Add a couple of questions on containers

Also, fixed some minor styling issues in random_question.py script.

README.md

@@ -2,7 +2,7 @@
 
 :information_source:  This repo contains questions and exercises on various technical topics, sometimes related to DevOps and SRE :)
 
-:bar_chart:  There are currently **1825** questions
+:bar_chart:  There are currently **1840** questions
 
 :books:  To learn more about DevOps and SRE, check the resources in [devops-resources](https://github.com/bregman-arie/devops-resources) repository
 
@@ -6033,6 +6033,16 @@ It specifies the base layer of the image to be used. Every other instruction is
   * WORKDIR: sets the working directory inside the image filesystems for all the instructions following it
   * EXPOSE: exposes the specified port (it doesn't adds a new layer, rather documented as image metadata)
   * ENTRYPOINT: specifies the startup commands to run when a container is started from the image
+  * ENV: sets an environment variable to the given value
+  * USER: sets the user (and optionally the user group) to use while running the image
+</b></details>
+
+<details>
+<summary>What are some of the best practices regarding writing Dockerfiles that you are following?</summary><br><b>
+
+  * Include only the packages you are going to use. Nothing else.
+  * Specify a tag in FROM instruction. Not using a tag means you'll always pull the latest, which changes over time and might result in unexpected result.
+  * Do not use environment variables to share secrets
 </b></details>
 
 <details>
@@ -6333,6 +6343,16 @@ you with more options/features compared to Docker Hub. One example is
 Swarm management which means you can create new swarms in Docker Cloud.
 </b></details>
 
+#### Containers - Security
+
+<details>
+<summary>A container can cause a kernel panic and bring down the whole host. What preventive actions can you apply to avoid it?</summary><br><b>
+
+  * Install only the necessary packages in the container
+  * Set volumes and container's filesystem to read only
+  * DO NOT run containers with `--privilged` flag
+</b></details>
+
 #### Containers - Docker in Production
 
 <details>

exercises/devops/ci_for_open_source_project.md

@@ -9,4 +9,18 @@
 
 ### Bonus
 
-Containerize the app of the project you forked using any containerization technology you would like.
+Containerize the app of the project you forked using any container engine you would like (e.g. Docker, Podman).<br>
+Once you successfully ran the application in a container, submit the Dockerfile to the original project (but be prepared that the maintainer might not need/want that).
+
+### Suggestions for Projects
+
+The following is a list of projects without CI (at least at the moment):
+
+Note: I wrote a script to find these (except the first project on the list, of course) based on some parameters in case you wonder why these projects specifically are listed.
+
+* [This one](https://github.com/bregman-arie/devops-exercises) - We don't have CI! help! :)
+* [image retrieval platform](https://github.com/skx6/image_retrieval_platform)
+* [FollowSpot](https://github.com/jenbrissman/FollowSpot)
+* [Pyrin](https://github.com/mononobi/pyrin)
+* [food-detection-yolov5](https://github.com/lannguyen0910/food-detection-yolov5)
+* [Lifely](https://github.com/sagnik1511/Lifely)

exercises/devops/containerize_app.md

@@ -6,18 +6,9 @@
 https://github.com/bregman-arie/node-hello-world
 https://github.com/bregman-arie/flask-hello-world
 ```
-
-`git clone https://github.com/bregman-arie/node-hello-world`
-
 2. Write a Dockerfile you'll use for building an image of the application (you can use any base image you would like)
-
-```
-FROM alpine
-LABEL maintainer="your name/email"
-RUN apk add --update nodejs nodejs-npm
-COPY . /src
-WORKDIR /src
-RUN npm install
-EXPOSE 8080
-ENTRYPOINT ["node", "./app.js"]
-```
+3. Build an image using the Dockerfile you've just wrote
+4. Verify the image exists
+5. [Optional] Push the image you've just built to a registry
+6. Run the application
+7. Verify the app is running

exercises/devops/solutions/containerize_app.md

@@ -0,0 +1,54 @@
+## Containerize an Application
+
+1. Clone an open source project you would like to containerize. A couple of suggestions:
+
+```
+https://github.com/bregman-arie/node-hello-world
+https://github.com/bregman-arie/flask-hello-world
+```
+
+`git clone https://github.com/bregman-arie/node-hello-world`
+
+2. Write a Dockerfile you'll use for building an image of the application (you can use any base image you would like)
+
+```
+FROM alpine
+LABEL maintainer="your name/email"
+RUN apk add --update nodejs npm
+COPY . /src
+WORKDIR /src
+RUN npm install
+EXPOSE 3000
+ENTRYPOINT ["node", "./app.js"]
+```
+
+3. Build an image using the Dockerfile you've just wrote
+
+`docker image build -t web_app:latest .`
+
+4. Verify the image exists
+
+`docker image ls`
+
+5. [Optional] Push the image you've just built to a registry
+
+```
+docker login
+docker image tag web_app:latest <your username>/web_app:latest
+# Verify with "docker image ls"
+docker image push <your username>/web_app:latest
+```
+
+6. Run the application
+
+```
+docker container run -d -p 80:3000 web_app:latest
+```
+
+7. Verify the app is running
+
+```
+docker container ls
+docker logs <container ID/name>
+# In the browser, go to 127.0.0.1:80
+```

scripts/random_question.py

@@ -3,48 +3,51 @@
 
 
 def main():
-    """ Reads through README.md for question/answer pairs and adds them to a list to randomly select from and quiz yourself. 
-        - supports skipping quesitons with no documented answer with the -s flag
+    """Reads through README.md for question/answer pairs and adds them to a
+    list to randomly select from and quiz yourself.
+    Supports skipping quesitons with no documented answer with the -s flag
     """
     parser = optparse.OptionParser()
-    parser.add_option("-s", "--skip", action="store_true",help="skips questions without an answer.", default=False)
+    parser.add_option("-s", "--skip", action="store_true",
+                      help="skips questions without an answer.",
+                      default=False)
     options, args = parser.parse_args()
-    
+
     with open('README.md', 'r') as f:
         text = f.read()
-        
+
     questions = []
-    
+
     while True:
         question_start = text.find('<summary>') + 9
         question_end = text.find('</summary>')
         answer_end = text.find('</b></details>')
-        
+
         if answer_end == -1:
             break
-        
+
         question = text[question_start: question_end].replace('<br>', '').replace('<b>', '')
         answer = text[question_end + 17: answer_end]
         questions.append((question, answer))
         text = text[answer_end + 1:]
-        
+
     num_questions = len(questions)
-    
+
     while True:
         try:
             question, answer = questions[random.randint(0, num_questions)]
-            
+
             if options.skip and not answer.strip():
                 continue
-            
+
             if input(f'Q: {question} ...Show answer? "y" for yes: ').lower() == 'y':
                 print('A: ', answer)
-        
+
         except KeyboardInterrupt:
             break
-        
+
     print("\nGoodbye! See you next time.")
-                
+
 
 if __name__ == '__main__':
     main()