Learn Docker in 7 Easy Steps - Full Beginner's Tutorial
Summary
TLDRThis video script offers an in-depth tutorial on Docker for developers, focusing on containerizing a Node.js application. It covers Docker's basics, including Dockerfiles, images, and containers, and addresses advanced topics like port forwarding and volumes. The tutorial guides viewers through installation, writing Dockerfiles, building and running images, and managing multi-container setups with Docker Compose, aiming to demystify Docker and empower developers to package and deploy applications consistently across any environment.
Takeaways
- 📦 Docker is a tool for packaging software so it can run on any hardware, helping to standardize development environments.
- 🛠️ The core components of Docker are Dockerfiles, images, and containers, which work together to build, distribute, and run applications consistently.
- 💡 Docker solves the 'it works on my machine' problem by allowing developers to define and reproduce environments with Dockerfiles.
- 📝 A Dockerfile is a script with instructions to build a Docker image, which serves as a template for creating containers.
- 🚀 The process of Dockerizing an application involves creating a Dockerfile, installing dependencies, and defining how the application runs within a container.
- 🖥️ Docker Desktop is recommended for Mac or Windows users, providing both command-line access and a GUI for managing containers.
- 🔍 Docker extensions for IDEs like VS Code enhance development by providing language support for Dockerfiles and integration with registries.
- 🔑 The 'FROM' instruction in a Dockerfile starts with a base image, which can be an official image like 'node:12' to simplify setup.
- 🔄 Efficient layer caching in Dockerfiles is achieved by installing dependencies before copying the source code, minimizing rebuild times.
- 🔒 Dockerignore files help to exclude unnecessary files like 'node_modules' from being copied into the Docker image, keeping the image lean.
- 🔌 Port forwarding is essential for accessing applications running inside containers from the host machine, using the '-p' flag in 'docker run'.
- 🔄 Volumes in Docker allow data persistence and sharing across containers, useful for databases and other stateful services.
- 🔧 Docker Compose simplifies the management of multi-container applications by defining and running services, volumes, and networking in a YAML file.
- 🔄 Debugging Dockerized applications can be done through logs, direct CLI access within containers, or using Docker Desktop's GUI.
Q & A
What is one of the leading causes of imposter syndrome among developers mentioned in the script?
-Not knowing Docker and feeling left out during discussions about advanced topics like Kubernetes, swarms, and sharding at parties.
What is the main goal of the video?
-To teach developers everything they need to know about Docker, including installation, Dockerfile instructions, and advanced concepts like port forwarding, volumes, and Docker Compose.
What are the three essential concepts in Docker that one must understand?
-The three essential concepts are Dockerfiles, images, and containers. A Dockerfile is a blueprint for building a Docker image, an image is a template for running containers, and a container is a running process of that image.
Why is Docker useful for developers?
-Docker is useful for developers because it packages software so it can run on any hardware, ensuring that applications run consistently across different environments and avoiding issues like 'it works on my machine'.
What is the purpose of a Dockerfile?
-A Dockerfile is used as a blueprint to build a Docker image, which is then used to create containers. It contains a set of instructions that define the environment in which the application will run.
How does Docker solve the problem of different environments causing application failures?
-Docker solves this problem by allowing developers to define the environment in a Dockerfile, creating an immutable snapshot known as an image. This image can be used to spawn the same process in multiple places, ensuring consistency.
What command should one memorize after installing Docker?
-The 'docker' command should be memorized as it lists all the running containers on the system.
Why is it important to install the Docker extension for VS Code or another IDE?
-The Docker extension provides language support when writing Dockerfiles, and it can also link up to remote registries, offering additional functionality and convenience.
What is the significance of the 'FROM' instruction in a Dockerfile?
-The 'FROM' instruction specifies the base image to start from when building the Docker image. It's typically a specific version of an operating system or a language runtime environment.
Why should dependencies be installed before the app source code in a Dockerfile?
-Installing dependencies first allows Docker to cache them, which means that they don't need to be reinstalled every time the app source code changes, making the build process more efficient.
What is the purpose of the 'docker build' command?
-The 'docker build' command is used to build a Docker image from a Dockerfile. It processes each instruction in the Dockerfile and creates an image that can be used to run containers.
How can one access a running Docker container's logs and interact with its command line?
-One can access logs and interact with a Docker container's command line using Docker Desktop's GUI, which provides a dashboard for viewing logs and a CLI button for executing commands, or by using the 'docker exec' command from the command line.
What is Docker Compose and how does it help with running multiple containers?
-Docker Compose is a tool for defining and running multi-container Docker applications. It allows you to configure your application's services, networks, and volumes in a 'docker-compose.yaml' file and start all the containers together with a single command.
Why should each container in a Dockerized application ideally run only one process?
-Running only one process per container helps keep the containers simple and maintainable. It also aligns with the microservices architecture, making it easier to manage and scale individual components of the application.
Outlines
📦 Understanding Docker Basics for Developers
This paragraph introduces the concept of imposter syndrome among developers due to unfamiliarity with Docker, a tool for containerization. It outlines the importance of Docker in modern development practices and promises a step-by-step guide to mastering Docker by containerizing a Node.js application. The paragraph explains the basic components of Docker, including Dockerfiles, images, and containers, and emphasizes Docker's role in creating reproducible software environments. It also touches on advanced Docker concepts such as port forwarding, volumes, and Docker Compose for managing multiple containers.
🛠 Docker Installation and Dockerfile Essentials
The second paragraph delves into the installation process of Docker, recommending Docker Desktop for Mac and Windows users. It details the first Docker command to memorize and the importance of the Docker extension for IDEs like VS Code. The main focus then shifts to the Dockerfile, which is the core of building a Docker image. The paragraph walks through creating a Dockerfile, starting with choosing a base image, adding app source code, and installing dependencies. It also discusses best practices for Dockerfile instructions, such as caching layers for efficiency and using the 'docker ignore' file to avoid copying unnecessary files into the image. The paragraph concludes with how to set environment variables, expose ports, and the significance of the 'command' instruction in the Dockerfile for running the application.
🔧 Building and Running Docker Images
This paragraph explains the process of building a Docker image using the 'docker build' command, including how to tag images for easy identification and retrieval. It describes the build process starting from pulling the base image to executing each step in the Dockerfile. The paragraph also covers how to run a Docker container locally using the 'docker run' command and the importance of port mapping for external access to the container's services. Additionally, it discusses the persistence of container data using volumes and how to manage and debug containers using Docker Desktop or command-line tools like 'docker exec'. The paragraph wraps up with a brief introduction to Docker Compose for orchestrating multiple containers, which is particularly useful for complex applications requiring services like databases.
🔄 Orchestrating Containers with Docker Compose
The final paragraph introduces Docker Compose as a tool for defining and running multi-container Docker applications. It provides an overview of creating a 'docker-compose.yaml' file to configure services, such as a Node.js app and a MySQL database, along with volume definitions for data persistence. The paragraph explains how to use YAML syntax to simplify the configuration of multiple containers and services. It concludes with the execution of 'docker compose up' to start all services together and 'docker compose down' to shut them down, emphasizing the ease of managing containerized applications with Docker Compose.
Mindmap
Keywords
💡Imposter Syndrome
💡Docker
💡Container
💡Dockerfile
💡Docker Image
💡Port Forwarding
💡Volumes
💡Docker Compose
💡Node.js
💡Environment Variables
💡Microservices
Highlights
Imposter syndrome among developers can be caused by a lack of Docker knowledge.
Docker helps package software to run on any hardware, solving 'it works on my machine' problems.
Understanding Docker involves knowing about Dockerfiles, images, and containers.
A Dockerfile is a blueprint for building a Docker image.
Docker images are templates for running Docker containers.
Containers are running processes that can be created from an image.
Docker can reproduce environments defined by developers to ensure consistency.
Images can be uploaded to public and private registries for easy access.
Docker Desktop application is recommended for Mac and Windows users.
Docker extension for VS Code provides language support and remote registry linking.
The Dockerfile contains instructions to build a Docker image and run an application.
Base images like 'node:12' are used to provide a starting environment for Dockerfiles.
Dependencies should be installed first in a Dockerfile to leverage Docker's layer caching.
Dockerignore file helps to exclude unnecessary files like 'node_modules' from being copied.
Environment variables and port exposure are set in the Dockerfile for container configuration.
The 'exec form' in Dockerfile is preferred for running the application process.
Docker images are built using the 'docker build' command with a tag for easy access.
Port forwarding is implemented using the '-p' flag to make containers accessible locally.
Volumes are used in Docker to share data across multiple containers and persist data.
Docker Compose is a tool for running multiple Docker containers simultaneously.
Docker Compose uses a 'docker-compose.yaml' file to define and run services and volumes.
Docker Compose allows for easy scaling of containers with tools like Kubernetes and Swarm.
Debugging Docker containers can be done through logs, CLI access, and Docker Desktop GUI.
Docker encourages the development of simple, maintainable microservices.
Transcripts
one of the leading causes of imposter
syndrome among developers is not knowing
docker it makes it hard to go to parties
where everybody's talking about
kubernetes
swarms shuffle sharding while you hide
in the corner googling what is a
container we've all been there at one
point or another
in today's video you'll learn everything
you need to know about docker to survive
as a developer in 2020
we'll take a hands-on approach by
containerizing a node.js application
i'll assume you've never touched a
docker container before so we'll go
through installation and tooling
as well as the most important
instructions in a dockerfile in addition
we'll look at very important advanced
concepts like port forwarding
volumes and how to manage multiple
containers with docker compose
we'll do everything step by step so feel
free to skip ahead with the chapters in
the video description
what is docker from a practical
standpoint it's just a way to package
software so it can run on any hardware
now in order to understand how that
process works there are three things
that you absolutely must know
docker files images and containers a
docker file is a blueprint for building
a docker image
a docker image is a template for running
docker containers
a container is just a running process in
our case we have a node application we
need to have a server that's running the
same version of node and that has also
installed these dependencies
it works on my machine but if someone
else with a different machine tries to
run it with a different version of node
it might break
the whole point of docker is to solve
problems like this by reproducing
environments the developer who creates
the software can define the environment
with a docker file
then any developer at that point can use
the docker file to rebuild the
environment which is saved as an
immutable snapshot known as an image
images can be uploaded to the cloud in
both public and private registries
then any developer or server that wants
to run that software
can pull the image down to create a
container which is just a running
process of that image in other words one
image file can be used to spawn the same
process multiple times in multiple
places
and it's at that point where tools like
kubernetes and swarm come into play
to scale containers to an infinite
workload the best way to really learn
docker
is to use it and to use it we need to
install it if you're on mac or windows i
would highly recommend installing the
docker desktop application it installs
everything you need for the command line
and also gives you a gui where you can
inspect your running containers
once installed you should have access to
docker from the command line and here's
the first command you should memorize
docker which gives you a list of all the
running containers on your system
you'll notice how every container has a
unique id and is also linked to an image
and keep in mind you can find the same
information from the gui as well now the
other thing you'll want to install is
the docker extension for vs code or for
your ide
this will give you language support when
you write your docker files and can also
link up to remote registries and a bunch
of other stuff
now that we have docker installed we can
move on to what is probably the most
important section of this video and
that's the docker file
which contains code to build your docker
image and ultimately run your app as a
container
now to follow along at this point you
can grab my source code from github or
fireship io or better yet
use your own application as a starting
point in this case i just have a single
index.js file
that exposes an api endpoint that sends
back a response
docker is easy then we expose our app
using the port environment variable
and that'll come into play later the
question we're faced with now is how do
we dockerize this app
we'll start by creating a docker file in
the root of the project
the first instruction in our docker file
is from and if you hover over it it will
give you some documentation about what
it does
you could start from scratch with
nothing but the docker runtime however
most docker
files will start with a specific base
image for example
when i type ubuntu you'll notice it's
underlined and when i control click it
it will take me to all the base images
for this flavor of linux and then you'll
notice it supports a variety of
different tags which are just different
variations on this base image
ubuntu doesn't have nodejs installed by
default we could still use this image
and install node.js manually
however there is a better option and
that's to use the officially supported
node.js image
we'll go ahead and use the node version
12 base image which will give us
everything we need to start working with
node in this environment
the next thing we'll want to do is add
our app source code to the image
the working directory instruction is
kind of like when you cd into a
directory
now any subsequent instructions in our
docker file will start from this app
directory
now at this point there is something
very important that you need to
understand
and that's that every instruction in
this docker file is considered its own
step or layer
in order to keep things efficient docker
will attempt to cache layers
if nothing is actually changed now
normally when you're working on a node
project
you get your source code and then you
install your dependencies but in docker
we actually want to install our
dependencies first so they can be cached
in other words we don't want to have to
reinstall all of our node modules every
time we change our app source code we
use the copy instruction which takes two
arguments
the first argument is our local package
json location
and then the second argument is the
place we want to copy it in the
container which is the current working
directory
and now that we have a package json we
can run the npm install command
this is just like opening a terminal
session and running a command
and when it's finished the results will
be committed to the docker image as a
layer
now that we have our modules in the
image we can then copy over our source
code
which we'll do by copying over all of
our local files to the current working
directory
but this actually creates a problem for
us because you'll notice that we have a
node modules folder here in our local
file system
that would also be copied over to the
image and override the node modules that
we install there
what we need is some kind of way for a
docker to ignore our local node modules
we can do that by creating a docker
ignore file
and adding node modules to it it works
just like a git ignore file which you've
probably seen before
okay so at this point we have our source
code in the docker image
but in order to run our code we're using
an environment variable we can set that
environment variable in the container
using the env
instruction now when we actually have a
running container we also want it to be
listening on port 8080 so we can access
the nodejs express app publicly
and we'll look at port some more detail
in just a minute when we run the
container
and that brings us to our final
instruction command there can only be
one of these per docker file and it
tells the container how to run the
actual application
which it does by starting a process to
serve the express app you'll also notice
that unlike run
we've made this command an array of
strings this is known as exec form
and it's the preferred way to do things
unlike a regular command it doesn't
start up a shell session
and that's basically all there is to it
we now have a full set of instructions
for building a docker image
and that brings us to the next question
how do we build a docker image
you build a docker image by running the
docker build command there's a lot of
different options you can pass with the
command but the one you want to know for
right now
is tag or t this will give your image a
name tag that's easy to remember so you
can access it later
when defining the tag name i'd first
recommend setting up a username on
docker hub
and then do that username followed by
whatever you want to call this image
so in my case it would be fireship slash
demo app and you could also add a
version number separated by a colon
from there you simply add the path to
your docker file which in our case is
just a period for the current working
directory
when we run it you'll notice it starts
with step one which is to pull the node
12 image remotely
then it goes through each step in our
docker file and finally it says
successfully built the
image id and now that we have this image
we can use it as a base image to create
other images or we can use it to run
containers
in real life to use this image you'll
most likely push it to a container
registry somewhere
that might be docker hub or your
favorite cloud provider and the command
you would use to do that is
docker push then a developer or server
somewhere else in the world could use
docker pull to pull that image back down
but we just want to run it here locally
in our system so let's do that with the
docker run command
we can supply it with the image id or
the tag name and all that does
is create a running process called a
container and we can see in the terminal
it should say app listening on localhost
8080. but if we open the browser and go
to that address we don't see anything
so why can't i access my container
locally remember we exposed port 8080 in
our docker file
but by default it's not accessible to
the outside world let's refactor our
command to use the p
flag to implement port forwarding from
the docker container to our local
machine
on the left side we'll map a port on our
local machine 5000 in this case
to a port on the docker container 8080
on the right side
and now if we open the browser and go to
localhost 5000 we'll see the app running
there
now one thing to keep in mind at this
point is that the docker container will
still be running even after you close
the terminal window
let's go ahead and open up the dashboard
and stop the container you should
actually have two running containers
here if you've been following along
when you stop the container any state or
data that you created inside of it will
be lost
but there can be situations where you
want to share data across multiple
containers
and the preferred way to do that is with
volumes a volume is just a dedicated
folder on the host machine
and inside this folder a container can
create files that can be remounted into
future containers or multiple containers
at the same time
to create a volume we use the docker
volume create command
now that we have this volume we can
mount it somewhere in our container when
we run it
multiple containers can mount this
volume simultaneously and access the
same set of files
and the files stick around after all the
containers are shut down
now that you know how to run a container
let's talk a little bit about debugging
when things don't go as planned you
might be wondering how do i inspect the
logs and how do i get into my container
and start interacting with the command
line
well this is where docker desktop really
comes in handy if you click on the
running container you can see all the
logs right there
and you can even search through them you
can also execute commands in your
container by clicking on the cli button
and keep in mind you can also do this
from your own command line using the
docker exec command
in any case it puts us in the root of
the file system of that container so we
can then ls to see files
or do whatever we want in our linux
environment that's useful to know but
one of the best things you can do to
keep your containers healthy
is to write simple maintainable micro
services each container should only run
one process
and if your app needs multiple processes
then you should use multiple containers
and docker has a tool designed just for
that called docker compose
it's just a tool for running multiple
docker containers at the same time
we already have a docker file for our
node app but let's imagine that our node
app also needs to access a mysql
database
and we also likely want a volume to
persist the database across multiple
containers
we can manage all that with docker
compose by creating a
docker-compose.yaml file in the root of
our project
inside that file we have a services
object where each key
in that object represents a different
container that we want to run
we'll use web to define our node.js app
that we've already built
and then we'll use build to point it to
the current working directory which is
where it can find the docker file
and then we'll also define the port
forwarding configuration here as well
then we have a separate container called
db which is our mysql database process
after services we'll also define a
volume to store the database data across
multiple containers
and then we can mount that volume in our
db container and hopefully you're
starting to see how much
easier it is to define this stuff as
yaml as opposed to writing it out as
individual commands
and now that we have this configuration
set we can run docker compose up from
the command line which will find this
file
and run all the containers together we
can mess around with our app for a
little while
and then run docker compose down to shut
down all the containers together
i'm going to go ahead and wrap things up
there if this video helped you please
like and subscribe and consider becoming
a pro member at fireship io
where we use docker in a variety of
different project-based courses
thanks for watching and i will see you
in the next one
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