Answers

Here are some sample answers to the questions presented in this chapter:

1. Linux had to first introduce namespaces and cgroups to make containers possible. Containers use those two concepts extensively. Namespaces are used to encapsulate and thus protect resources defined and/or running inside a container. cgroups are used to limit the resources processes running inside a container can use, such as memory, bandwidth, or CPU.
2. The possible states of a Docker container are as follows:
   • created: A container that has been created but not started
   • restarting: A container that is in the process of being restarted
   • running: A currently running container
   • paused: A container whose processes have been paused
   • exited: A container that ran and completed
   • dead: A container that Docker Engine tried and failed to stop
3. We can use the following (or the old, shorter version, docker ps):

   $ docker container ls

This is used to list all containers that are currently running on our Docker...