Docker - Containerizing an App

Containerizing an App:

CODE - DOCKERFILE - BUILD -IMAGE

To get our code into Container we need something called Dockerfile

Dockerfile - List of instructions on how to build an image with an app inside. 

The above Dockerfile contains 4 layers and some metadata

Now build an image

docker image build -t apiembark . 

Now run a container from that image

docker container run -d --name test_app -p 8080:8080 apiembark

Code ->Dockerfile -> Docker Image Build

Build Context - Location of our code (My Dockerfile is located in the build context)

But when you type docker image build whatever is in there is get sent to the daemon and processes part of the build.

Now for us, the client and daemon are on the same host

but it is totally possible to have clients talking to remote Daemons over the network

In that case, our build context can absolutely be a remote gihub repo

docker image build -t apiembark https://github.com/project_url

Multi-Stage Builds

Size matters when its come to images

smaller the definitely better

Advantages of smaller images:

• Faster builds
• Faster deployments
• less money wasted on storage
• less attack surface for the bad guys to aim at

So running our Apps with minimal OS and minimal supporting packages that is the Gold standard

Working with containers:

docker container ls

To login into the container

docker container run -it [IMAGE_NAME] [WHAT PROCESS TO USE]

docker container run -it alpine sh

docker container exec -it [CONT ID or CONT NAME] [WHAT PROCESS TO USE]

docker container exec -it 60 sh

After login into the container to check what are all the process running

ps -elf

we can directly run some commands on the container 

docker container exec 60 la -l

we can output any files from the container

docker container exec 60 cat newfile 

CTRL P+Q is gracefully way of getting out of the container without terminating its main process