Docker Stop Command |A Complete Tutorial:Defnition,Syntax,Examples

In the field of Docker container management, the docker stop command serves as a critical tool for mainly shut-down containers. This article talks about the working of the docker stop command, explaining its purpose, usage, and importance of proper container termination.

The primary function of `docker stop` is to stop the execution of a running container. When we run this command shut down, it sends a default SIGTERM signal to the main process within the container, allowing it to perform cleanup operations before terminating the container.

The main process behind the docker container stop goes as, Firstly it sends SIGTERM signal inside the docker container, and after certain short intervals known as grace period, SIGKILL signal command shut will be sent. The first signal SIGTERM acts as warming to the grace period (default 10 secondsthe) it will forcibly seconds shut down, the container.

docker stop [OPTIONS] [CONTAINER…]

• `OPTIONS` : provides additional settings for the stop operation of the Docker container.
• `CONTAINER`: The ID or name of the container is to be specified to stop the specific container.

Assume, A container with name my_container running in your local docker system. You want to terminate that that container. The following command helps in terminating that container:

docker stop my_container

Before trying the docker commands ensure that the docker software is set up and the service is active. Check the status of the docker service with the command `systemctl status docker`. If the status is active then the docker service is ready to use and then you are good to perform the container operations and management. To check the status of the docker service use the following command:

 systemctl status docker

• You can see in the below figure how to run and check the above command for checking the status of docker.

When you use a `docker stop` as a docker command, Docker initiates a immediate shutdown process. The container receives the SIGTERM signal, allowing its main process to perform the cleanup tasks, such as saving state or closing connections. If the container doesn’t respond to the SIGTERM signal within a specified timeout (default is 10 seconds), Docker sends a SIGKILL signal, forcefully terminating the container.

docker stop <container_name or Id>

1. `-t` or `–time`: It sets a custom timeout period for the docker container to respond to the SIGTERM signal before forcefully stopping it. In this example the docker container with my_containername wait for the 30seconds after sending the SIGTERM signal then it will go for forcefully termination if it is not responded in that 30seconds.

 docker stop -t 30 my_container

2. `–time=0`: In this, the docker skip the graceful shutdown period and makes immediately send a SIGKILL signal to kill the docker container.

docker stop --time=0 my_container

For starting a docker container we use docker start command, but in general we go with docker run command which helps in both starting a container and running a container. Here We are the providing an example of start and running a docker container with ubuntu docker image. The command looks as follows:

docker run -it --name mycontainer1 ubuntu:latest /bin/bash

• The following screenshot illustrates clearly of creating and running the docker container with interactive mode.

• To know more about Docker Run Command, Refer this – Docker Run Command

In this below figure you can see the containers that are running through `docker ps` command , are get stopped once we run the command of `docker stop container_name/container_id` . In the status section of the docker ps , we can see that earlier the container is running from 16minutes and once we run the docker stop command the containers get termination its been 8 seconds from that moment. To know more about docker commands refer to the Docker-Cheat Sheet.

Follow the below steps to stop one Docker running container at a time.

Step 1: Start The Docker Service

• Open your command line containing the Docker software and start The Docker Service with following command:

systemctl enable docker --now

Step 2: Run A Docker Container

• Start The Container using docker run, for example take this as a command:

docker run -dit --name mycontainer centos:latest

Step 3: List The Running Containers

• Run the following command to view the running containers:

docker ps

• To know and view all the containers either they are running or get terminated specify the above command with option -a , the command looks as given below:

docker ps -a

Step 4: Stop The Docker Container

• If multiple containers are running then the specific container name or ID that you are looking to stop. In this case I want to stop the container with name mycontainer.

docker stop mycontainer

• In this, the docker container with name my_container is get stopped from the execution, by sending the SIGTERM signal to backend through the option stop and finally the my_container leads to the graceful termination. This below shows you that clearly.

Step 5: Stop The Docker Container With Time Period ( Optional )

• You can also stop a running docker container with a grace period of 30 seconds and exits.

docker stop --time=30 myc1

In this we specified the docker container ID instead of docker container name for stoping from the execution and making the container with id ‘d3ca5e7b6f8b‘ for graceful termination. while specifying the container id we have to make ensure it is unique with id from other , we don’t need to specify all the characters of the container id.

docker stop d3ca5e7b6f8

When you execute a docker stop command along with the container name or id, the docker on behind sends two single signals to the container before the termination. The first signal known as SIGTERM signal warns the container for possible termination after the default grace time of 10seconds it sends another signal known as SIGKILL signal that terminates the running container. The Flow of docker stop explain in steps as follows:

Step 1: Initiating Stop process by running command as follows:

docker stop <container_name or container_id>

Step 2: Docker sends SIGTERM signal to container.

Step 3: Graceful Shutdown (If possible): When the container receives the SIGTERM signal the main process of container starts cleaning of necessary tasks and closing connections.

Step 4: Timeout Period, By default timeout period 10seconds are provided, or else you can customize and set our time for the main process to clean the tasks.

Step 5: Send SIGKILL Signal (If Necessary), If the container is not able to respond with termination of the container within the specified time, docker sends SIGKILL signal to the container immediately.

Docker kill command sends only one signal known as SIGKILL signal that terminate the running container, it doesn’t provide any grace time for the container’s main process to clean the tasks, close the connections. That the reason, this docker kill command takes lesser time compared to docker stop command. It is only recommended to use docker kill in necessary cases. It preferred to not to use it in generally.

The force stopping of a docker container is the known killing a container, The above section explained how the docker kill command works. It directly sends a SIGKILL signal to the Container. The following steps helps in killing the docker container.

Step 1: List the docker containers and chose the running container you want to force stop. The following command help in listing the running containers.

docker ps

Step 2: Now run the following command to force stop the container that you want to kill. Here I want to force stop the myc1 named running container.

docker kill myc1

Step 3: Verify the step2 by listing the containers with the following command:

docker ps

The following steps guide you in stopping all the running docker containers at once:

Step 1: Start The Stopped/Paused Containers

• Firstly ensure to have many running containers to understand this concept effectively.
• Begin all the paused containers to running state and try on creating new containers if interested. Use the following command to start all the paused containers at once.

docker start $(docker ps -a -q)

Step 2: Listing All The Docker Containers

• Check all the containers’ status once by running the following command:

docker ps -a

Step 3: Stop All The Docker Containers

• Now Stop the all the running containers with the following command;

docker stop $(docker ps -aq)

( or )

• You can also stop the execution simultaneously through one command by specifying their names or IDs one by one with space separation.

docker stop container1 container2

Step 4: Verify Listing The Running Containers

• As a verification, you can use the following command “docker ps”. It displays empty that means all the running containers are successfully stopped.

In Docker, Containers can be deleted using rm option similar to for stopping we use stop command. The following are the steps guiding how to delete a docker container.

Step 1: Firstly stop the container that you intended to delete using the steps discussed above section. Its is necessarily recommended to stop the running container before deleting them.

• If you tried deleting a running container without stopping it first, It raises the error while deleting it. The command to stop the container is as follows:

docker stop myc1

• Here We are stopping the container named with mycontainer1.

Step 2: Remove A Container By Name

• Now Use the following command to delete that stop container named mycontainer1:

docker rm myc1

• In this screenshot you can see that after execution of above command, it prints the deleted container name.

Step 3: Listing All The Docker Containers

• Verify the containers by listing all to see whether that container is deleted or not. Use the following command to verify:

docker ps -a

• This below screenshots shown after deletion of the container “myc1″ it is removed from the list of containers successfully.

The following steps guide you how to delete all the docker containers:

Note: Ensure to have many containers available in running state to understand this concept clearly.

Step 1: Stop The all the running docker containers with this command:

docker stop `docker ps -q`

(or)

docker stop $(docker ps -aq)

Step 2: Use the following command to delete all the containers:

docker rm `docker ps -aq`

(or)

docker rm $(docker ps -aq)

• The following screenshot illustrates clearly about the removing all the containers and printing removed container ids.

Step 3: Verify whether all containers are removed successfully or not with the following command:

docker ps -aq

• This below makes you clear that all the containers are successfully deleted at once. There are no containers available to list out.

Docker container can be listed using docker ps command. The following command list all the docker containers with running state.

docker ps 

• This below screenshot makes you understand that all the running containers are listed and can see when do they have started.

The following command is used to list all the containers either it is running or in stopped state.

docker ps -a

• The below screenshot makes clear understanding for you with seeing the outputs of both commands. That `docker ps` list out only the running containers whereas `docker ps -a list ` out all the containers.

In Docker Compose, you can stop and remove the containers that are associated with your Docker compose project file on using the docker-compose down command. Lets following the implementation stepswise.

Step 1: Create A Docker Compose Yaml File

• Firstly Created a docker-compose.yaml file with the following code.

version: '3.8'

services:
  centos1:
    container_name: mycontainer1
    image: centos:latest

  centos2:
    container_name: mycontainer2
    image: centos:latest

Step 2: Start The Docker Compose Containers

• Now, start the containers specified docker-compose yaml file with the following command:

docker-compose up

Step 3: Stop And Remove The Docker Compose Containers

• Finally Stop the docker containers that are associated with docker compose with the following command:

docker-compose down

Both the commands docker container stop and docker container kill are used for terminating the containers only. But docker container stop will terminated the contianer by genrating 2 signals, firstly it sends warning singal regarding terminal, giving time (grace period) for the container to clear the resources properly and then after grace time it is terminated by docker stop forcely.

Whereas Docker container kill sends only one signal (SIGKILL) it directly shutdown the container, without giving any time for the container to clear the resources properly. That’s the reason docker kill command shutdowns the container very fast compared to docker stop. But docker kill command in only recommand to use, when the docker stop taking more time to terminated it, and it is less sensitive container application.

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In conclusion, the `docker stop` command plays a crucial role in the controlling the termination of Docker containers. It allows containers to handle shutdown signals and ensures that applications have an opportunity to clean up resources before coming to a halt. Whether you’re managing a single container or orchestrating complex applications, understanding and utilizing `docker stop` is essential for maintaining a well-organized and efficient Docker environment.

How To Stop Multiple Docker Containers Simultaneously ?

By specifying their container_names or ids we can stop all simultaneously.

docker stop container1 container2

What Is The Forceful Way Of Stopping A Container If It Doesn’t Respond To SIGTERM ?

By using -f option such as `docker stop -f <container_id>` will forcefully stop a container by sending a SIGKILL immediately.

What Happens If I Trying To Stop A Container Already Stopped Container ?

It doesn’t has no effect on it and come up with returning an error that it is already stopped.

What Is The Way To Stop All Running Containers At Once ?

`docker stop $(docker ps -q)` by running this we can stop all the running containers .Here $(docker ps -q) provides all the running containers id through using this docker stop command stop all the listed containers.

How To Set A Timeout For Stopping The Container With `docker stop` Command ?

By using option ( -t ) with docker stop command such as `docker stop -t <timeout_seconds> <container_id>` we can set a timeout for stopping the container.

What is the Difference Between `docker stop` and `docker kill` Commands ?

`docker stop` will send a SIGTERM signal for a normal shutdown, while `docker kill` sends a SIGKILL signal for immediate termination.