Docker

- Installing docker
  https://itsfoss.com/install-docker-arch-linux/

- Configuration
  - Add user to docker group
  `sudo usermod -aG docker $USER`
  - Log out and Log Back In
After adding your user to the Docker group, you need to either log out and log back in or reboot your system. This step is necessary for the group changes to take effect. An alternative is to use the following command to apply the group change immediately:
`newgrp docker`

  - If again needed a permission then 
    - Check Docker Daemon Permissions
`ls -l /var/run/docker.sock`
The output should show that the group is set to docker. If not, you can adjust the permissions with:
`sudo chown root:docker /var/run/docker.sock`


  
- To list images use
  `docker images`
- To list containers use
  `docker ps`
  
- To delete container or image forcefully respectively
  `docker rm -f <container_id>` and `docker rmi -f <images_id>`
- Issues
  https://stackoverflow.com/questions/51188657/image-is-being-used-by-stopped-container-error
 building image:
    
    `docker build -t username/first_app:1.0`
    
    it will produce an output and will produce image starting with sha……
    
    To run the image use:  
    `docker run <image_name/code>`
    
    Now if we try to run it with port(here in eg port is 8080) then it wont run because by default its not accessible outside container so to expose it we can use port forwarding.
    
    `docker run -p 5000:8080 <image_name/code>`
    
    port 8080 of container is forwarded to port 5000 of outside container. 5000:8080 is mapping
    
    - For publishing
        
        Now login through the CLI by executing:
        
```
        docker login
```
        
        Push your Docker Image to the Docker Hub repository with the following command:
        
```
        docker image push <repository>/<image>:<tag>
```
        
        Example:
        
   ```
        docker image push dhanushkamath/dockerize-node:1.0.0
   ```
        
        You’ve successfully published your first image to the world!
        
        Running this container on a different computer that has Docker only requires a single command:
        
  ```
    docker run dhanushkamath/dockerize-node:1.0.0
   ```
 - Reducing image size
   https://devopscube.com/reduce-docker-image-size/
 &nbsp;
 
 **Dockerhub**
  Anonymous and Free Docker Hub users are limited to 100 and 200 container image pull requests per six hours.
  ![764c7f377091033262190448212db4e5.png](../../../_resources/764c7f377091033262190448212db4e5.png)
  &nbsp;
  When using docker login the auth token will be stored in `SHOME/.docker/config.json` so using different users we can login to different accounts simuntaneously
  &nbsp;
  **Pushing images to dockerhub**
  - When we create image using `docker build -t image_name:tagname .` then we get a image of name specified. To push image in dockerhub, image name should be in format `username/repo:tagname` . So instead of creating image again with same format we can create a link/tag to local image with
   `docker tag local_image_name:tagname username/repo_name:tagname`. so for same image we have 2 different names. Now we can just push with
   `docker image push username/repo_name:tagname`
   Then finally to download it use
   `docker pull username/repo_name:tagname`
&nbsp;

### Docker container with multiple node instances
- Use pm2 for it 
  Structure of files in host
  ```text
	puppetter_test
		index.js
		ecosystem.config.js
		... (other files)
	ytDownloadSpace
		app.js
		... (other files)
	ytdlApi
		app.js
		... (other files)
	Dockerfile
  ```
  Dockerfile
  ```yaml
 	FROM alpine
	RUN apk add --update nodejs npm bash

	# App 1
	WORKDIR /src/puppetter_test
	COPY puppetter_test/ ./
	RUN npm install

	# App 2
	WORKDIR /src/ytDownloadSpace
	COPY ytDownloadSpace ./
	RUN npm install


	# App 3
	WORKDIR /src/ytdlApi
	COPY ytdlApi/ ./
	RUN npm install




	RUN npm install -g pm2

	#config file
	WORKDIR /src/puppetter_test
	EXPOSE 8081
	# starting pm2 with --no-daemon flag to keep it running in foreground
	# instead of background to prevent docker container from stopping
	CMD pm2 start ecosystem.config.js --no-daemon



  ```
  
  `ecosystem.config.js`
  ```js
  module.exports = {
	  apps: [
		{
		  name: 'main',
		  script: 'index.js',
		  watch: true,
		  env: {
			NODE_ENV: 'production',
			PORT: 8081
		  }
		},
		{
		  name: 'ytdownloadspace',
		  script: '../ytDownloadSpace/app.js',
		  watch: true,
		  env: {
			NODE_ENV: 'production',
			PORT: 8080
		  }
		},
		{
		  name: 'ytdlApi',
		  script: '../ytdlApi/app.js',
		  watch: true,
		  env: {
			NODE_ENV: 'production',
			PORT: 8083
		  }
		}
	  ]
  };

	```
- docker import and export images
  https://stackoverflow.com/questions/24482822/how-to-share-my-docker-image-without-using-the-docker-hub
 Based on this blog, one could share a docker image without a docker registry by executing:
`docker save --output latestversion-1.0.0.tar dockerregistry/latestversion:1.0.0`
Once this command has been completed, one could copy the image to a server and import it as follows:
`docker load --input latestversion-1.0.0.tar`