Use ip route to determine IP

docker_dev.sh

@@ -3,7 +3,7 @@ docker build -f alpine.docker -t diginc/pi-hole:alpine .
 docker tag diginc/pi-hole:alpine diginc/pi-hole:latest
 docker build -f debian.docker -t diginc/pi-hole:debian .
 
-IP=$(ip addr show eth0 | grep "inet\b" | awk '{print $2}' | cut -d/ -f1)
+IP=$(ip route get 8.8.8.8 | awk '{ print $NF; exit }')
 
 # Alternative ports to not conflict with my real instance
 # shellcheck disable=SC2068
@@ -15,4 +15,3 @@ docker run -it --rm --cap-add=NET_ADMIN \
   -e VIRTUAL_HOST='pihole.diginc.lan:5080' \
   $@ \
   diginc/pi-hole:"${image:-alpine}"
-

docker_run.sh

@@ -1,7 +1,6 @@
 #!/bin/bash
 IMAGE=${1:-'diginc/pi-hole:alpine'}
-NIC=${2:-'eth0'}
-IP=$(ip addr show "$NIC" | grep "inet\b" | awk '{print $2}' | cut -d/ -f1)
+IP=$(ip route get 8.8.8.8 | awk '{ print $NF; exit }')
 
 # Default ports + daemonized docker container
 docker run -p 53:53/tcp -p 53:53/udp -p 80:80 \