demystifying-docker-previous/slides.md

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# Demystifying Docker

A beginners guide to containerization and beyond

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# Who am I?

Mike Conrad

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# What is a container?

> A method for packaging and securely running an application within an application virtualization environment. Also known as an application container or a server application container. [NIST](https://csrc.nist.gov/glossary/term/container)

<p style="background:white;height:20px;"></p>

> A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another. A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings. [Docker](https://www.docker.com/resources/what-container/)

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# Problems?

- 📝 **It works on my machine?!?!** - Code behaves differently in dev, testing, and production due to differences in environment (OS, dependencies, configurations).
- 🎨 **Dependency conflicts** - Different applications require conflicting versions of the same dependency (e.g., Python 2 vs 3, different Node versions).
- 🧑‍💻 **Slow and error-prone deployments** - Traditional deployments involve manual steps or configuration drift between environments.

::right::
# Solutions

- Containers package the application and its dependencies in a consistent, isolated environment, ensuring it behaves the same everywhere.
- Containers isolate applications and their dependencies from each other and the host system, preventing conflicts.
- Containers provide predictable, repeatable, and scriptable deployments through container images.
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# Problems?

- 📝 **Inefficient resource usage in virtual machines (VMs)** - VMs have high overhead due to running full operating systems, leading to inefficiency.
- 🎨 **Difficult scalability and orchestration** - Scaling applications manually is hard and error-prone.
- 🧑‍💻 **Inconsistent development workflows** - devs all have different setups, leading to inconsistent builds and bugs.

::right::
# Solutions

- Containers share the host OS kernel and are more lightweight, enabling faster startup and denser packing of applications.
- Containers integrate well with orchestrators (like Kubernetes), enabling automated scaling, rolling updates, and fault tolerance.
- Containers standardize development environments using tools like Docker Compose or dev containers.


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title: Differences between VM and Container?
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# Differences between VM and Containers?

::left::
## Virtual Machine
- Virtualizes hardware
- Runs a full guest OS (e.g., Linux or Windows)
- Heavier: includes the OS, libraries, and application
- Slow to start, uses more resources

**Example**: Running Ubuntu with Apache inside a VM on a Windows host

::right:: 

## Container
- Virtualizes at the OS level
- Shares the host OS kernel
- Isolates *only the application and its dependencies*
- Lightweight: faster startup, lower resource use

**Example:** Running a Node.js app in a container using the host's Linux kernel


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# How do they work?


## Containers are just processes

If you don't take anything else away from this talk, I hope you walk away with a better understanding of this fundamental.  As far as the OS* is concerned, a container is just another process/set of processes to the operating system.

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<p style="font-size:10px;max-width:20vw;line-height:1.3em;">*This is only strictly true on Linux.  Running Docker on Mac/Windows requires Docker Desktop which actually creates and manages a Linux VM.  Your containers actually run inside of this VM.</p>
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# Let's get started

::left::
## Windows/Mac
Install Docker Desktop from: https://docs.docker.com/desktop/

::right::
## Linux
Find installation instructions for Docker Engine here: https://docs.docker.com/engine/install/ubuntu/

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# Running our first container

## First run the container

We are running an nginx webserver container in daemon (background mode).  We are forwarding connections from localhost:8088 to port 80 *inside* the container.  This is the default port that nginx is running on.
````md magic-move
```shell
$ docker run --rm -p 8088:80 --name nginx-container -d nginx:alpine
```
```shell
$ docker run --rm -p 8088:80 --name nginx-container -d nginx:alpine
cd4302edce965beb95fdb9ecb19ff7432758f1e505d792e368fd401ea9abab65
```
```shell
$ docker container ps
```
```shell
$ docker container ps
CONTAINER ID   IMAGE          COMMAND                  CREATED          STATUS          PORTS                                     NAMES
cd4302edce96   nginx:alpine   "/docker-entrypoint.…"   15 seconds ago   Up 14 seconds   0.0.0.0:8088->80/tcp, [::]:8088->80/tcp   nginx-container
```
````

# Now run docker container ps to list running containers


<br />
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## View the logs for our container
````md magic-move

```shell
$ docker container logs --follow nginx-container 
```


```shell
$ docker container logs --follow nginx-container 
/docker-entrypoint.sh: /docker-entrypoint.d/ is not empty, will attempt to perform configuration
/docker-entrypoint.sh: Looking for shell scripts in /docker-entrypoint.d/
/docker-entrypoint.sh: Launching /docker-entrypoint.d/10-listen-on-ipv6-by-default.sh
10-listen-on-ipv6-by-default.sh: info: Getting the checksum of /etc/nginx/conf.d/default.conf
10-listen-on-ipv6-by-default.sh: info: Enabled listen on IPv6 in /etc/nginx/conf.d/default.conf
/docker-entrypoint.sh: Sourcing /docker-entrypoint.d/15-local-resolvers.envsh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/20-envsubst-on-templates.sh
/docker-entrypoint.sh: Launching /docker-entrypoint.d/30-tune-worker-processes.sh
/docker-entrypoint.sh: Configuration complete; ready for start up
2025/04/30 23:02:32 [notice] 1#1: using the "epoll" event method
2025/04/30 23:02:32 [notice] 1#1: nginx/1.27.5
2025/04/30 23:02:32 [notice] 1#1: built by gcc 14.2.0 (Alpine 14.2.0) 
2025/04/30 23:02:32 [notice] 1#1: OS: Linux 6.12.10-76061203-generic
2025/04/30 23:02:32 [notice] 1#1: getrlimit(RLIMIT_NOFILE): 1024:524288
2025/04/30 23:02:32 [notice] 1#1: start worker processes
2025/04/30 23:02:32 [notice] 1#1: start worker process 30
2025/04/30 23:02:32 [notice] 1#1: start worker process 31
2025/04/30 23:02:32 [notice] 1#1: start worker process 32
2025/04/30 23:02:32 [notice] 1#1: start worker process 33
2025/04/30 23:02:32 [notice] 1#1: start worker process 34
2025/04/30 23:02:32 [notice] 1#1: start worker process 35
2025/04/30 23:02:32 [notice] 1#1: start worker process 36
2025/04/30 23:02:32 [notice] 1#1: start worker process 37

```
````

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## Interacting with our container

Now let's try interacting with the Nginx server.  By default it should serve a default page.

````md magic-move

```shell
# Hitting Ctrl+Z on Linux will put our logs process into the background

$ ^Z
```
```shell
$ ^Z

[1]+  Stopped                 docker container logs --follow nginx-container
```
```shell
# Now send a curl request to localhost:8080.  This should be forwarded to port 80 in our container
$ curl localhost:8088
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
<style>
html { color-scheme: light dark; }
body { width: 35em; margin: 0 auto;
font-family: Tahoma, Verdana, Arial, sans-serif; }
</style>
</head>
<body>
<h1>Welcome to nginx!</h1>
<p>If you see this page, the nginx web server is successfully installed and
working. Further configuration is required.</p>

<p>For online documentation and support please refer to
<a href="http://nginx.org/">nginx.org</a>.<br/>
Commercial support is available at
<a href="http://nginx.com/">nginx.com</a>.</p>

<p><em>Thank you for using nginx.</em></p>
</body>
</html>
```
````