So far, we have gotten acquainted with major concepts in Docker like Docker Containers, Docker Image, Dockerfile, etc. Moreover, for the development and deployment of these applications, Docker provides a new range of terminology and a new set of commands. On the next docker blog, we'll discuss how Volumes work on Docker.Docker offers a set of "platform-as-a-service" products that help us develop and deploy applications by packaging them into containers. Once we know the basics of Containers, we can do really powerful stuff with more advanced tools like Docker Compose, Docker Swarm, Kubernetes, or OpenShift, etc.Ĭontainers are awesome, and we're just getting started!
#DOCKER REMOVE CONTAINER ONCE RUN IS DONE HOW TO#
Today we learnt about the different states a Container can be in - the Container Lifecycle, as well as how to use the docker cli to maneuver through those states. Or do you think I should have started with this instead of the simplified one? Interested to hear what you think. This should be easier to understand if you have read the preceding discussion. Here is a detailed diagram of the Container Lifecycle we just discussed including events in rectangles, courtesy of Docker Saigon. Here's an example of creating a container using the nginx:alpine Image and naming it app1.Įnter fullscreen mode Exit fullscreen modeīut it is recommended not to do this, especially if the data integrity of the container is important - like the case for databases. NOTE: On this state, the container is created but not started. Using the docker create command, a thin writeable layer is created over the specified Image and prepared to run the main process command ( CMD and/or ENTRYPOINT). Read the last blog to learn more about how Docker Images work. This is the first state of the container lifecycle which comes after acquiring or building an Image. Now let's discuss each state of the container lifecycle one by one. If interested, learn more about signals here. SIGTERM is usually preferred over SIGKILL since it provides a chance for graceful/safe termination of a process. Unlike SIGTERM, this signal cannot be caught or ignored, and the receiving process cannot perform any clean-up upon receiving this signal (excluding few exceptions). SIGKILL: this signal is sent to a process to cause it to terminate immediately.This allows the process to perform graceful termination releasing resources and saving state if appropriate. It can be caught and interpreted or ignored by the process. SIGTERM: this signal is sent to a process to request its termination.But for us, we'll just focus on the following 2: There are several signals, each having different purposes.
Simply put, signals as a standard way that an Operating System (OS) tells a child process how to behave. The text on the arrows corresponds to the docker commands which allow that state transition.Īs shown above, a container can be in the following states:īefore we dive into each state, we need to know a tiny bit about POSIX signals. Simplified container lifecycle state diagram The following diagram shows the states of a simplified Container Lifecycle, which determines how a Container behaves. If you haven't read the first two blogs on the 'Docker made easy' series, I highly recommend you do so. We'll also discuss POSIX signals briefly. end with a detailed view of the container lifecycle.clear confusions regarding the differences between.learn how to manage them using the docker cli.learn about the different states a container can be in.So, let's learn about the Container Lifecycle, once and for all! It will also be much easier for you to switch to more advanced Container management solutions like Docker Compose, Docker Swarm, Kubernetes, or OpenShift, etc. Luckily, once you understand how a Container works based on its Lifecycle state, you will be WAY more confident with Docker. How a Container behaves depends on which state it is in. Have you ever been confused about what's actually happening with your Docker Containers? Have you ever felt overwhelmed by the multitude of docker cli commands? Learn how a Container works based on its Lifecycle state and the Docker cli commands to manage them effectively
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