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Dynamic DNS Script for Route53
#!/bin/bash
# (optional) You might need to set your PATH variable at the top here
# depending on how you run this script
#PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
# Hosted Zone ID e.g. BJBK35SKMM9OE
ZONEID="XXXXXXXXX"
# The CNAME you want to update e.g. hello.example.com
RECORDSET="XXXX.YYYYY.com"
# More advanced options below
# The Time-To-Live of this recordset
TTL=300
# Change this if you want
COMMENT="Auto updating @ `date`"
# Change to AAAA if using an IPv6 address
TYPE="A"
# Get the external IP address from OpenDNS (more reliable than other providers)
IP=`dig +short myip.opendns.com @resolver1.opendns.com`
function valid_ip()
{
local ip=$1
local stat=1
if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
OIFS=$IFS
IFS='.'
ip=($ip)
IFS=$OIFS
[[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
&& ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
stat=$?
fi
return $stat
}
# Get current dir
# (from http://stackoverflow.com/a/246128/920350)
DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
LOGFILE="$DIR/route53-dyndns.log"
IPFILE="$DIR/route53-dyndns.ip"
if ! valid_ip $IP; then
echo "Invalid IP address: $IP" >> "$LOGFILE"
exit 1
fi
# Check if the IP has changed
if [ ! -f "$IPFILE" ]
then
touch "$IPFILE"
fi
if grep -Fxq "$IP" "$IPFILE"; then
# code if found
echo "IP is still $IP. Exiting" >> "$LOGFILE"
exit 0
else
echo "IP has changed to $IP" >> "$LOGFILE"
# Fill a temp file with valid JSON
TMPFILE=$(mktemp /tmp/temporary-file.XXXXXXXX)
cat > ${TMPFILE} << EOF
{
"Comment":"$COMMENT",
"Changes":[
{
"Action":"UPSERT",
"ResourceRecordSet":{
"ResourceRecords":[
{
"Value":"$IP"
}
],
"Name":"$RECORDSET",
"Type":"$TYPE",
"TTL":$TTL
}
}
]
}
EOF
echo $TMPFILE
# Update the Hosted Zone record
aws route53 change-resource-record-sets \
--hosted-zone-id $ZONEID \
--change-batch file://"$TMPFILE" >> "$LOGFILE"
echo "" >> "$LOGFILE"
# Clean up
echo $TMPFILE
# rm $TMPFILE
fi
# All Done - cache the IP address for next time
echo "$IP" > "$IPFILE"
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