Hi,
The command to execute something in a container is -
docker exec <container_id/container_name> <instruction/cmd to be executed>
In your case, you are trying to send a mail I believe, so:
docker exec -d <container_name> sendmail -f user@yahoo.com
This should run the command in a detached state/ run the process in the background.
In case you want your stdin to be open, replace -d with -i.
sendmail is an utility I believe, incase it is not running, run the command from inside the container and if needed install the sendmail util:
docker exec -i -t <container_name> /bin/bash (or /bin/sh)
This tells docker to run it in an interactive mode, gives you back a tty/terminal and runs the /bin/bash command to provides you a bash terminal basically.
Run the cmd from the terminal and check :)
FAQs
Running commands in interactive mode allows us to open a shell inside the container, enabling us to execute multiple commands and interact with the container's environment. To run a command in interactive mode, use the following syntax: docker exec -it CONTAINER COMMAND [ARG...]
Can you run docker commands inside a docker container? ›
This means that containers can run system-level software such as Docker, Kubernetes, systemd, etc., without requiring privileged mode or special configuration. Once inside the container, you can run Docker commands on its shell.
How to exec command in docker container? ›
Docker Exec: How to Enter Into a Docker Container's Shell?
- Docker Exec Syntax.
- Accessing a Container's Shell Using Docker Exec. Step 1: Run a container. Step 2: Check the container status. Step 3: Access the container's shell. Step 4: Run commands using the shell. Step 5: Exit the container's shell. Conclusion. Hemanta Sundaray.
Docker containers are designed to be accessed as root users to execute commands that non-root users can't execute. We can run a command in a running container using the docker exec. We'll use the -i and -t option of the docker exec command to get the interactive shell with TTY terminal access.
How to run bash command in docker container? ›
Like before, the docker run bash command starts a new Docker container from the Debian image and runs a Bash shell inside it. The output root@container_id:/# is the command prompt of the new Bash shell, indicating that you're now inside the Docker container and ready to run commands.
How to run commands inside a container? ›
The docker exec command runs a new command in a running container. The command you specify with docker exec only runs while the container's primary process ( PID 1 ) is running, and it isn't restarted if the container is restarted. The command runs in the default working directory of the container.
How to run shell script on docker container from host? ›
When might you want to run a shell script in your Dockerfile?
- COPYing the shell script into the Docker image through the Dockerfile, then either:
- RUNning the script or.
- listing the script as the default command to run in the container with CMD.
Essentially, the exec command allows you to run commands within an already deployed container. The exec command allows you to do this in two different ways…from inside or outside the container. I'm going to show you how to do both. In the end, you'll be better prepared to interact with your running Docker containers.
What is the difference between docker exec and Docker compose exec? ›
So, docker-compose exec is basically identical to docker exec . It is a debugging tool that can run an additional command inside a running container. It runs in the same environment as the container's main process, with the same container-private filesystem.
What is the difference between run and exec in Docker compose? ›
The run command will spin up a new container for you to use. The exec command will allow you to use a container that is already running.
By default, commands executed with docker exec run as the root user inside the container. However, we can specify a different user to run the command. To run a command as a different user, use the following syntax: docker exec -u USERNAME CONTAINER COMMAND [ARG...]
Why not run as root in docker? ›
Running your containers as non-root prevents malicious code from gaining permissions in the container host and means that not just anyone who has pulled your container from the Docker Hub can gain access to everything on your server, for example.
How do I run an exec from the command line? ›
Type start [filename.exe] into Command Prompt.
Replace [filename.exe] with your program's name. This should exactly match your exe program's file name in the folder. For example, if you're running Mozilla Firefox, the program file should be named firefox.exe by default.
Can I use localhost inside a docker container? ›
internal:host-gateway directs docker-compose to add an entry to the container's /etc/hosts file that maps the hostname host. docker. internal to the host machine's IP address. As a result, the host machine's localhost can be accessed from within the Docker container by using the hostname host.
How to run docker container with multiple commands? ›
To execute multiple commands in the docker run command, we can use the && operator to chain the commands together. The && operator executes the first command, and if it's successful, it executes the second command.
Where we can run docker commands? ›
By default, the Docker command line stores its configuration files in a directory called .docker within your $HOME directory. Docker manages most of the files in the configuration directory and you shouldn't modify them.
Can docker containers talk to each other? ›
With Docker, we commonly build containers that can communicate over isolated networks. However, we might have multiple containers communicating on the same host. This happens, for example, during integration tests. Docker provides a network definition with different options.
