Docker

Installation

curl -fsSL https://get.docker.com -o get-docker.sh | sh
sudo usermod -aG docker <username>

Checking the installation

docker version -> check for status of the server and client

docker info -> config values

docker -> Gives list of all commands available

• Docker cli structure
  • docker <command> -> old way
  • docker <command> <sub-command> -> format of the management command

Basics - Creating and using containers

Container vs VM

Image vs Containers

Image -> Binaries, Libraries, Source code the make up the application

Container -> Running instance of that image, Can have many container running off of same image

Basics of docker containers

docker container run --publish 80:80 nginx

docker container run --publish 80:80 --detach nginx : Runs the container in the background

docker container run --publish 80:80 --detach --name myserver nginx: Specify custom name

docker container ls: Lists all the running containers

docker container ls -a: Lists all the containers

Run vs Start

docker container run: Starts a new container

docker container start: Starts an existing stopped container

Checking logs

docker container logs <name>

Docker container commands list

Working of docker container run command

Other docker commands

docker search <name>: Search on docker hub for image docker images: List all local images

Inside the containers

docker container top <name>: Information about the processes running inside the container

docker container inspect <name>: Metadata about the container (JSON format)

docker container stats <name>: Performance stats about all containers

Getting a shell inside a container

docker container run -it

• i: interactive
• t: allocate a pseudo tty

docker container start -ai <name>

• a: Attach STDOUT/STDERR and forward signals

• i: Attach container's STDIN

• docker container exec -it <name>: Run commands inside an already running container

• We can only run the command which already exist inside the image

Networking in docker

docker container run -p host:container: Publish a container's port(s) to the host

docker container port <name>: Get port details for the container

• How docker moves packets in and out

CLI network management

• docker network ls: Lists all networks
  • bridge: Virual network
  • host: No virtual network, Directly connected to host
  • null : No network only localhost
• docker network inspect <name>: Info about the network
• Attaching a container to a network at start
• docker network connect <network> <container>: Attach a container to a network, Dynamically creates a NIC in the container connected to a virtual network
• docker network disconnect <network> <container>

DNS

• Static IPs and Using IPs to talk to containers is an antipattern, Avoid it
• Docker daemon has a built-in DNS server that containers use by default
• Docker defaults the hostnames to the container's name
• The default bridge network does not have the built-in DNS server by default, We can use docker container run --link <list> to link the containers to each other in the default bridge network