Position Log

Persistent station position history across restarts

By default, graywolf keeps station positions in memory only — a restart clears the live map. The position log feature writes station data to a separate SQLite database so the map is populated immediately after a restart. Positions are retained for 30 days and automatically pruned.

Enabling the Position Log

Open Settings → Position Log in the web UI and toggle Enable persistent position log. The database path is shown read-only; it is set by the service manager via the -history-db flag (see below). The change takes effect immediately — no restart required.

The database file is created automatically if it does not exist. This is important for RAM disk setups where the file disappears on every reboot.

Raspberry Pi & SD Card Considerations

SD cards have a limited number of write cycles. The position log writes to SQLite every time a new station packet is decoded — typically a few times per minute on a 1200 baud channel, but potentially more on busy frequencies or when connected to APRS-IS. Over weeks and months, this can shorten the life of an SD card.

Use a RAM disk

The simplest solution is to store the history database on a tmpfs (RAM disk). On systemd-based systems (including Raspberry Pi OS) /run is always a tmpfs, and systemd can manage a per-service subdirectory for you with correct ownership and lifecycle. Point graywolf at /run/graywolf/history.db.

Note that the packaged systemd unit has PrivateTmp=yes, which gives the service a namespaced /tmp that is wiped on every service restart. For that reason /tmp is not a good choice for the history database — use /run/graywolf/ instead.

Configure the database path

The path is passed to graywolf via the -history-db command-line flag. When running under systemd, add a drop-in:

sudo systemctl edit graywolf

This opens an override file. Add:

[Service]
ExecStart=
ExecStart=/usr/bin/graywolf -config /var/lib/graywolf/graywolf.db -history-db /run/graywolf/history.db -tile-cache-dir /var/lib/graywolf/tiles -modem /usr/bin/graywolf-modem -http 0.0.0.0:8080
RuntimeDirectory=graywolf
RuntimeDirectoryMode=0755
RuntimeDirectoryPreserve=yes

RuntimeDirectory=graywolf creates /run/graywolf/ owned by the graywolf user. RuntimeDirectoryPreserve=yes keeps its contents across systemctl restart so the database survives service restarts (it is still cleared on reboot — see below).

The empty ExecStart= line is required to clear the inherited ExecStart before replacing it.

Then reload and restart:

sudo systemctl daemon-reload
sudo systemctl restart graywolf

What happens on reboot?

With a RAM disk, the history database is lost on every reboot. This is expected and harmless — graywolf recreates the database automatically on startup. The map simply starts empty and fills in as stations are heard. On an active frequency the map is typically well-populated within a few minutes.