| name | managing-watchtower |
| description | Use when working with Watchtower — watchtower container update automation
analysis covering monitored container inventory, update schedules,
notification configuration, update history, container labeling for inclusion
and exclusion, and rolling restart policies. Use for auditing automated
container update infrastructure.
|
| connection_type | watchtower |
| preload | false |
Watchtower Management
Analyze Watchtower automated container update configuration and update history.
Phase 1: Discovery
#!/bin/bash
DOCKER_CMD="${DOCKER_CMD:-docker}"
echo "=== Watchtower Container ==="
$DOCKER_CMD inspect watchtower 2>/dev/null | jq '.[0] | {
id: .Id[0:12],
image: .Config.Image,
state: .State.Status,
started: .State.StartedAt,
env: [.Config.Env[] | select(startswith("WATCHTOWER_"))]
}'
echo ""
echo "=== Watchtower Schedule ==="
$DOCKER_CMD inspect watchtower 2>/dev/null | jq -r '.[0].Config.Env[] | select(startswith("WATCHTOWER_SCHEDULE") or startswith("WATCHTOWER_POLL_INTERVAL"))' 2>/dev/null
POLL=$($DOCKER_CMD inspect watchtower 2>/dev/null | jq -r '.[0].Config.Env[] | select(startswith("WATCHTOWER_POLL_INTERVAL")) | split("=") | last' 2>/dev/null)
[ -n "$POLL" ] && echo "Poll interval: ${POLL}s ($(echo "$POLL / 3600" | bc)h)"
echo ""
echo "=== Monitored Containers ==="
$DOCKER_CMD ps --format '{{.Names}}\t{{.Image}}\t{{.Status}}' | while IFS=$'\t' read NAME IMAGE STATUS; do
LABEL=$($DOCKER_CMD inspect "$NAME" 2>/dev/null | jq -r '.[0].Config.Labels["com.centurylinklabs.watchtower.enable"] // "default"')
echo -e "${NAME}\t${IMAGE}\t${LABEL}\t${STATUS}"
done | column -t | head -20
echo ""
echo "=== Excluded Containers ==="
$DOCKER_CMD ps -a --format '{{.Names}}' | while read NAME; do
LABEL=$($DOCKER_CMD inspect "$NAME" 2>/dev/null | jq -r '.[0].Config.Labels["com.centurylinklabs.watchtower.enable"] // "default"')
[ "$LABEL" = "false" ] && echo "$NAME"
done
echo ""
echo "=== Notification Config ==="
$DOCKER_CMD inspect watchtower 2>/dev/null | jq -r '.[0].Config.Env[] | select(startswith("WATCHTOWER_NOTIFICATION"))' 2>/dev/null | sed 's/=.*TOKEN.*/=<REDACTED>/' | sed 's/=.*URL.*/=<REDACTED>/'
Phase 2: Analysis
#!/bin/bash
DOCKER_CMD="${DOCKER_CMD:-docker}"
echo "=== Watchtower Logs (recent updates) ==="
$DOCKER_CMD logs watchtower --tail 100 2>&1 \
| grep -E "Found new|Updating|Stopping|Starting|Unable" | tail -20
echo ""
echo "=== Update Summary ==="
UPDATED=$($DOCKER_CMD logs watchtower --tail 500 2>&1 | grep -c "Found new" 2>/dev/null)
FAILED=$($DOCKER_CMD logs watchtower --tail 500 2>&1 | grep -c "Unable to update" 2>/dev/null)
echo "Recent updates: ${UPDATED:-0} successful, ${FAILED:-0} failed"
echo ""
echo "=== Container Image Freshness ==="
$DOCKER_CMD ps --format '{{.Names}}\t{{.Image}}\t{{.CreatedAt}}' | while IFS=$'\t' read NAME IMAGE CREATED; do
DIGEST=$($DOCKER_CMD inspect "$NAME" 2>/dev/null | jq -r '.[0].Image[0:19]')
echo -e "${NAME}\t${IMAGE}\t${CREATED}\t${DIGEST}"
done | column -t | head -20
echo ""
echo "=== Watchtower Configuration Flags ==="
inspect watchtower 2>/dev/null | jq
logs watchtower -- 200 2>&1 \
| grep -E | -10
Output Format
WATCHTOWER ANALYSIS
====================
Container Image Watched Last Updated Status
────────────────────────────────────────────────────────────────────────
nginx-proxy jwilder/nginx-proxy yes 2h ago running
app-web myapp:latest yes 1d ago running
postgres-db postgres:15 no manual running
Schedule: Every 6h (POLL_INTERVAL=21600)
Mode: Update (not monitor-only) | Cleanup: enabled | Rolling: disabled
Recent: 5 updates, 0 failures | Notifications: slack
Safety Rules
- Read-only: Only use
docker inspect, docker ps, and docker logs
- Never modify Watchtower configuration or restart containers without confirmation
- Notifications: Redact webhook URLs and tokens from notification config
- Log limits: Always use
--tail to prevent unbounded log output
Anti-Hallucination Rules
- NEVER assume resource names — always discover via CLI/API in Phase 1 before referencing in Phase 2.
- NEVER fabricate metric names or dimensions — verify against the service documentation or
--help output.
- NEVER mix CLI commands between service versions — confirm which version/API you are targeting.
- ALWAYS use the discovery → verify → analyze chain — every resource referenced must have been discovered first.
- ALWAYS handle empty results gracefully — an empty response is valid data, not an error to retry.
Counter-Rationalizations
| Shortcut | Counter | Why |
|---|
| "I'll skip discovery and check known resources" | Always run Phase 1 discovery first | Resource names change, new resources appear — assumed names cause errors |
| "The user only asked for a quick check" | Follow the full discovery → analysis flow | Quick checks miss critical issues; structured analysis catches silent failures |
| "Default configuration is probably fine" | Audit configuration explicitly | Defaults often leave logging, security, and optimization features disabled |
| "Metrics aren't needed for this" | Always check relevant metrics when available | API/CLI responses show current state; metrics reveal trends and intermittent issues |
| "I don't have access to that" | Try the command and report the actual error | Assumed permission failures prevent useful investigation; actual errors are informative |
