Docker, so what is it

⬅️ FEM Docker

• Docker is a command line tool that makes creating, updating packaging, distributing, and running containers significantly easier
• it creates a new environment that’s isolated by namespace and limited by cgroups and chroot’ing you into it

🤔 What is Docker Hub? Docker Hub is a public registry of pre-made containers (it’s like npm for containers) docker pull mongo:3 - will pull the mongo image

🤔 What are images?

• a blueprint that contains the instructions to build a container. It’s an immutable snapshot of the file system and configuration of an application. Images can be easily shared between developers.

docker images # list all images

You can use images to build other images and build on the work of others

# docker command for running skinny linux (alpine)
# starts you in an Alpine ash shell inside of a container 
# as the root user of that container
 
# run means we'll be executing docker (as opposed to building it)
 
# By default containers run and then exit as soon as they're done
# that's why we add the -it flag
 
docker run -it alpine:3.10

🤔 And what are containers?

• A container is a executable package that contains everything needed to run an application. It will always run the same, regardless of infrastructure, in a sandboxed environment. It is a running instance of an image.

docker ps -a # list all containers

So, first you build an image, then you run a container.

🤔 How do you print out currently running containers?

docker ps

🤔 And how do you kill it?

docker kill <id or name>
 
# and to kill all running containers
docker kill $(docker ps -q)

You can name your container:

docker run -dit --name my-ubuntu ubuntu:bionic
docker kill my-ubuntu

🤔 How to free up unused docker space?

 docker container prune

🤔 How do you automatically cleanup the container?

docker run --rm -dit --name my-ubuntu ubuntu:bionic
docker kill my-ubuntu

🤔 How to run a container that comes with node?

# Stretch refers to the version of Debian 
# (which is what the Node.js uses by default.)
 
docker run -it node:12-stretch

🤔 Run it and get dropped in bash?

 
# anything we put after get's evaluated instead of 
# the default command identified by the container
# in node's case that would be node
 
docker run -it node:12-stretch bash

🤔 What is the difference between docker run and docker exec?

• docker run will start a new container
• docker exec runs the command in an already-running container