Step 3: Load a Simple Docker Project

Snap applications are easy to install because they take care of all of the dependencies and run it in a semi-isolated environment.

  • One drawback is one that the application is tightly integrated. Configuring it or modifying it to use a different component is hard to do.

  • It’s not practical to use snaps to run part of the application one box and then have the database on another server.

Docker containers address these problems. Like snaps, Docker containers run in isolation, meaning they will not conflict with services running on the host machine.

  1. For this step, we will run the Docker-based application in a similar fashion to how snaps operate.

  2. We still have the problem of one application per box, but this moves us closer to distributed computing because Docker lets developers spread or distribute the components across different containers.

This Docker project works in isolation. It is a single container that contains the web server, database, and all of the data.

Installing NextCloud on Docker

Nextcloud is an open source tool for cloud storage. It has web, desktop, and mobile applications.

  • This installation is for demonstration purposes only.

  • We will do a production-ready install later so you can use to store your data in the cloud

We’ll use the instruction from https://github.com/nextcloud/docker to run NextCloud in Docker.

  1. Run the Docker container

    • The command has these arguments:

      run -d

      Runs the container in daemon mode, which means running it in the background

      -p 20850:80

      The port pairs.

      • The first port (20850) is the external port, which is accessible to the VPS.

      • The second port (80) is internal to the Docker container.

      nextcloud

      Name of the container to run. This container is pulled from Docker Hub.

    docker run -d -p 20850:80 nextcloud
    
    Output
    root@vps298933:~# docker run -d -p 20850:80 nextcloud
    Unable to find image 'nextcloud:latest' locally
    latest: Pulling from library/nextcloud
    f7e2b70d04ae: Pull complete
    744aedb7995c: Pull complete
    07afe22f8a58: Pull complete
    c7bf4f31c4a4: Pull complete
    b528e75732cc: Pull complete
    27e7d214ded2: Pull complete
    894549c23c16: Pull complete
    9aa6d55932b2: Pull complete
    1b27fd7479e6: Pull complete
    eacdac7d65c9: Pull complete
    66f1bd2ad7cf: Pull complete
    ee6444380c18: Pull complete
    1500f6dd9b69: Pull complete
    18560f19c8c4: Pull complete
    bddc5d1da8e7: Pull complete
    6e33450d197c: Pull complete
    6f195f51537c: Pull complete
    a8c28fabf19a: Pull complete
    ad044e6f6c56: Pull complete
    20144f3a754f: Pull complete
    Digest: sha256:4c3a690b1771ba414c0a347514baae52dae3ec34feb747d5db0c4188d8462562
    Status: Downloaded newer image for nextcloud:latest
    0b3091ea59c416ce8c2dc1fbdbce960ce3c1164e53d2c6fc440222c059abc10a
    root@vps298933:~#
    
  2. Let’s verify that it is running using docker ps

    docker ps

    List all running containers

    docker ps -a

    List all running and stopped containers

    Output
    root@vps298933:~# docker ps
    CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS                  NAMES
    f09da32f5217        nextcloud           "/entrypoint.sh apac…"   9 minutes ago       Up 9 minutes        0.0.0.0:20850->80/tcp   hardcore_bhaskara
    root@vps298933:~#
    

    If you do not see it, then run docker ps -a to see if it tried to start, but then failed. If it did not start correctly, then stop and remove it.

    • Steps to stopping and removing a running container:

      1. docker stop <Container ID>

      2. docker rm <Container ID>

  3. Let’s verify that the application will respond to a web request using curl.

    curl localhost:20850
    
    Output
    root@vps298933:~# curl localhost:20850
    <!DOCTYPE html>
    <html class="ng-csp" data-placeholder-focus="false" lang="en" data-locale="en" >
            <head data-requesttoken="utvzF1Gkzv92ZJIBFqsjSLd3adMzlGsTqkDz1IHAs2c=:y5GmUDz1/ok0CaBDW8wIcY4lC6Bf5iNg8g6crbeu9VI=">
                    <meta charset="utf-8">
                    <title>
                    Nextcloud               </title>
                    <meta http-equiv="X-UA-Compatible" content="IE=edge">
                    <meta name="referrer" content="no-referrer">
                    <meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0">
                    <meta name="apple-itunes-app" content="app-id=1125420102">
                    <meta name="theme-color" content="#0082c9">
                    <link rel="icon" href="/core/img/favicon.ico">
                    <link rel="apple-touch-icon-precomposed" href="/core/img/favicon-touch.png">
                    <link rel="mask-icon" sizes="any" href="/core/img/favicon-mask.svg" color="#0082c9">
    .
    .
    .