kern samples process-tree cpu and ram — a server's children count toward it (node workers, cargo/rustc, a jar's threads). the detail header draws this as the reactor channel: cpu shimmers along the top row, ram fills from the left, both turn amber past 90% and red on fault.

the fleet dashboard shows the same numbers for every instance at once. first sample after a start reads ~0% — sysinfo reports cpu as a delta between reads, so the spin-up settles over the first second.

bash
kern-cli host                       # host cpu/ram
kern-cli top                        # live fleet view
kern-cli metrics "My Server" --spark

a background worker records one sample per instance every 30 seconds into a rolling in-memory ring (about 7 days). the monitor tab graphs 24h / 7d cpu and ram. history is not persisted across restarts — it's telemetry, not a database.

bash
kern-cli metrics "My Server" --window 86400 --spark

per-instance rules fire when a metric stays above a threshold for a sustained window:

configure under monitor → alerts. a fired alert goes to the notification center (and your webhook) once, then re-arms after the value recovers. the alert state is also visible in the tray icon: amber sweep/blips and a tooltip marker.

when a process exits unexpectedly, kern writes the exit code plus the last log lines to <app_data>/crashes/<id>.json and shows a last crash card on the monitor tab.

bash
kern-cli crash "My Server"

if the watchdog is enabled, the restart attempt is recorded too, and a crash-loop backs off exponentially instead of thrashing.

kern matches the instance's process tree against the os socket table and surfaces the ports it actually bound, with a copy-ready connect string.

bash
kern-cli port "Minecraft"           # :25565 → localhost:25565

preflight uses the last-observed ports to warn before a start:

bash
kern-cli preflight "Minecraft"
# ! port 25565 held by javaw.exe (pid 8123)
# ! minecraft eula is pending (edit eula.txt)

with a power price and machine wattage set in settings, kern estimates each instance's running cost (draw scales between an idle baseline and full load):

bash
kern-cli energy "My Server"