Simple Docker

Introduction to docker. Developing a simple docker image for your own server.

The russian version of the task can be found in the repository.

Contents

1. Chapter I
2. Chapter II
   2.1. nginx
   2.2. Docker
   2.3. Dockle
3. Chapter III
   3.1. Ready-made docker
   3.2. Operations with container
   3.3. Mini web server
   3.4. Your own docker
   3.5. Dockle
   3.6. Basic Docker Compose

Chapter I

Planet Earth, Atlantic Ocean, Her Majesty's Ship "Hood", heading to London, UK, nowadays.

You never liked moving. A lot of fuss, little action. But you managed to find a great job to delve into DevOps world in Foggy Albion. And you're not one to let minor difficulties ruin your plans.

From your cabin window you hear the sound of the waves, the ship is peacefully rocking on them and you remember your favorite novel about the sea - "Moby Dick". Although the flow of the plot is far from straightforward, with many lyrical digressions and philosophical musings, you, like everyone else, associate this book primarily with Moby Dick himself - the white whale.

"Hmm... White whale..." - here you remember that during the long journey you were going to work on docker.

Chapter II

nginx

nginx (pronounced "engine-x") is an open-source reverse proxy server for HTTP, HTTPS, etc. nginx is also used as a load balancer, web server and for HTTP caching. The nginx project focuses on high parallelism, high performance and low memory usage.

nginx has one main process and several worker processes. The primary task of the main process is to read and check the configuration and manage the worker processes. The worker processes perform the actual processing of the requests.

How nginx and its modules work is defined in the configuration file. By default, the configuration file is called nginx.conf

Docker

A container is a new "executable file" that includes all the dependencies the product needs.

The main advantage of containerisation is the isolation of dependencies and a single, simple software start-up point.

Basic terms:

• Docker image - the "package" for the application and dependencies (including system ones).
• Container - an instance of an image, i.e. a 'alive' image.

Docker is a platform that is designed to develop, deploy and run applications in containers. Docker is the 'de-facto' standard containerisation tool in the industry, but it is not the first or last among containerisation technologies.

The forerunners of Docker containers were virtual machines. A virtual machine, like a container, isolates the application and its dependencies from the outside environment. However, Docker containers have advantages over virtual machines. For example, they are very easy to port, consume fewer resources, start and run faster.

A docker image consists of layers. Each layer describes some change to be performed to the data on the running container. The structure of links between layers is hierarchical. There is a base layer on which the other layers are "overlaid". The Dockerfile is used to create an image. Each instruction in it creates a new layer.

Dockle

Dockle is a container image security checking tool that can be used to find vulnerabilities.

Key features and benefits of Dockle:

• searches for vulnerabilities in images
• helps in creating a proper Dockerfile
• easy to use, you only need to specify the image name
• support for CIS Benchmarks.

Docker Compose

Docker Compose is a tool for handling tasks related to projects deployment. Docker Compose can be helpful if several services are used to keep the project running.

Docker Compose is used to simultaneously manage multiple containers that are part of an application. This tool offers the same features as Docker, but allows to work with more complex distributed applications, e.g. microservices.

Chapter III

As a result of the work you should provide a report on the first two tasks. Each part of the task describe what should be added to the report once it has been completed. This can be answers to questions, screenshots, etc.

As a result of the third task you should provide source files for running the web server.

As a result of the fourth and fifth tasks you should provide dockerfiles.

As a result of the sixth task you should provide a docker-compose.yml file and the dockerfiles needed to run it (if not provided earlier).

• A report with a .md extension must be uploaded to the repository, in the src folder.
• All parts of the task should be highlighted in the report as level 2 headings.
• Within one part of the task, everything that is added to the report must be in the form of the list.
• Each screenshot in the report must be briefly captioned (what’s in the screenshot).
• All screenshots must be cropped so that only the relevant part of the screen is shown.
• It’s allowed to have several task points shown in one screenshot, but they must all be described in the caption.
• Source files for running the web server from the third task should be uploaded to the repository, in the src/server folder.
• Dockerfiles from the fourth and fifth tasks should be uploaded to the repository, in the src folder.
• docker-compose.yml from the sixth task should be uploaded to the repository, in the src folder.
• Be prepared to demonstrate your work if necessary.

Part 1. Ready-made docker

As the final goal of your little practice you have immediately chosen to write a docker image for your own web server, so first you need to deal with a ready-made docker image for the server. You chose a pretty simple nginx.

== Task ==

Take the official docker image from nginx and download it using docker pull.

Check for the docker image with docker images

Run docker image with docker run -d [image_id|repository]

Check that the image is running with docker ps

View container information with docker inspect [container_id|container_name]

From the command output define and write in the report the container size, list of mapped ports and container ip

Stop docker image with docker stop [container_id|container_name]

Check that the image has stopped with docker ps

Run docker with ports 80 and 443 in container, mapped to the same ports on the local machine, with run command

Check that the nginx start page is available in the browser at localhost:80

Restart docker container with docker restart [container_id|container_name]

Check in any way that the container is running

• Add the following screenshots to the report:
  • the call and output of all commands used in this part of the task;
  • nginx start page at localhost:80 (address must be shown).

Note: Don't upload heavy files (>10 mb) to git.

Part 2. Operations with container

Docker image and container are ready. Now we can look into nginx configuration and display page status.

== Task ==

Read the nginx.conf configuration file inside the docker container with the exec command

Create a nginx.conf file on a local machine

Configure it on the /status path to return the nginx server status page

Copy the created nginx.conf file inside the docker image using the docker cp command

Restart nginx inside the docker image with exec

Check that localhost:80/status returns the nginx server status page

Export the container to a container.tar file with the export command

Stop the container

Delete the image with docker rmi [image_id|repository]without removing the container first

Delete stopped container

Import the container back using the importcommand

Run the imported container

Check that localhost:80/status returns the nginx server status page

• Add the following screenshots to the report:
  • the call and output of all commands used in this part of the task;
  • the contents of the created nginx.conf file;
  • the nginx server status page at localhost:80/status.

Part 3. Mini web server

It's time to take a little break from the docker to prepare for the last stage. It's time to write your own server.

== Task ==

Write a mini server in C and FastCgi that will return a simple page saying Hello World!

Run the written mini server via spawn-fcgi on port 8080

Write your own nginx.conf that will proxy all requests from port 81 to 127.0.0.1:8080

Check that browser on localhost:81 returns the page you wrote

Put the nginx.conf file under ./nginx/nginx.conf (you will need this later)

Part 4. Your own docker

Now everything is ready. You can start writing the docker image for the created server.

== Task ==

When writing a docker image avoid multiple calls of RUN instructions

Write your own docker image that:

1) builds mini server sources on FastCgi from [Part 3](#part-3-mini- web-server)

2) runs it on port 8080

3) copies inside the image written ./nginx/nginx.conf

4) runs nginx.

nginx can be installed inside the docker itself, or you can use a ready-made image with nginx as base.

Build the written docker image with docker build, specifying the name and tag

Check with docker images that everything is built correctly

Run the built docker image by mapping port 81 to 80 on the local machine and mapping the ./nginx folder inside the container to the address where the nginx configuration files are located (see Part 2)

Check that the page of the written mini server is available on localhost:80

Add proxying of /status page in ./nginx/nginx.conf to return the nginx server status

Restart docker image

*If everything is done correctly, after saving the file and restarting the container, the configuration file inside the docker image should update itself without any extra steps

Check that localhost:80/status now returns a page with nginx status

Part 5. Dockle

Once you've written the image, it's never a bad idea to check it for security.

== Task ==

Check the image from the previous task with dockle [image_id|repository]

Fix the image so that there are no errors or warnings when checking with dockle

Part 6. Basic Docker Compose

There, you've finished your warm-up. Wait a minute though... Why not try experimenting with deploying a project consisting of several docker images at once?

== Task ==

Write a docker-compose.yml file, using which:

1) Start the docker container from Part 5 (it must work on local network, i.e., you don't need to use EXPOSE instruction and map ports to local machine)

2) Start the docker container with nginx which will proxy all requests from port 8080 to port 81 of the first container

Map port 8080 of the second container to port 80 of the local machine

Stop all running containers

Build and run the project with the docker-compose build and docker-compose up commands

Check that the browser returns the page you wrote on localhost:80 as before

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