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technology/tools/Docker.md

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+---
+website: https://www.docker.com/
+obj: application
+---
+
+#refactor
+---
+Notes:
+- Docker (CLI)
+- Dockerfile
+- Docker Swarm
+---
+
+# Docker
+[Docker](https://www.docker.com/) is a utility to pack, ship and run any application as a lightweight container. Another container engine is [Podman](Podman.md)
+
+## Dockerfile
+Every container can be build from a `Dockerfile`.
+
+### Example
+A sample `Dockerfile`:
+```dockerfile
+FROM node:12-alpine
+RUN apk add --no-cache python2 g++ make
+WORKDIR /app
+COPY . .
+RUN yarn install --production
+CMD ["node", "src/index.js"]
+EXPOSE 3000
+```
+
+`FROM` defines the base image the container builds upon.
+`RUN` runs a specific command.
+`WORKDIR` changes working directory.
+`COPY` copies files into the container image.
+`CMD` is run when the container starts.
+`EXPOSE` exposes a port to the network.
+`ENV` sets environment variables
+`ENTRYPOINT` specifies the executable that will run when the container starts
+`ARG` defines build-time variables that can be passed to the `docker build` command with the `--build-arg` flag
+
+To build a `Dockerfile`:
+```shell
+docker build -t getting-started .
+```
+
+## Docker Compose
+[Docker Compose](https://docs.docker.com/compose/) is an alternate CLI frontend for the Docker Engine, which specifies properties of containers using a `docker-compose.yml` YAML file rather than, for example, a script with `docker run` options. This is useful for setting up reoccuring services that are use often and/or have complex configurations.
+
+### Example
+```yaml
+version: "3.7"
+
+services:
+  app:
+    build: ./app
+    ports:
+      - 3000:3000
+    volumes:
+      - ./:/app
+    environment:
+      MYSQL_HOST: mysql
+      MYSQL_USER: root
+      MYSQL_PASSWORD: secret
+      MYSQL_DB: todos
+
+  mysql:
+    image: mysql:5.7
+    volumes:
+      - todo-mysql-data:/var/lib/mysql
+    environment:
+      MYSQL_ROOT_PASSWORD: secret
+      MYSQL_DATABASE: todos
+```
+
+Every container is defined within the `services`.
+Ports Forwards and Volumes are defined in their respective `ports` and `volumes`.
+Everything inside `environment` is passed as a environment variable.
+Containers can use a prebuild image (`image: image:tag`) or build one from scratch (`build: ./dir`)
+
+### Usage
+```shell
+docker-compose -f docker-compose.yml up    # Start services
+docker-compose -f docker-compose.yml down  # Stop services
+docker-compose -f docker-compose.yml build # Rebuild services
+docker-compose -f docker-compose.yml pull  # Pull images
+```
+
+## Docker Swarm
+Current versions of Docker include _swarm mode_ for natively managing a cluster of Docker Engines called a _swarm_. Use the Docker CLI to create a swarm, deploy application services to a swarm, and manage swarm behavior.
+
+### Usage
+```shell
+# Create a swarm
+docker swarm init --advertise-addr <MANAGER-IP>
+
+# Get a join command on manager
+docker swarm join-token worker
+
+# Join a swarm
+docker swarm join --token <TOKEN> <MANAGER-IP>:2377
+
+# View node info
+docker node ls
+```