Docker ps -a
This command is used to know the details of all the running, stopped, or exited containers.

Docker version
We usually start by finding the installed version of docker that we are working on.

Docker pull
As the name suggests, this command pulls a specific image from the Docker Hub. All you have to do is use the command ‘docker pull’ along with the name of the image. Here is an example of pulling an image without using the tag.

Docker run
This command is used to create a container from an image.

Docker stop
The ‘docker stop’ command stops a container using the container name or its id.

Docker restart
This command is used to restart the stopped container. It is recommended to use this after rebooting the system.

Docker kill
This command is used to stop the container immediately by killing its execution. While the ‘docker stop’ command helps shut down the container in its own time, the ‘docker kill’ command stops it at once.

Docker login
This command helps you to log into your docker hub. As you try to log in, you will be asked to give your docker hub credentials.

Docker network
The ‘docker network’ command is used to know the details of the list of networks in the cluster.

If you have specified an argument along with the Docker run command, the default one specified using the CMD instruction will be ignored. Also, if you have specified multiple CMD instructions inside a single dockerfile, the one specified at the last will only be executed.

The CMD instruction has three forms –

CMD [“only_executable”,”parameter_1″,”parameter_1″] (executable form)
CMD [“parameter_1″,”parameter_2”] (used to provide default parameters to the ENTRYPOINT instruction)
CMD command param1 param2 (It is the shell form)
Example –
$ CMD echo “Command in Shell Form”
$ CMD [“/bin/bash”, “-c”, “echo Command in Exec Form”]

ENTRYPOINT Instruction
The ENTRYPOINT instruction looks almost similar to the CMD instruction. However, the main highlighting difference between them is that it will not ignore any of the parameters that you have specified in the Docker run command (CLI parameters).

When we have specified the ENTRYPOINT instruction in the executable form, it allows us to set or define some additional arguments/parameters using the CMD instruction in Dockerfile. If we have used it in the shell form, it will ignore any of the CMD parameters or even any CLI arguments.

The forms of the ENTRYPOINT Instruction are –

ENTRYPOINT [“only_executable”, “parameter_1”, “parameter_2”] (executable form)
ENTRYPOINT command parameter_1 parameter_2 (Shell form)
Example –
$ ENTRYPOINT echo “Welcome to Devops”
$ ENTRYPOINT [“/bin/bash”, “-c”, “echo Welcome to Devops”]

RUN: It is to build the container

MAINTAINER: Creates the images.

ENV: Environment for image.

COPY: Copies the file to images.

docker attach nodeapi

once attached, you can do all the cli commands like you can check the node version, run the bundle file, exit etc..

But the problem here once you exit out of this, your container is no logger in the up status. your container is also in exit status.

Docker exec
The docker exec command runs a new command in a running container. execute the below command after restarting container nodeapi in the above command.

// start the container
docker start nodeapi
// execute the exec command
docker exec -it nodeapi bash

you can exit now and if you list the containers now we can see container is still running.

docker stop issues a SIGTERM signal to the main process inside the container

docker kill (by default) issues a SIGKILL signal.

With docker kill, you may specify to send a different signal (to the main process inside the container) than the default SIGKILL signal, using the –signal flag. Same thing is not possible with the docker stop command.

With docker stop, the container(s) must comply to the shutdown request within a (configurable) grace period (which defaults to 10 seconds), after which it forcibly tries to kill the container. docker kill does not have any such timeout period.

It will suspends all processes in the specified containers. It means that the processes in the container stop running, and they are be able to resumed later.

docker pause [container id or name]

Docker Unpause:

It will resumes all the processes in the specified container. It means recovery container all processes.

docker unpause [container id or name]

Docker Image: Docker images are used to build containers and hold the entire metadata that elaborates the capabilities of the container. These images are read-only binary templates in YAML. Every image comes with numerous layers, and every layer depends on the layer below it. The first layer is called the base layer, which contains the base operating system and image. The layer with dependencies will come above this base layer. These layers will have all the necessary instructions in read-only, which will be the Dockerfile.

Docker Daemon: Docker Daemon is among the most essential components of Docker as it is directly responsible for fulfilling the actions related to containers. It mainly runs as a background process that manages parts like Docker networks, storage volumes, containers, and images. Whenever a container start up command is given through docker run, the client translates that command into an HTTP API call and returns it to the daemon. Afterwards, the daemon analyses the requests and communicates with the operating system. The Docker daemon will only respond to the Docker API requests to perform the tasks.

Docker Registry: Docker images require a location where they can be stored and the Docker registry is that location. Docker Hub is the default storage location of images that stores the public registry. However, registries can either be private or public. Every time a Docker pull request is made, the image is pulled from the desired Docker registry where it was the same.

Docker Container: A Docker container is the instance of an image that can be created, started, moved, or deleted through a Docker API. Containers are a lightweight and independent method of running applications. They can be connected to one or more networks and create a new image depending on the current state. Being a volatile Docker component, any application or data located within the container will be scrapped the moment the container is deleted or removed.