Docker Run Command with Examples
6 min read
Docker is a platform that allows you to develop, test, and deploy applications as portable, self-sufficient containers that run virtually anywhere.
docker run command creates a container from a given image and starts the container using a given command. It is one of the first commands you should become familiar with when starting to work with Docker.
In this article, we’ll use the official Nginx image to show various ways to run a Docker container.
Docker Run Command
docker run command takes the following form:
docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
The name of the image from which the container should be created is the only required argument for the
docker run command. If the image is not present on the local system, it is pulled from the registry.
If no command is specified, the command specified in the Dockerfile’s
ENTRYPOINT instructions is executed when running the container.
Starting from version 1.13, the Docker CLI has been restructured, and all commands have been grouped under the object they interacting with.
run command interacts with containers, now it is a subcommand of
docker container. The syntax of the new command is as follows:
docker container run [OPTIONS] IMAGE [COMMAND] [ARG...]
The old, pre 1.13 syntax is still supported. Under the hood,
docker run command is an alias to
docker container run. Users are encouraged to use the new command syntax.
A list of all
docker container run options can be found on the Docker documentation page.
Run the Container in the Foreground
By default, when no option is provided to the
docker run command, the root process is started in the foreground. This means that the standard input, output, and error from the root process are attached to the terminal session.
docker container run nginx
The output of the nginx process will be displayed on your terminal. Since, there are no connections to the webserver, the terminal is empty.
To stop the container, terminate the running Nginx process by pressing
Run the Container in Detached Mode
To keep the container running when you exit the terminal session, start it in a detached mode. This is similar to running a Linux process in the background.
-d option to start a detached container:
docker container run -d nginx
The detached container will stop when the root process is terminated.
You can list the running containers using the
docker container ls command.
To attach your terminal to the detached container root process, use the
docker container attach command.
Remove the Container After Exit
By default, when the container exits, its file system persists on the host system.
--rm options tells
docker run command to remove the container when it exits automatically:
docker container run --rm nginx
The Nginx image may not be the best example to clean up the container’s file system after the container exits. This option is usually used on foreground containers that perform short-term tasks such as tests or database backups.
Set the Container Name
In Docker, each container is identified by its
UUID and name. By default, if not explicitly set, the container’s name is automatically generated by the Docker daemon.
--name option to assign a custom name to the container:
docker container run -d --name my_nginx nginx
The container name must be unique. If you try to start another container with the same name, you’ll get an error similar to this:
docker: Error response from daemon: Conflict. The container name "/my_nginx" is already in use by container "9...c". You have to remove (or rename) that container to be able to reuse that name.
docker container ls -a to list all containers, and see their names:
docker container ls
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 9d695c1f5ef4 nginx "nginx -g 'daemon of…" 36 seconds ago Up 35 seconds 80/tcp my_nginx
The meaningful names are useful to reference the container within a Docker network or when running docker CLI commands.
Publishing Container Ports
By default, if no ports are published, the process running in the container is accessible only from inside the container.
Publishing ports means mapping container ports to the host machine ports so that the ports are available to services outside of Docker.
To publish a port use the
-p options as follows:
- If no
host_ipis specified, it defaults to
- If no
protocolis specified, it defaults to TCP.
- To publish multiple ports, use multiple
To map the TCP port 80 (nginx) in the container to port 8080 on the host localhost interface, you would run:
docker container run --name web_server -d -p 8080:80 nginx
You can verify that the port is published by opening
http://localhost:8080 in your browser or running the following
curl command on the Docker host:
curl -I http://localhost:8080
The output will look something like this:
HTTP/1.1 200 OK Server: nginx/1.17.6 Date: Tue, 26 Nov 2019 22:55:59 GMT Content-Type: text/html Content-Length: 612 Last-Modified: Tue, 19 Nov 2019 12:50:08 GMT Connection: keep-alive ETag: "5dd3e500-264" Accept-Ranges: bytes
Sharing Data (Mounting Volumes)
When a container is stopped, all data generated by the container is removed. Docker Volumes are the preferred way to make the data persist and share it across multiple containers.
To create and manage volumes, use the
-p options as follows:
host_srccan be an absolute path to a file or directory on the host or a named volume.
container_destis an absolute path to a file or directory on the container.
- Options can be
ro(read-only). If no option is specified, it defaults to
To explain how this works, let’s create a directory on the host and put an
index.html file in it:
echo "Testing Docker Volumes" > public_html/index.html
Next, mount the
public_html directory into
/usr/share/nginx/html in the container:
docker run --name web_server -d -p 8080:80 -v $(pwd)/public_html:/usr/share/nginx/html nginx
Instead of specifying the absolute path to the
public_html directory, we’re using the
$(pwd) command, which prints the current working directory.
Now, if you type
http://localhost:8080 in your browser, you should see the contents of the
index.html file. You can also use
Testing Docker Volumes
Run the Container Interactively
When dealing with the interactive processes like
bash, use the
-t options to start the container.
-it options tells Docker to keep the standard input attached to the terminal and allocate a pseudo-tty:
docker container run -it nginx /bin/bash
The container’s Bash shell will be attached to the terminal, and the command prompt will change:
Now, you can interact with the container’s shell and run any command inside of it.
In this example, we provided a command (
/bin/bash) as an argument to the
docker run command that was executed instead of the one specified in the Dockerfile.
Docker is the standard for packaging and deploying applications and an essential component of CI/CD, automation, and DevOps.
docker container run command is used to create and run Docker containers.
If you have any questions, please leave a comment below.