open-productive-stack/mailcow/data/Dockerfiles/watchdog/check_dns.sh
2026-01-19 13:10:13 +01:00

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#!/bin/sh
while getopts "H:s:" opt; do
case "$opt" in
H) HOST="$OPTARG" ;;
s) SERVER="$OPTARG" ;;
*) echo "Usage: $0 -H host -s server"; exit 3 ;;
esac
done
if [ -z "$SERVER" ]; then
echo "No DNS Server provided"
exit 3
fi
if [ -z "$HOST" ]; then
echo "No host to test provided"
exit 3
fi
# run dig and measure the time it takes to run
START_TIME=$(date +%s%3N)
dig_output=$(dig +short +timeout=2 +tries=1 "$HOST" @"$SERVER" 2>/dev/null)
dig_rc=$?
dig_output_ips=$(echo "$dig_output" | grep -E '^[0-9.]+$' | sort | paste -sd ',' -)
END_TIME=$(date +%s%3N)
ELAPSED_TIME=$((END_TIME - START_TIME))
# validate and perform nagios like output and exit codes
if [ $dig_rc -ne 0 ] || [ -z "$dig_output" ]; then
echo "Domain $HOST was not found by the server"
exit 2
elif [ $dig_rc -eq 0 ]; then
echo "DNS OK: $ELAPSED_TIME ms response time. $HOST returns $dig_output_ips"
exit 0
else
echo "Unknown error"
exit 3
fi