Images are fundamental to creating containers, and this topic represents around 20% of the DCA exam questions. We covered Docker images in depth in Chapter 2, Building Docker Images, but we also talked about them in Chapter 3, Running Docker Containers, Chapter 6, Introduction to Docker Content Trust, and Chapter 13, Implementing an Enterprise-Grade Registry with DTR. In this chapter, we will quickly review all of the concepts seen in those chapters as a summary.
Let's review the most important concepts, features, and actions associated with Docker images before getting into the required knowledge section:
- Images are based on copy-on-write filesystem strategies. They are based on different overlapping layers, applied using different union filesystems and storage drivers. Currently, the most used filesystem driver for containers is overlay2. Docker Engine chooses the most adequate graph driver for our system, although we can change it.
- Containers...