service/ directory contains symlinks pointing to the actual service directories, which S6's scanner monitors for changes.

See the Environment Variables reference for more details on S6_PERSIST_DIRECTORY.