CPE434-Lab 13 Docker Containers Solved

Dockers or containers are tools that help you to create and deploy applications with ease. This means, you can package up the parts that are needed for the applications to run without worrying about the systems at the users' side or deployment site. Containers are somewhat similar to virtual machines, but instead of requiring a complete OS as in virtual machine, you will perform OS virtualization.

In this lab, you will see an example where we will write a program that has different dependencies that are not installed in the deployment machine.

Procedures
Log into the echo sever, and then log into your assigned odroid as an odroid user. The first thing we are going to do is verify if you have sudo user access.

 

Inorder to verify you have sudo user access, please perform the following command. You will use su command followed by the username.

 

Now that you have verified you have sudo access, things will be easier.

Although we have not installed docker on our machine, let us verify one last time. Please type docker in your terminal. You should see a command not found or something of that sort.

Assignment 1: Installation of Docker on ARM machine
Following contents are derived from official docker website at Install Docker Engine on Ubuntu | Docker Documentation. If you have any problems during the installation process, please visit the link.

The machine that we are using is odroid, which is an ARM machine. You can type cat /proc/cpuinfo to see the processor information of the machine that you are using. We also need to find out the OS version that we are using. Please use the following commands and answer the questions that follows:

lsb_release -a uname -a

1.  What is the OS name and version in your machine?

2.  What is the kernel version in your machine?

3.  How many processors are there in your machine and what are their model names?

We need to remove docker, if there is any, before moving forward. So, please do the following in your terminal.

Please follow as it shows in the image below:

 

Now, let us update. sudo apt-get update

You might see some warnings, but ignore them for now. let us move forward with some installations.

sudo apt-get install \ apt-transport-https \ ca-certificates \ curl \

gnupg-agent \

software-properties-common

This will take some time to complete, but there should be no problem to install.

Now we will add docker's official GPG key:

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add - , which should report you OK,

but we will verify that using the following command.

sudo apt-key fingerprint 0EBFCD88

This should show you some installed keys.

Now is the main part where we will add the link to the repository of docker release based on our linux version and architecture of hardware we are using. Please use the following command:

sudo add-apt-repository \

"deb [arch=armhf] https://download.docker.com/linux/ubuntu \

$(lsb_release -cs) \ stable"

Now you have set up the repository. We will update once again, and install docker on our machine. sudo apt-get update sudo apt-get install docker-ce docker-ce-cli containerd.io

You might get similar messages while updating but you can ignore them again. Continue with the installation with the second command above. This will again take some time to complete.

Assignment 2: Verify Docker Installation
Now that docker is installed properly, we have to verify installation. Please run the following:

sudo docker run hello-world

This will download an image and run it in a container. Please run this command, take a screenshot and read the contents of the output that you see.

Program and Dependency
Following is the program that has some different dependency.

# file: myPython2.py import sys

def python2_stuff():

print("Yeah!!! This is function called only by python2.x") print("This is an important function")

if sys.version_info[0]<3:

print("This will only work with python version 2.x") python2_stuff()

else:

print("Error!!!You are not supposed to run it like this.")
If you run this with python2, you will make a call to the function python2_stuff(). If you run with python3, the function will not be called. We want the function to be called because that is an important function. Please run this code using python2 myPython2.py

Let us remove python2 from our machine. Please use the following command to remove python 2.7.

sudo apt purge python2.7-minimal

This will take some time and will remove python2.7

Now, try running the code again using python2. Do you notice any difference?

Assignment 3: Running using a container
You only have python3 in your machine, but let us assume that a software that you wrote is in python2. You might be in a situation like this when you inherit a large software code base written in python2. Or in a different situation when you bought a software that is written in python2, but you are not allowed to install python2 on your machine due to company policy. The worst situation is when you do not know what dependencies are being used, or you do not want your customer to install dependencies and want to make things easier for them. A docker image can be created to manage and install any missing dependencies required while creating the image, and these dependencies are irrespective of what is installed in the machine.

Please run the following command: sudo docker run prawar/lab14_demo:public_student

This will take some time to run. What docker run command does is it searches for the image by the name prawar/lab14_demo:public-student locally. If it does not find it in the local machine, as in our case, it downloads the image from docker hub and runs it. This is what it does for the first time you run it. Take a screenshot of the output and confirm if the output is the same as what you saw before you uninstalled python2.

If you run the command again, it will not download. But it runs the local image. Please put a screenshot of the same.

Assignment 4: Creating Docker Image
For the assignment above, someone had already built an image and we ran as a customer. But what if we are software developers and want to release a software but do not want customers to go through the hassle of installing all the dependencies ? We have to create a docker image and release it in public.

The docker image requires at least two files. One is called Dockerfile and the other is your source file. You can create other files based on your need, but we will create a minimal example for demonstration purposes. Dockerfile is the one that specifies all the commands a user will require to build an image. We will base our image on python2 so there is not much package installation that we need to do. But you can install other libraries and packages using RUN instruction in the Dockerfile.

1.  Create a new directory named myDocker

2.  Go inside the folder that you just created. This will be our directory for docker files that we need for our image.

3.  Create a text file named Dockerfile and add the following contents in the file.

 

The commands in the file use python2.7 as the base for our image. it sets up /app as the working directory and copies the content of this current folder to /app.

Save the file.

5.     The above file also mentions that the image should run python myPython2.py. Copy the code that runs for python2 from Assignment2 to the current folder (i.e. to the folder myDocker)

6.     If your source file myPython2.py contains any other dependencies, you can install them using RUN command in the Dockerfile.

7.     Build the image using the following command sudo docker build --tag=mylab14_<yourchargerID . .Replace yourchargerID with your charger id. Donot forget the '.' after a space after your charge id. This will take some time to run and you will get something like the following.

 

8.     Perform docker image ls to see the images that are in your machine. You should see the image that you just created also.

9.     Run the image that you just created using sudo docker run mylab14_<yourchargerID.

10.  Go to hub.docker.com and create an account for you. After you have created an account, go to your working terminal and login using sudo docker login.

11.  You will make this image available publicly, and download again to run it in your machine. You need to tag it first. So what you will do is tag your repository using sudo docker tag mylab14_<yourchargerID <yourusernameindockerhub/lab14_public:<yourchargerID.

12.  Perform sudo docker image ls to see all the local repositories that you have. You should see a new one with the new tag. For the image that you created, what are the following values?

1.  Image name

2.  TAG

3.  image id

4.  size

13.  Push this image to the docker hub using sudo docker push

<yourusernameindockerhub/lab14_public:<yourchargerID. After this operation is completed, go to your account in the docker hub and verify that it is available there.

Assignment 5: Distribution
1. Now that you have created a software that runs regardless of the dependencies available in the user machine, you would want to distribute it. Find at least one customer of your software (you can find a friend in CPE435) and tell them to download the image as you did in Assignment 3. Ask a screenshot from them of the final run and post it in your report.