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Asked: 2024-09-25T14:38:12+05:30 In:

How can I properly terminate a Docker container that was started with the `docker run` command?

I’ve been diving into Docker lately and I ran into a bit of a snag that I could use some help with. I started a container using the `docker run` command, and now I’m trying to figure out the best way to properly terminate it. I know there’s more than one way to do it, but I’m not sure what the best practices are or what might happen if I just do it haphazardly.

So here’s the deal: I launched this container to test some simple application, and it’s running fine. But now, I want to stop it because I’ve finished my tests. I’ve read up on different commands, and I think I could just use `docker kill` or `docker stop`, but honestly, I don’t know which is the better choice. What are the differences between them?

The last thing I want is to leave some orphaned processes hanging around or, worse, mess something up in my container that I’m trying to clean up. Also, I remember seeing something about how closing the terminal session might impact the container’s operation, so I’m a little worried that I might inadvertently leave it running.

Plus, what happens if I want to restart the container later? Are there any implications based on how I terminate it? Should I be concerned about data loss, especially if I was running a database in that container?

I can definitely see the advantages of properly shutting things down to ensure everything is clean and tidy, but sometimes it feels like the Docker commands have a bit of a learning curve. Any tips, tricks, or personal anecdotes about the best way to handle container termination would really help me figure this out. What has your experience been like with this? Am I overthinking it, or are there significant differences in the ways to stop a Docker container that I should be aware of? Looking forward to hearing your thoughts!

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    2 Answers

    1. Stopping a Docker container can indeed be a bit confusing if you’re new to the platform. The primary commands to consider are `docker stop` and `docker kill`. The `docker stop` command is generally the recommended approach when you want to terminate a container gracefully. It sends a SIGTERM signal to the container’s main process, allowing it to clean up resources and perform any necessary shutdown procedures. If the process does not terminate within the allotted timeout (defaulting to 10 seconds), `docker stop` will then send a SIGKILL to forcefully stop it. On the other hand, `docker kill` immediately sends a SIGKILL signal, which does not allow the process to perform any cleanup. This may lead to residual data or orphaned processes, so it should be used cautiously, especially when dealing with applications like databases where data integrity is critical.

      When it comes to closing the terminal session, if you’ve detached from the container using `docker run -d`, it will continue running in the background, unaffected by the terminal session closing. However, if you started it without detaching (interactively), closing the terminal might stop the container unless it is explicitly run in detached mode. Regarding restarting containers, using `docker stop` ensures a clean exit, allowing you to start the same container again without issues. On the other hand, using `docker kill` may lead to a state where files aren’t saved correctly, especially for databases, resulting in potential data loss. Always ensure data persistence, especially when working with databases in containers, by mounting volumes. Being mindful of these practices will help maintain clean and efficient usage of Docker containers in your development workflow.


    2. Stopping a Docker container can be a bit tricky when you’re just getting started, but don’t worry! It’s actually pretty straightforward once you get the hang of it.

      You mentioned the commands docker kill and docker stop. Here’s the deal:

      • docker stop: This is the gentler option. It sends a SIGTERM signal to the main process in the container and gives it some time to shut down cleanly (default is 10 seconds). If it doesn’t stop in that time, it’ll then send a SIGKILL to force it to quit. This is usually the way to go because it lets your application close files, finish requests, and generally clean up after itself.
      • docker kill: This one just sends a SIGKILL immediately, which is like saying “just stop right now!” It doesn’t give your application a chance to clean up, so it could lead to data loss, especially if you’re running something like a database. Use this only if you really need to force the container to stop.

      If you just close the terminal, it depends on how you started your container. If you used docker run without the -d flag (which stands for “detached”), then yes, the container might stop when you close the terminal. But if you ran it with -d, it’ll keep running in the background.

      Now, about restarting the container later: If you use docker stop, you can easily restart it with docker start [container_name]. If you kill it without shutting it down properly, you might run into weird issues, especially if you were using persistent storage. Data could be corrupted, or it could leave behind orphaned processes.

      Also, if you had anything that was creating or modifying data inside the container (like a database), definitely check to see how it handles shutdowns. You don’t want to lose anything important!

      So in short, go with docker stop most of the time. It’s the better practice for making sure everything stays tidy. And don’t stress too much; everyone has to learn this stuff and it gets easier with time!


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