lifecycle of a Docker Container
The lifecycle of a Docker container refers to the sequence of states that a container goes through from its creation to its deletion. Understanding this lifecycle is crucial for effectively managing containers in a Dockerized environment.

Table of Contents
The Docker container lifecycle can be broken down into the following stages:
1. Create
A Docker container is created from a Docker image. This stage sets up the container with the specified configuration, but it doesn’t start the container.
2. Start
Once the container is created, it can be started using the `docker start` command. Starting a container runs the application defined in the Dockerfile or through the command line.
3. Running
The container is actively running and executing the specified command or application.
4. Pause
In this state, the container’s processes are paused, but the container itself remains running. This can be useful for temporarily suspending resource usage.
5. Unpause
The container resumes its processes after being paused lifecycle of a Docker.
6. Stop
When a container is stopped, its running processes are terminated, but the container remains on the host system.
7. Kill
This forcefully stops the container, similar to the stop command, but does so immediately without gracefully terminating the processes.
8. Restart
This stops and then starts the container again. It’s often used to recover from failures.
9. Remove
The container is deleted from the host system using the `docker rm` command. This stage clears up resources, and the container cannot be started again unless it’s recreated.
10. Die
A container enters the “dead” state if it has stopped or crashed. The container still exists on the host, but it’s not running.
Java Example Explanation of the Example
While the lifecycle management of Docker containers is more about command-line interaction, a Java application can interact with Docker using the Docker Java client library. Here’s how to manage a Docker container lifecycle programmatically in Java.
Step-by-Step Example:
1. Add Docker Java Library to Your Project:
To interact with Docker from Java, add the Docker Java client library dependency to your `pom.xml` if you're using Maven:
```xml
<dependency>
<groupId>com.github.docker-java</groupId>
<artifactId>docker-java</artifactId>
<version>3.2.8</version>
</dependency>
```
2. Create a Docker Client:
Create a Docker client instance to connect to the Docker daemon.
```java
DockerClient dockerClient = DockerClientBuilder.getInstance().build();
```
3. Create a Docker Container:
Use the Docker client to create a container from an image.
```java
CreateContainerResponse container = dockerClient.createContainerCmd("alpine")
.withCmd("echo", "Hello, Docker!")
.exec();
```
4. Start the Container:
Start the container using its ID.
```java
dockerClient.startContainerCmd(container.getId()).exec();
```
5. Stop the Container:
Stop the container.
```java
dockerClient.stopContainerCmd(container.getId()).exec();
```
Finally, remove the container from the Docker host.
```java
dockerClient.removeContainerCmd(container.getId()).exec();
```
Explanation of the Example lifecycle of a Docker
- DockerClient: The
DockerClient
class is used to create, manage, and remove Docker containers programmatically. It interacts with the Docker daemon. - CreateContainerCmd: The
createContainerCmd
method is used to create a new container. The image used here is “alpine”, a minimal Docker image, and the container is set to run the commandecho "Hello, Docker!"
. - startContainerCmd: This starts the container, which begins running the specified command.
- stopContainerCmd: This stops the running container.
- removeContainerCmd: This removes the stopped container from the Docker host.
This Java example demonstrates how to interact with the lifecycle of a Docker programmatically, highlighting the key lifecycle stages like create, start, stop, and remove.