Answers

1. The correct answers are D and E.
2. A Docker container is to IT what a shipping container is to the transportation industry. It defines a standard on how to package goods. In this case, goods are the application(s) developers write. The suppliers (in this case, the developers) are responsible for packaging the goods into the container and making sure everything fits as expected. Once the goods are packaged into a container, it can be shipped. Since it is a standard container, the shippers can standardize their means of transportation, such as lorries, trains, or ships. The shipper does not really care what is in the container. Also, the loading and unloading process from one means of transportation to another (for example, train to ship) can be highly standardized. This massively increases the efficiency of transportation. Analogous to this is an operations engineer in IT, who can take a software container built by a developer and ship it to a production system and run it there in a highly standardized way, without worrying about what is in the container. It will just work.
3. Some of the reasons why containers are game-changers are as follows:
   • Containers are self-contained and thus if they run on one system, they run anywhere that a Docker container can run.
   • Containers run on-premises and in the cloud, as well as in hybrid environments. This is important for today’s typical enterprises since it allows a smooth transition from on-premises to the cloud.
   • Container images are built or packaged by the people who know best – the developers.
   • Container images are immutable, which is important for good release management.
   • Containers are enablers of a secure software supply chain based on encapsulation (using Linux namespaces and cgroups), secrets, content trust, and image vulnerability scanning.
4. A container runs on any system that can host containers. This is possible for the following reasons:
   • Containers are self-contained black boxes. They encapsulate not only an application but also all its dependencies, such as libraries and frameworks, configuration data, certificates, and so on.
   • Containers are based on widely accepted standards such as OCI.
5. The answer is false. Containers are useful for modern applications and to containerize traditional applications. The benefits for an enterprise when doing the latter are huge. Cost savings in the maintenance of legacy apps of 50% or more have been reported. The time between new releases of such legacy applications could be reduced by up to 90%. These numbers have been publicly reported by real enterprise customers.
6. 50% or more.
7. Containers are based on Linux namespaces (network, process, user, and so on) and cgroups. The former help isolate processes running on the same machine, while the latter are used to limit the resources a given process can access, such as memory or network bandwidth.
8. Docker Desktop is available for macOS, Windows, and Linux.