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 )
Important Docker Commands
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
|$ docker run hello-world
& 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
|$ docker search Ubuntu
& 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,
|$ docker pull Ubuntu
Viewing downloaded images
To view all the downloaded images, run
|$ docker images
Running an container
To run a container using the downloaded image , we will use
|$ docker run –it Ubuntu
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
|$ docker ps
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.
|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.