Linode dynamic dns on ubiquiti edge router

linode-ddns.sh

#!/bin/bash

# See https://gist.github.com/zsimic/c39dd9686c6d6b0d149a67ff23286b99 for docs on how to use

# Note: you can invoke with LOGFILE= for troubleshooting
[ -z "$LOGFILE" ] && LOGFILE=/var/log/messages
if [ -z "$1" -a -f $LOGFILE ]; then  # Pass any command line arg to avoid the logging redirect
    exec $0 run 1>> $LOGFILE 2>&1
fi

function do_log {
    echo "$(date +'%h %e %T') $(hostname) linode-ddns: $@"
}

function usage {
    do_log "Usage error: $@"
    exit 1
}

# Note: you can invoke with CFGFILE= for troubleshooting
[ -z "$CFGFILE" ] && CFGFILE=~/.ssh/linode-ddns-cfg.sh
CFGFOLDER=$(dirname $CFGFILE)
IPFILE="$CFGFOLDER/.last-ip"  # Allows to do nothing when IP didn't change, remove file to force re-run

[ ! -f $CFGFILE ] && usage "Config file $CFGFILE does not exist"
source $CFGFILE
[ -z "$TOKEN" ] && usage "TOKEN not defined in $CFGFILE"
[ -z "$RECORDS" ] && usage "RECORDS not defined in $CFGFILE"

URL="https://api.linode.com/v4"
H1="Content-type: application/json"
H2="Authorization: Bearer $TOKEN"
CURRENT_IP=$(ip address show eth0 | grep -Eo 'inet [0-9\.]+' | cut -d " " -f2)
LAST_IP=$([ -f $IPFILE ] && head -1 $IPFILE)

[[ $LAST_IP == $CURRENT_IP ]] && exit 0

DBG=""
[ ! -d /config/scripts ] && DBG="echo"  # Useful to debug, allows to perform actual REST call only on router

for record in $RECORDS; do
    OUTPUT=$($DBG curl -s -H"$H1" -H"$H2" "$@" -XPUT $URL/domains/$record -d "{\"target\": \"$CURRENT_IP\"}")
    if [ $? -ne 0 ]; then
        do_log "Updating record $record failed: $OUTPUT"
        exit 1
    fi
done

do_log "Home IP updated to $CURRENT_IP"
[ ! -f $IPFILE ] && touch $IPFILE && chmod 0600 $IPFILE  # chmod just because domainId is logged there...
echo $CURRENT_IP > $IPFILE
echo "# Updated on $(date) for $RECORDS" >> $IPFILE

Awesome! Thank you :)
I'm not super familiar with ipv6 yet, I thought this wasn't needed with ipv6 :)
Ie, addresses are so plentiful that they can be trivially static...

Routers may be intentionally configured to change their ipv6 every now and then, but that's more to avoid tracking (ie: for privacy reasons), so this addition could play well into that.

I recently upgraded to a UCG-MAX to get 2.5GB internet and had to make a few tweaks to get the script to work on it. As Linode is not supported on these 'Dream' machines as a DDNS provider. The big tweaks are WAN_PORT & SCRIPT_DIR variables since the edge router paths are not there. Also note that the path to the cfg file had to be absolute. /root/.ssh/linode-ddns-cfg.sh.

A critical tweak was adding a space after the -H for the curl headers: curl -s -H "$H1" -H "$H2" "$@" ... not sure why this was needed but this was part of way got it all working.

Verified on UGC-MAX running UNIFI OS 4.4.9

#!/bin/bash

# See https://gist.github.com/zsimic/c39dd9686c6d6b0d149a67ff23286b99 for docs on how to use

#2026-01-02 update variable for WAN port bc some dream devices have flexible wans with default of last port instead of port zero
# other updates for dream devices as tested on ucg-max

WAN_PORT='eth4';
SCRIPT_DIR='/opt/scripts/linode-ddns';

# edge routers usually used port zero for WAN
# uncomment these as needed
#WAN_PORT='eth0';
#SCRIPT_DIR='/config/scripts';

# Note: you can invoke with LOGFILE= for troubleshooting
[ -z "$LOGFILE" ] && LOGFILE=/var/log/messages
if [ -z "$1" -a -f $LOGFILE ]; then  # Pass any command line arg to avoid the logging redirect
    exec $0 run 1>> $LOGFILE 2>&1
fi

function do_log {
    echo "$(date +'%h %e %T') $(hostname) linode-ddns: $@"
}

function usage {
    do_log "Usage error: $@"
    exit 1
}

# Note: you can invoke with CFGFILE= for troubleshooting
[ -z "$CFGFILE" ] && CFGFILE=/root/.ssh/linode-ddns-cfg.sh
CFGFOLDER=$(dirname $CFGFILE)
IPFILE="$CFGFOLDER/.last-ip"  # Allows to do nothing when IP didn't change, remove file to force re-run
IPFILE6="$CFGFOLDER/.last-ip6"  # Allows to do nothing when IP didn't change, remove file to force re-run

[ ! -f $CFGFILE ] && usage "Config file $CFGFILE does not exist"
source $CFGFILE
[ -z "$TOKEN" ] && usage "TOKEN not defined in $CFGFILE"
[ -z "$RECORDS" ] && usage "RECORDS not defined in $CFGFILE"
[ -z "$RECORDS6" ] && usage "RECORDS6 not defined in $CFGFILE"

URL="https://api.linode.com/v4"
H1="Content-type: application/json"
H2="Authorization: Bearer $TOKEN"
CURRENT_IP=$(ip address show "$WAN_PORT" | grep -Eo 'inet [0-9\.]+' | cut -d " " -f2)
CURRENT_IP6=$(ip address show "$WAN_PORT" | grep -Eo 'inet6 [0-9a-f\:]+' | cut -d " " -f2 | head -1)

LAST_IP=$([ -f $IPFILE ] && head -1 $IPFILE)
LAST_IP6=$([ -f $IPFILE6 ] && head -1 $IPFILE6)

[[ $LAST_IP == $CURRENT_IP && $LAST_IP6 == $CURRENT_IP6 ]] && exit 0

DBG=""
[ ! -d "$SCRIPT_DIR" ] && DBG="echo"  # Useful to debug, allows to perform actual REST call only on router
if [[ $LAST_IP != $CURRENT_IP ]]; then
	for record in $RECORDS; do
		OUTPUT=$($DBG curl -s -H "$H1" -H "$H2" "$@" -XPUT $URL/domains/$record -d "{\"target\": \"$CURRENT_IP\"}")
		if [ $? -ne 0 ]; then
			do_log "Updating record $record failed: $OUTPUT"
			exit 1
		fi
	done
fi

if [[ $LAST_IP6 != $CURRENT_IP6 ]]; then
	for record in $RECORDS6; do
		OUTPUT=$($DBG curl -s -H "$H1" -H "$H2" "$@" -XPUT $URL/domains/$record -d "{\"target\": \"$CURRENT_IP6\"}")
		if [ $? -ne 0 ]; then
			do_log "Updating record $record failed: $OUTPUT"
			exit 1
		fi
	done
fi


do_log "Home IP updated to $CURRENT_IP $CURRENT_IP6"
[ ! -f $IPFILE ] && touch $IPFILE && chmod 0600 $IPFILE  # chmod just because domainId is logged there...
echo $CURRENT_IP > $IPFILE
echo "# Updated on $(date) for $RECORDS" >> $IPFILE

#IP6 Version
[ ! -f $IPFILE6 ] && touch $IPFILE6 && chmod 0600 $IPFILE6  # chmod just because domainId is logged there...
echo $CURRENT_IP6 > $IPFILE6
echo "# Updated on $(date) for $RECORDS6" >> $IPFILE6

I've moved away from ubiquiti edge routers 😊 I'm using their "dream machine" now and don't want to publicize my IP anymore (reverse tunnel is way better😬)

interesting. Do you have any tutorials you can point me towards?

Yes, like https://www.youtube.com/watch?v=nmE28_BA83w or https://www.youtube.com/watch?v=B4pnGyvj2sM or https://www.youtube.com/watch?v=Cs8yOmTJNYQ - all very good channels, Techno Tim (that last one) probably explains things more in depth