Update

exercises/containers/image_layers.md

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+## Layer by Layer
+
+### Objective
+
+Learn about image layers
+
+### Requirements
+
+Make sure Docker is installed on your system and the service is started
+
+```
+# Fedora/RHEL/CentOS
+rpm -qa | grep docker
+systemctl status docker
+```
+
+### Instructions
+
+1. Write a Dockefile. Any Dockefile! :) (just make sure it's a valid one)
+2. Build an image using the Dockerfile you've wrote
+3. Which of the instructions you've used, created new layers and which added image metadata?
+4. What ways are there to confirm your answer to the last question?
+5. Can you reduce the size of the image you've created?

exercises/containers/solutions/image_layers.md

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+## Layer by Layer
+
+### Objective
+
+Learn about image layers
+
+### Requirements
+
+Make sure Docker is installed on your system and the service is started
+
+```
+# Fedora/RHEL/CentOS
+rpm -qa | grep docker
+systemctl status docker
+```
+
+### Instructions
+
+1. Write a Dockefile. Any Dockefile! :) (just make sure it's a valid one)
+
+```
+FROM ubuntu
+EXPOSE 212
+ENV foo=bar
+WORKDIR /tmp
+RUN dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024
+RUN dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024
+RUN dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024
+```
+
+2. Build an image using the Dockerfile you've wrote
+
+`docker image build -t super_cool_app:latest .`
+
+3. Which of the instructions you've used, created new layers and which added image metadata?
+
+```
+FROM, RUN -> new layer
+EXPOSE, ENV, WORKDIR -> metadata
+```
+
+4. What ways are there to confirm your answer to the last question?
+
+You can run `docker image history super_cool_app`. It will show you each instruction and its size. Usually instructions that create new layers has non-zero size, but this is not something you can rely on by itself since, some run commands can have size of zero in `docker image history` output (e.g. `ls -l`).
+
+You can also use `docker image inspect super_cool_appl` and see if in the output, under "RootFS", there are the number of layers that matches the instructions that should create new layers.
+
+5. Can you reduce the size of the image you've created?
+
+yes, for example, use all the RUN instructions as a single RUN instruction this way:
+
+`RUN dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024 && dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024 && dd if=/dev/zero of=some_file bs=1024 count=0 seek=1024`
+
+The change in size might not be dramatic in this case, but in some cases it will make a big impact on the image size.

exercises/devops/ha_hello_world.md

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+## Highly Available "Hello World"
+
+Set up an highly available "Hello World" application with the following instructions:
+
+* Use a containerized Load Balancer
+* Provision two virtual machines (this is where the app will run)
+* The page, when visited, should show "Hello World! I'm host X" - X should be the name of the virtual machine

exercises/devops/solutions/ha_hello_world.md

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+## Highly Available "Hello World"
+
+Set up an highly available "Hello World" application with the following instructions:
+
+* Use a containerized Load Balancer
+* Provision two virtual machines (this is where the app will run)
+* The page, when visited, should show "Hello World! I'm host X" - X should be the name of the virtual machine
+
+### Solution
+
+1. Provision two VMs