2 Understanding containers

Kubernetes primarily manages applications that run in containers - so before you start exploring Kubernetes, you need to have a good understanding of what a container is. This chapter explains the basics of Linux containers that a typical Kubernetes user needs to know.

2.1       Introducing containers

In Chapter 1 you learned how different microservices running in the same operating system may require different, potentially conflicting versions of dynamically linked libraries or have different environment requirements.

When a system consists of a small number of applications, it’s okay to assign a dedicated virtual machine to each application and run each in its own operating system. But as the microservices become smaller and their numbers start to grow, you may not be able to afford to give each one its own VM if you want to keep your hardware costs low and not waste resources.

2.1.1   Comparing containers to virtual machines

2.1.2   Introducing the Docker container platform

2.1.3   Introducing Docker alternatives and the Open Container Initiative

2.2       Exploring containers hands-on

2.2.1   Installing Docker and running a Hello World container

2.2.2   Creating a containerized Node.js web application

2.2.3   Creating a Dockerfile to build the container image

2.2.4   Building the container image

2.2.5   Running the container image

2.2.6   Distributing container images

2.2.7   Stopping and deleting containers

2.3       Understanding what makes containers possible

2.3.1   Using Namespaces to customize the environment of a process

2.3.2   Exploring the environment of a running container

2.3.3   Limiting a process’ resource usage with Linux Control Groups

2.3.4   Strengthening isolation between containers

2.4       Summary