Book Image

Learn Docker - Fundamentals of Docker 18.x

By : Dr. Gabriel N. Schenker
Book Image

Learn Docker - Fundamentals of Docker 18.x

By: Dr. Gabriel N. Schenker

Overview of this book

Docker containers have revolutionized the software supply chain in small and big enterprises. Never before has a new technology so rapidly penetrated the top 500 enterprises worldwide. Companies that embrace containers and containerize their traditional mission-critical applications have reported savings of at least 50% in total maintenance cost and a reduction of 90% (or more) of the time required to deploy new versions of those applications. Furthermore they are benefitting from increased security just by using containers as opposed to running applications outside containers. This book starts from scratch, introducing you to Docker fundamentals and setting up an environment to work with it. Then we delve into concepts such as Docker containers, Docker images, Docker Compose, and so on. We will also cover the concepts of deployment, orchestration, networking, and security. Furthermore, we explain Docker functionalities on public clouds such as AWS. By the end of this book, you will have hands-on experience working with Docker containers and orchestrators such as SwarmKit and Kubernetes.
Table of Contents (21 chapters)
Title Page
Packt Upsell
Contributors
Preface
Index

Listing resource consumption


Over time, a Docker host can accumulate quite a bit of resources such as images, containers, and volumes in memory and on disk. As in every good household, we should keep our environment clean and free unused resources to reclaim space. Otherwise, there will come the moment when Docker does not allow us to add any more new resources, meaning actions such as pulling an image can fail due to lack of available space on disk or in memory.

The Docker CLI provides a handy little system command that lists how much resources currently are used on our system and how much of this space can possibly be reclaimed. The command is:

$ docker system df

If you execute this command on your system, you should see an output similar to this:

TYPE          TOTAL   ACTIVE   SIZE      RECLAIMABLE
Images        21      9        1.103GB   845.3MB (76%)
Containers    14      11       9.144kB   4.4kB (48%)
Local Volumes 14      14       340.3MB   0B (0%)
Build Cache                    0B  ...