Essential Docker Commands

PULL - To pull a docker image use the pull flag i.e docker pull {image name}:latest
- Note: Always use the alpine version of the docker image cause its light weight and faster to pull. So always check for the alpine version of images and pull them.
SHOW DOCKER IMAGES - To show the list of all docker images docker images ls
SHOW RUNNING CONTAINER - To show all running docker containers use docker ps || docker container ls.
- docker ps shows a list of the running containers.
  - To nicely format the output of output of docker ps use the -format="ID\t{{.ID}}\nNAME\t{{.Names}}\nImage\t{{.Image}}\nPORTS\t{{.Ports}}\nCOMMAND\t{{.Command}}\nCREATED\t{{.CreatedAt}}\nSTATUS\t{{.Status}}\n" flag.
  - To shorten this store the value in a variable using this command export FORMAT="ID\t{{.ID}}\nNAME\t{{.Names}}\nImage\t{{.Image}}\nPORTS\t{{.Ports}}\nCOMMAND\t{{.Command}}\nCREATED\t{{.CreatedAt}}\nSTATUS\t{{.Status}}\n". Now you can use docker ps --format=$FORMAT to show the nicely formatted output.

RUN CONTAINER - To run a docker container use docker run {name of the docker image}:{the version of the docker image} || docker run -d {name of the docker image}:{version of the docker image}
- Most time we run the latest version of the docker image.
- -d flag means you are specify that this container should be detached and run in the background.
PORT - To specify a port to attach a container to use the -p and then specifying the port flag when running the container docker run -d -p 8000:80 {name of the docker image}:{version of the docker image}
- Note: You can specify more than one port to attach to a container you want to run docker run -d -p 8000:80 -p 3000:80 {name of the docker image}:{version of the docker image}.
Network - To connect a container to a network use the --net flag and then specify the network name. So if you want to connect the container to a network called bridge use this flag --net=bridge.
- Note: You can connect a container to more than one network by specifying the network name multiple times.
Enviroment Variable - To specify an environment variable use the -e flag and then specifying the environment variable flag when running the container docker run -d -e {name of the environment variable}={value of the environment variable} {name of the docker image}:{version of the docker image}
- Note: You can specify more than one environment variable to attach to a container you want to run docker run -d -e {name of the environment variable}={value of the environment variable} -e {name of the environment variable}={value of the environment variable} {name of the docker image}:{version of the docker image}.

STOP CONTAINER - To stop a docker container use docker stop {the container id} || docker stop {container name}
DELETE CONTAINER - To delete a container use docker rm {the container id}
INSPECT - To inspect a container use docker inspect {the container id}
LOGS - To show logs of a container use docker logs {the container id}. Logs are essential whe you want to debug.
- To see all useful commands you can use alongside logs use the --help flag.
- To continuously show logs of a container use -f flag, i.e docker logs -f {the container id}.
DELETE IMAGE - To delete a docker image docker image rm {the image id} || docker rmi {repository}:{tag}.
DELETE ALL CONTAINER REGISTRY - To remove all containers from registry use docker rm $(docker ps -aq)
- Note: To forcefully remove a running container use -f flag i.e docker rm -f {docker ps -aq}.

NAME CONTAINER - To name a container use the --name flag. i.e docker run --name {what you want to name the container} -d -p 3000:80 {name of the docker image}:{version of the docker image}
SHARE VOLUMES - To share a volume || folder || project with a docker container running on nginx for instance you need to use the -v flag or command which stringifies volume. first cd into the project directory and run docker run --name {name you want to call the container} -v $(pwd):/usr/share/nginx/html:ro -d -p 8080:80 nginx:latest
- NB: the $(pwd) command gives you the current working directory. In this instance its the folder you've cd into.
- To share volumes between two docker containers, use the --volume-from flag for instance sudo docker run --name divine-copy --volumes-from divine -d -p 3000:80 nginx:latest

Creating a DOCKER file

Create a cutom docker image A image should contain all the things your application needs to run

First create a docker file touch Dockerfile inside the project you want to dockerize then. Inside this file specify
- FROM => The FROM instruction initializes a new build stage and sets the Base Image for subsequent instructions. As such, a valid Dockerfile must start with a FROM instruction. The image can be any valid image – it is especially easy to start by pulling an image from the Public Repositories. for instance use the nodejs official docker image node:latest
- ADD => The ADD instruction copies new files, directories or remote file URLs from <src> and adds them to the filesystem of the image at the path. For instance to add all files || folders in the root directory use double dots . .
- RUN => The RUN instruction will execute any commands in a new layer on top of the current image and commit the results. The resulting committed image will be used for the next step in the Dockerfile. For instance you can instal npm all packages inside the container using the RUN instruction i.e npm install
- CMD => There can only be one CMD instruction in a Dockerfile. If you list more than one CMD then only the last CMD will take effect. The main purpose of a CMD is to provide defaults for an executing container. These defaults can include an executable, or they can omit the executable, in which case you must specify an ENTRYPOINT instruction as well. For instance you can run a nodejs application using the RUN instruction i.e node app.js.
To create a container in docker use the docker build command. For instance docker build -t divine-website:latest . this will build a docker image from our dockerfile thats inside the our project directory. To see all available docker build command use docker build --help. NB: always use -t or --tag flag to add a tag to a container

Tags, Versioning ang Tagging

Tags =>

To create a tag use the tag flag like so docker tag {from latest version of the docker image} { to version 1.0 of the docker image} eg sudo docker tag divine-website:latest divine-website:1.1

Versioning =>

To create a version for a container you need the specify the version when running the container like docker run --name {name you want to call the container} -d -p 5000:80 {the docker image}:{the version}. For instance I want to create a new container from an image I have already created, I will run docker run --name divine-website-v1 -d -p 5000:80 divine-website:1.1. NB: 1.1 in this instance is the a tag for this docker image which specifies the version

Docker Registry

There are two types of registries which are, Public and Private Registry. You can push this registries to docker registry providers like Docker HUB, Quay.io, Amazon ECR.

To push a new docker image to a docker registry use the docker push instruction. eg docker push codewithdiv/nodejs-api:tagname. NB: Before you push to a docker registry first tag the image you want to push docker tag {repository name} {with the name of registry you want to push to, eg - codewithdiv/nodejs-api:tagname}

Docker Networks

What is a docker network? A docker network is a virtual network that you can use to connect containers to each other.
To get the list of all networks use the docker network ls command.
To create a docker network use the docker network create instruction. eg docker network create {name of the network}
To connect a container to a network use the docker network connect instruction. eg docker network connect {name of the network} {name of the container}
- Note: You can connect multiple containers to a network by using the docker network connect instruction multiple times.
To disconnect a container from a network use the docker network disconnect instruction. eg docker network disconnect {name of the network} {name of the container}

zerothebahdman / docker