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Difference between docker stop and docker kill commands

I. Overview

Docker is an operating system-level software framework for creating, managing, and running containers on servers and the cloud. Docker supports stopping containers in two different ways.

In this tutorial, we will learn to stop and terminate containers using docker stopand commands.docker kill

We will use different docker commands to stop and delete containers.

2. Comprehension docker stopand docker killCommand

Starting and stopping a container is not the same as starting and stopping a normal process. To terminate a container, Docker provides docker stopand docker killcommands. docker killand docker stopcommands look similar, but their internal execution is different.

docker stopCommands send the SIGTERM signal, and docker killcommands send the SIGKILL signal. Execution of SIGTERM and SIGKILL. is different. Unlike SIGKILL, SIGTERM terminates the process gracefully rather than immediately. The SIGTERM signal can be handled, ignored, or blocked, but the SIGKILL signal cannot be blocked or handled. SIGTERM allows the child or parent process the opportunity to send information to other processes.

With SIGKILL, we may create zombie processes because the killed child process cannot notify its parent that it received the kill signal. It will take some time for the container to shut down completely.

3. Execution docker stopand docker killcommands

Before we go any further docker stopdocker killlet's first run a sample Postgres Docker container:

$ docker run -itd -e POSTGRES_USER=baeldung -e POSTGRES_PASSWORD=baeldung
 -p 5432:5432 -v /data:/var/lib/postgresql/data --name postgresql-baedlung postgres
 Unable to find image 'postgres:latest' locally
 latest: Pulling from library/postgres
 214ca5fb9032: Pull complete
 95df4ec75c64: Pull complete
 Digest: sha256:2c954f8c5d03da58f8b82645b783b56c1135df17e650b186b296fa1bb71f9cfd
 Status: Downloaded newer image for postgres:latest

Let's see the details of the container:

$ docker ps
 be2848539d76 postgres "docker-entrypoint.s…" 4 seconds ago Up 2 seconds>5432/tcp postgresql-baedlung

docker pscommand to list all running processes on the host.

3.1. docker stopOrder

docker stopThe command gracefully stops the container and provides a safe way out. If docker stopthe command fails to kill the process within the specified timeout, Docker implicitly issues the kill command immediately. In Docker, we can use docker stopcommands in two ways to stop a process. We can use containerIdor container name to stop the container.

Let's demonstrate stopping a container using the container name:

$ docker stop postgresql-baeldung

Let's use an example to containerIdstop the container:

$ docker stop be2848539d76

Interestingly, we can also use the containerId prefix to start or stop a container. Here, we just need to make sure that no other containers are containerIdrunning with "be" as startup:

$ docker stop be

By default, the docker stopcommand waits 10 seconds to kill the process. But we can -tconfigure the wait time with options:

$ docker stop -t 60 be2848539d76

Here, the container will wait 60 seconds before force removing the container. We can also docker container stopstop the container with the command:

$ docker container stop -t 60 be2848539d76

Both commands work exactly the same way. Docker docker container stopcommands are deprecated in newer versions of Docker.

3.2. docker killCommands

docker killThe command abruptly terminated the entrypoint process. docker killcommand will cause an unsafe exit. In some cases, docker containers run with volumes mounted with the host. This can lead to filesystem corruption if there are still pending changes in memory when the main process is stopped.

Let's see the command to kill a container:

$ docker kill be2848539d76

Similarly, to kill a container, we can also use the docker container killcommand:

$ docker container kill be2848539d76

docker container killCommands work docker killsimilarly to commands.

4. Additional commands to stop the container

docker killand docker stopcommand will stop the container. Another way to stop a container is to delete it. We can use the docker rmcommand to remove a container. This will immediately remove the container from local storage:

$ docker rm be2848539d76

When we run docker rmthe command, the container is removed from the docker ps -alist. While using docker stopcommands, we can reserve containers for reuse. Ideally, we can put the container in two states. A container can enter a stopped or paused state. If a container is stopped, all resources it allocated are freed, while a suspended container does not free memory, but CPU. In this case, the process is suspended.

Let's see the command to pause the container:

$ docker pause be2848539d76

It's worth noting that we can inspect the container details even after the container is stopped. To learn more about containers, we can use the docker inspectcommand. docker inspectThe command displays the container's exit code in the container state. When using the docker stopcommand to stop the container, the exit code is 0. Likewise, the docker killcommand displays the container status as a non-zero exit code.

5 Conclusion

In this tutorial, we discussed the difference between execute docker stopand docker killcommand. First, we discussed using different commands to stop containers. Next, we discussed the implementation of SIGTERM and SIGKILL in the docker stop and docker kill commands.

We also explored the different options for these two commands. Later, we explored docker container stop,and docker container killordered.

In short, we learned various ways to stop and kill Docker containers.


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