Access docker application by hostname

To access a docker application by a particular hostname, the file: /var/lib/docker/containers/CONTAINER_ID/config.json requires the change of the Hostname and Domainname "Config":{"Hostname":"www","Domainname":"example.local", ...}. This way, the container will have all the necesarry information.

An elegant way, instead of directly editing the configuration file, is to use docker-compose (aka fig) to run the application:

...
    web:
        image: example/application
        hostname: www
        domainname: example.local
        ports:
            - "80:80"
        volumes:
            - /var/www
...

The next little script will search all active containers, get that necessary info for the /etc/hosts file and adjust it with the required names:

#!/bin/bash

FILE=/etc/hosts
DEFAULT_DOMAIN='example.local'
for CID in $(docker ps  --filter="name=$name" -q); do
  IP=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' ${CID})
  HOSTNAME=$(docker inspect --format '{{ .Config.Hostname }}' ${CID})
  DOMAINNAME=$(docker inspect --format '{{ .Config.Domainname }}' ${CID})
  if [ -n "$HOSTNAME" ] && [ -n "$DOMAINNAME" ]; then
    HOST="$HOSTNAME.$DOMAINNAME"
  else
    HOST="$CID.$DEFAULT_DOMAIN"
  fi

  sed -i "/\b$IP\b/d" $FILE

  if grep -q $HOST "$FILE"; then
    sed -i "/$HOST/ s/.*/$IP\t$HOST/g"
  else
    echo -e "\n$IP	$HOST" >> $FILE
  fi

done

After running the script, the application should be available now at: http://www.example.local.

UPDATED:

Another way is to add a bridge network on the host, giving a static IP address such as 192.168.33.100.

After that the docker port forwarding which accept IP address as well should be use. In docker compose yaml the syntax is:

...
    ports:
        - "192.168.33.100:80:80"
...

The file /etc/hosts needs to be updated with the IP pointing to www.example.local. This way can be added as many bridges having different static IPs with only only modification of the /etc/hosts file per docker/docker-compose project.