technical:docker-lab-basic [RADIUSdesk]

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====== Description ======
  * We start out with a very basic Docker lab to build out confidence.
      * Two plain Nginx containers.
      * Run them on a bridge called **test-radiusdesk**
      * Reach them on ports 8000 and 8001 respectively from the host Linux system laptop running Docker.

====== 1. Create the bridge ======
  * Create the bridge
<code bash>
docker network create test-radiusdesk
#This was the result
f67e11184a174cf7fb82ba85734dd6d895f0690738cb07246fd7ee13b0024761
</code>
  * Confirm it was created:
<code bash>
docker network ls
#This was the result
NETWORK ID     NAME                DRIVER    SCOPE
395e31953e3c   bridge              bridge    local
0d8b3aa905bf   host                host      local
17e0830302a8   none                null      local
f67e11184a17   test-radiusdesk     bridge    local
</code>
  * If you issue the //ip a// command it will be listed there (Look for the NETWORK ID)
<code bash>
17: br-f67e11184a17: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether fe:67:4b:58:62:66 brd ff:ff:ff:ff:ff:ff
    inet 172.20.0.1/16 brd 172.20.255.255 scope global br-f67e11184a17
       valid_lft forever preferred_lft forever
</code>

====== 2.Run two nginx containers on that bridge ======
  * Issue the following commands (We will use //docker up// first)
<code bash>
# Container 1 -> host port 8000
docker run -d --name nginx-8000 --network test-radiusdesk -p 8000:80 nginx

# Container 2 -> host port 8001
docker run -d --name nginx-8001 --network test-radiusdesk -p 8001:80 nginx
</code>
  * What that does:
    * --network test-radiusdesk plugs both into your custom bridge
    * -p 8000:80 means laptop port 8000 forwards to container port 80

====== 3. Test from your laptop ======
  * Use curl or your browser
<code bash>
curl http://localhost:8000
curl http://localhost:8001
</code>
  * Both should show "Welcome to nginx!"


====== 4. Prove they can talk to each other by name (the bridge magic) ======
  * Issue this command:
<code bash>
docker exec -it nginx-8000 ping nginx-8001
</code>
  * It will resolve! On the default bridge this would NOT work.
  * Another test:
<code bash>
docker exec -it nginx-8000 curl http://nginx-8001
</code>
  * Container 8000 reaching container 8001 internally on port 80, without going through your host ports.

====== Useful cleanup / debug ======
  * Some handy commands:
<code bash>
docker ps                           # see running
docker network inspect test-radiusdesk  # see which containers + their IPs
docker logs nginx-8000
docker stop nginx-8000 nginx-8001 && docker rm nginx-8000 nginx-8001
docker network rm test-radiusdesk
</code>

====== Same thing with docker-compose (cleaner) ======
  * Create docker-compose.yml:
<code yaml>
services:
  nginx-8000:
    image: nginx
    ports:
      - "8000:80"
    networks:
      - test-radiusdesk

  nginx-8001:
    image: nginx
    ports:
      - "8001:80"
    networks:
      - test-radiusdesk

networks:
  test-radiusdesk:
    driver: bridge
</code>
  * We can then bring it up with:
<code bash>
docker compose up -d
docker compose down
</code>