dns rr test

note use nslookup search. with latest alpine image or use older image like alpine:3.10

requirements

• know host to use -it to get shell
• understand basics of different distros (ubuntu vs. centos)
• know how to run a container
• understand basics of dns records

assignment

• since docker engine 1.11 we can have multiple containers on a created network respond to the same dns address
• create a new virtual network (default bridge driver)
• create two containers from elasticsearch:2 image
• research and use --network-alias search when creating them to give an additional dns name to respond to
• run alpine nslookup search with --net to see the two containers list for the same dns name
• run centos curl -s search:9200 with --net multiple times until you see both "name" fields change

answer

--network-alias list             Add network-scoped alias for the container

docker network create search_net
docker network ls
repeat 2 { docker container run -d --net search_net --network-alias search elasticsearch:2 }
docker container run --net search_net -it alpine watch nslookup search.
docker container run --net search_net -it centos curl -s search:9200