THe files in this directory: 

docker-compose.yml 
  This file brings up two containers. one with nginx (see contained directory nginx-rev for how  
  that container is built. THe nginx container has the facilities to execute the swap
  Which port is the  ngnix listenign on?  WHy is it mapped? 
  Why is the port on the other container not mapped? Can it be accessed from outside
  the container? Is that necessary? Why and why not? 


cleanup.sh (no arguments) 
  good idea to execute this once in a while, to clean up "zombie" docker images that are halted 
 
dorun.sh (no arguments) 
  1) this shell uses the yml file to bring up the docker network
  2) when the nginx comes up, it's pointing at the UC Davis engineering school. 
  3) once the network comes up, it tells the nginx container, using the "init.sh" shell
  script (see the directory below) to redirect the requests to the actual working directory. 
  4) Note that the dorun.sh uses docker-compose command? Where does this command look for more details? 
  5) What does the "-p" option do? Look it up in teh dcoumentation
  6) What does the "docker exec... init.sh" do? why is there a sleep before it? 
  
(FOR 25% EXTRA CREDIT, WRITE the next shell script. Otherwise, you can just
demonstrate the swap  by hand.)

doswap.sh (one argument, the docker image, say DDDD, you want to run) (WRITE THIS FOR EXTRA CREDIT!!) 
  1) if the current "live" container is named web1, then, it kills any existing one named
      web2 brings up the new DDD named  web2. 
  2) it tells the nginx to send the requests henceforth to web2. (using the swap1 shell script) 
  3) it kills the web1
  4) if the otherway around web1<->web2 using Swap2 shell script. 
  5) HINT: Be Careful, to give enough time (using "sleep n" for n seconds) for things to happen in sequence. 
  6) HINT: you may have to kill existing containers just make sure it's workign fine. Look at the "killitif" reoutine