I have two Rails docker containers:
The first is the the front-end application (container1) and the other is the backend API (container2).
The frontend can be access at http://0.0.0.0:3000. The front-end connects to the backend API via http://0.0.0.0:5000.
I have used this to start the frontend linking it to the backend
docker run --name=frontend --publish=3000:3000 --link=postgis:postgres --link=backend:backend --volume=/var/app:/app --tty=false --interactive=false --detach=true frontend
Backend is running as usual
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
cd4521524caf backend "/bin/bash -l -c /setu" About an hour ago Up About an hour 0.0.0.0:5000->5000/tcp backend
The linked backend I observed has added an entry in the /etc/hosts
172.17.0.712 cd4521524caf
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.2 postgres 12b29087618e postgis
How can I get/expose the name and alias of my backend docker container to register properly in /etc/hosts and also how can I expose an environment variable that will have the value of 172.17.0.12:5000.
I noticed other docker containers (like postgis) that I have linked add environment variables but mine (backend) doesn't.
I would like my environment variable to be like
BACKEND_API="http://172.17.0.12:5000"
And the /etc/hosts entry to be:
172.17.0.712 backend cd4521524caf backend
If your software supports name resolution via /etc/hosts (which is very, very likely unless you're doing name resolution by hand in the frontend), you could just use -e BACKEND_API="http://backend:5000" and it will automatically pull the correct IP from /etc/hosts directly.