# Docker

_General Knowledge_ ### What does it mean to "Deploy" a server/service?

> "Deploying" a server means to make it available for consumption. Some of these tasks include: * Downloading necessary files to a server (usually a Linux-based one) * Setting up configuration files * Configure networking (ports, firewalls) * Running processes (i.e. Running the app itself)

### What are some of the challenges found here?

* Complicated processes that normally involve dozens of commands * Issues with inconsistencies between environments * OS Incompatibility * Incorrect dependency versions * Issues with reproducing errors that occur on a specific environment

### What are containers? > 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.

#### Containers vs. Virtual Machines <img src="img/vm.png"/>

#### How do containers help developers? * Consistency of environments * Quick & easy setup * Freedom to make mistakes

#### How does it help companies * Cut down development time * More resource-efficient === more \$\$\$ * Less resources used to fix edge cases * Uniform/Centralized method of deployment (means less complexity)

##### Bonus Section: Container deployment and management with Rancher! * https://rancher.com

_Dev Lecture_ ### Dockerfiles and images

#### Dockerfile * Dockerfiles are recipe books to build and deploy images * Usual flow: 1. Create `Dockerfile` 2. Build images 3. Run as many containers as needed

[Dockerfile](https://docs.docker.com/engine/reference/builder/) ``` # Choosing image from docker hub registry FROM nginx:latest # Making sure port 80 is available from container EXPOSE 80 # Copy pre-made nginx configuration file into container COPY config/nginx.conf /etc/nginx/nginx.conf # Copying built project into nginx directory COPY ./build/* /var/www/ # Start up nginx server RUN nginx ```

#### Images * Images are pre-made packages that contain all necessary files * Files included are defined in the Dockerfile * You have the freedom to set environment variables & bind volumes at run-time

### Building your own image

``` docker build -t {image_name} . ```

### Running your first container

``` docker run -p 80:80 --name {container_name} {image_name} ```