.

Dockerfile

@@ -0,0 +1,11 @@
+FROM alpine:latest
+
+RUN apk add --no-cache iputils coreutils tzdata
+
+ENV TZ=Europe/Rome
+
+WORKDIR /app
+COPY check.sh .
+RUN chmod +x check.sh
+
+CMD ["./check.sh"]

check.sh

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+#!/bin/sh
+
+HOST="${HOST_TO_CHECK:-example.com}"
+INTERVAL="${INTERVAL_SECONDS:-300}"
+LOGFILE="/logs/${HOST}.log"
+
+mkdir -p /logs
+
+echo "Monitoring $HOST every $INTERVAL seconds..."
+
+while true; do
+  OUTPUT=$(ping -c 1 -W 2 "$HOST" 2>&1)
+  EXIT_CODE=$?
+
+  if [ $EXIT_CODE -ne 0 ]; then
+    TIMESTAMP=$(date '+%Y-%m-%d %H:%M:%S')
+
+    if echo "$OUTPUT" | grep -q "bad address"; then
+      REASON="DNS resolution failed"
+    elif echo "$OUTPUT" | grep -q "Network is unreachable"; then
+      REASON="No route to network"
+    elif echo "$OUTPUT" | grep -q "ping: permission denied"; then
+      REASON="ICMP not permitted (try running as root or with CAP_NET_RAW)"
+    elif echo "$OUTPUT" | grep -q "100% packet loss"; then
+      REASON="Timed out (no response)"
+    else
+      REASON="Unknown error: $OUTPUT"
+    fi
+
+    echo "[$TIMESTAMP] Host unreachable: $HOST — Reason: $REASON" | tee -a "$LOGFILE"
+  fi
+
+  sleep "$INTERVAL"
+done

docker-compose.yml

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+services:
+  host-checker:
+    build: .
+    environment:
+      - HOST_TO_CHECK=psql01.poloinformatico.it
+      - INTERVAL_SECONDS=120
+    volumes:
+      - ./logs:/logs
+    restart: always