Virtualization and containers concept in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is virtualization in computing?

Virtualization is a technology that lets one physical computer act like many separate computers by creating virtual machines. Each virtual machine runs its own operating system and applications independently.

intermediate

How do containers differ from virtual machines?

Containers share the host computer's operating system kernel but isolate applications in separate spaces. Virtual machines include a full operating system each, making them heavier than containers.

beginner

What is a real-world analogy for virtualization?

Think of virtualization like an apartment building. The building is the physical computer, and each apartment is a virtual machine. Each apartment has its own rooms (OS and apps), but they all share the building's structure.

intermediate

Why are containers considered lightweight?

Containers are lightweight because they share the host OS kernel and only package the application and its dependencies, unlike virtual machines which include a full OS each.

beginner

What is the main benefit of using virtualization or containers?

They allow better use of hardware by running multiple isolated environments on one physical machine, saving cost and improving flexibility.

Which of the following best describes a virtual machine?

A A full operating system running on virtualized hardware

B An application sharing the host OS kernel

C A physical computer

D A type of container

A virtual machine runs a full operating system on virtualized hardware, separate from the host OS.

What do containers share with the host system?

A Full operating system

B Hardware only

C Nothing

D Operating system kernel

Containers share the host operating system kernel but isolate the application environment.

Which is a key advantage of containers over virtual machines?

A They run slower

B They are more lightweight and start faster

C They require more disk space

D They need separate hardware

Containers are lightweight and start quickly because they share the host OS kernel.

Virtualization allows one physical computer to run:

A Multiple virtual machines with different OSes

B Only one operating system

C Only containers

D No operating system

Virtualization lets one physical computer run multiple virtual machines, each with its own OS.

Which analogy best explains containers?

A Separate houses on different land

B Apartments in a building

C Rooms in a house sharing utilities

D Different buildings on the same street

Containers are like rooms in a house sharing utilities (OS kernel), but isolated for privacy.

Explain virtualization and how it helps use computer resources efficiently.

Think about how one computer can act like many.

Describe containers and how they differ from virtual machines using a simple analogy.

Consider comparing containers to rooms and virtual machines to apartments.

Practice

1. What is the main difference between virtualization and containers?

easy

A. Virtualization creates full separate computers; containers share the main OS.

B. Containers create full separate computers; virtualization shares the main OS.

C. Both virtualization and containers create full separate computers.

D. Both virtualization and containers share the main OS without isolation.

Solution

1. Step 1: Understand virtualization

   Virtualization creates full separate computers inside one physical machine, each with its own OS.

2. Step 2: Understand containers

   Containers isolate applications but share the main operating system, making them lighter.

3. Final Answer:

   Virtualization creates full separate computers; containers share the main OS. -> Option A

4. Quick Check:

   Virtualization = full OS, Containers = shared OS [OK]

Hint: Virtualization = full OS; containers = shared OS [OK]

Common Mistakes:

• Confusing which one shares the OS
• Thinking containers create full OS
• Assuming both are the same

2. Which of the following is the correct way to describe a container?

easy

A. A full virtual machine with its own OS.

B. A physical server dedicated to one application.

C. A cloud service that runs only on virtual machines.

D. An isolated app environment sharing the host OS.

Solution

1. Step 1: Define container

   A container isolates an application but shares the host operating system with other containers.

2. Step 2: Eliminate incorrect options

   Options A and B describe virtual machines or physical servers, not containers. A cloud service that runs only on virtual machines. is about cloud services, not containers.

3. Final Answer:

   An isolated app environment sharing the host OS. -> Option D

4. Quick Check:

   Container = isolated app + shared OS [OK]

Hint: Containers isolate apps but share OS [OK]

Common Mistakes:

• Thinking containers have their own OS
• Confusing containers with physical servers
• Mixing cloud services with containers

3. Consider this diagram showing a computer running virtualization and containers:

Which layer is shared by all containers but not by virtual machines?

medium

A. Guest Operating System

B. Hypervisor

C. Host Operating System

D. Virtual Machine Kernel

Solution

1. Step 1: Identify container layers

   Containers share the Host Operating System kernel to run isolated apps efficiently.

2. Step 2: Identify virtual machine layers

   Virtual machines run separate Guest Operating Systems via a Hypervisor, so they do not share the Host OS kernel.

3. Final Answer:

   Host Operating System -> Option C

4. Quick Check:

   Containers share Host OS; VMs do not [OK]

Hint: Containers share Host OS; VMs have separate OS [OK]

Common Mistakes:

• Choosing Hypervisor as shared layer
• Confusing Guest OS with Host OS
• Thinking VMs share Host OS kernel

4. A developer tries to run two applications in containers but notices they interfere with each other's files. What is the most likely cause?

medium

A. Containers are not properly isolated and share file systems.

B. Virtual machines are running on the same host.

C. The host OS crashed and caused file corruption.

D. Containers always share all files by design.

Solution

1. Step 1: Understand container isolation

   Containers should isolate apps including file systems, but misconfiguration can cause shared file access.

2. Step 2: Analyze other options

   Virtual machines do not cause container file interference. Host OS crash is unrelated. Containers do not always share files by design.

3. Final Answer:

   Containers are not properly isolated and share file systems. -> Option A

4. Quick Check:

   Improper isolation causes file sharing [OK]

Hint: Check container isolation settings for file sharing issues [OK]

Common Mistakes:

• Blaming virtual machines for container issues
• Assuming containers always share files
• Ignoring misconfiguration possibilities

5. A company wants to run 10 different apps on one physical server. They want fast startup, low resource use, and strong isolation. Which setup is best?

hard

A. Run 10 virtual machines, each with its own OS.

B. Run 10 containers sharing the host OS.

C. Run 5 virtual machines and 5 containers mixed.

D. Run all apps directly on the host OS without isolation.

Solution

1. Step 1: Analyze requirements

   Fast startup and low resource use favor containers because they share the host OS and are lightweight.

2. Step 2: Consider isolation

   Containers provide good isolation for apps, though less than full VMs, but balance speed and resource use well.

3. Step 3: Compare options

   Running 10 VMs uses more resources and slower startup. Mixed setups add complexity. Running apps without isolation risks conflicts.

4. Final Answer:

   Run 10 containers sharing the host OS. -> Option B

5. Quick Check:

   Containers = fast, low resource, good isolation [OK]

Hint: Containers balance speed, resource use, and isolation best [OK]

Common Mistakes:

• Choosing full VMs for speed and resource use
• Ignoring isolation needs
• Running apps without any isolation