note1.txt

16-MAY-2019


Hypervisor-based virtual machines-->compute,memory capacity is fixed 
cannot run more workloads on same machines as compared to docker 

1.containers are loosely held isolated environments, 
light weight because they dont need the extra load of hypervisor
they are portable--independent of machine
can run more no of workload on same hardware bcoz of light weight 


2.containers runs directly on the host machine's kernel instead of running on
HOST machine hardware as in VMs

3.Docker containers can run on host machine even if the host machine is a VM

4.Docker engine:client-server model 

docker-client("docker" CLI)<--->REST API<--->server[daemon is  a long running process]("dockerd" cmd)


5. Dockerfile is used to define docker image 




5. DOCKER ARCHITECTURE:

docker daemon 
docker client
docker registeries
docker objects: images, container, services


docker daemon(dockerd): Listens API and manages docker o 


docker-machine ip


docker ps -a

docker run -p 4000:80 -d hello-node:1.0

mapping pod 4000 of local host with port 80 of container 

-d: run in background


"registery collection of repository, 
repository is collection of built images"

dockerhub.io is a registory
username/repo:tag



SERVICES:
*In distributed application, different pieces of app are called as services 
*Services are nothing but "containers in production"
*For creating the services in docker we create "docker-compose.yaml"




before deploying the stack you have to init a swarm

docker swarm init 
docker stack deploy -c docker-compose.yml getstartedlab<stack name>
docker services ls
docker stack services <service-name>