Important Docker commands for Beginners

In our earlier tutorial, we learned to install Docker on RHEL\ CentOS 7 & also created a docker container. In this tutorial, we will learn some important Docker commands to manipulate a docker container.

(Recommended read: Step by step guide to create Docker Image )

(Also read: Create & manage docker hosts with Docker Machine on VirtualBox)

Syntax for using Docker command

$ docker [option] [command] [arguments]

To view the list of all available commands that can be used with docker, run

& we will get the following list of commands as the output,

attach — Attach to a running container

build — Build an image from a Dockerfile

commit — Create a new image from a container’s changes

cp — Copy files/folders between a container and the local filesystem

create — Create a new container diff Inspect changes on a container’s filesystem

events — Get real time events from the server

exec — Run a command in a running container

export — Export a container’s filesystem as a tar archive

history — Show the history of an image

images — List images import Import the contents from a tarball to create a filesystem

image info — Display system-wide information

inspect — Return low-level information on a container or image

kill — Kill a running container load Load an image from a tar archive or STDIN

login — Log in to a Docker registry logout Log out from a Docker registry

logs — Fetch the logs of a container network Manage Docker networks

pause — Pause all processes within a container

port — List port mappings or a specific mapping for the CONTAINER

ps — List containers pull Pull an image or a repository from a registry

push — Push an image or a repository to a registry

rename — Rename a container

restart — Restart a container

rm — Remove one or more containers

rmi — Remove one or more images

run — Run a command in a new container

save — Save one or more images to a tar archive

search — Search the Docker Hub for images

start — Start one or more stopped containers

stats — Display a live stream of container(s) resource usage statistics

stop — Stop a running container

tag — Tag an image into a repository

top — Display the running processes of a container

unpause — Unpause all processes within a container

update — Update configuration of one or more containers

version — Show the Docker version information

volume — Manage Docker volumes wait Block until a container stops, then print its exit code

To further view the options available with a command, run

$ docker docker-subcommand info

& we will get a list of options that we can use with the docker-sub command.

Testing connection with Docker Hub

By default, all the images that are used are pulled from Docker Hub. We can upload or download an image for OS from Docker Hub. To make sure that we can do so, run

& the output should be,

Hello from Docker. This message shows that your installation appears to be working correctly. …

This output message shows that we can access Docker Hub & can now download docker images from Docker Hub.

Searching an Image

To search for an image for the container, run

& we should get list of available Ubuntu images. Remember if you are looking for an official image, look for [OK] under the official column.

Downloading an image

Once we have searched and found the image we are looking for, we can download it by running,

Viewing downloaded images

To view all the downloaded images, run

Running an container

To run a container using the downloaded image , we will use

Here, using ‘-it’ will open a shell that can be used to interact with the container. Once the container is up & running, we can then use it as a normal machine & execute any commands that we require for our container.

Displaying all docker containers

To view the list of all docker containers, run

The output will contain list ofcontainers with container id.

Stopping a docker container

To stop a docker container, run

$ docker stop container-id

Exit from the container

To exit from the container, type

Saving the state of the container

Once the container is running & we have changed some settings in the container, like for example installed apache server, we need to save the state of the container. Image created is saved on the local system.

To commit & save the state of the container, run

$ docker commit 85475ef774 repository/image_name

Here, commit will save the container state,

85475ef774, is the container id of the container,

repository, usually the docker hub username (or name of the repository added)

image_name, will be the new name of the image.

We can further add more information to the above command using ‘-m’ & ‘-a’. With ‘-m’, we can mention a message saying that apache server is installed & with ‘-a’ we can add author name.

For example

docker commit -m “apache server installed”-a “Dan Daniels” 85475ef774 daniels_dan/Cent_container

This completes our tutorial on important docker commands, please share your comments/queries in the comment box below.

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Originally published at linuxtechlab.com on April 16, 2018.