How to install and use Docker on Ubuntu 16.04
Introduction
Docker is an application that makes it easy to run application processes in a container, just like a virtual machine, but more portable, more resource-friendly, and more dependent on the host operating system.
There are two ways to install Docker on Ubuntu 16.04. One way is to install it on an existing installation of the operating system. The other involves using a tool to start the server, which automatically installs Docker on it.
In this tutorial, you will learn how to install and use it on an existing Ubuntu 16.04 installation.
Preparation
To follow this tutorial, you need to have the following conditions:
- 64 It’s an Ubuntu 16.04 server. Students who don’t have a server can buy it from here, but I personally recommend you to use the free Tencent Cloud Developer Lab for experimentation, and then learn to install it. Buy Server.
- For non-root users with sudo privileges, [Ubuntu 16.04 initial setup tutorial] (https://cloud.tencent.com/developer/article/1007167?from=10680) describes how to set it up.
**Note: ** Docker requires a 64-bit version and Ubuntu with a kernel version equal to or greater than 3.10. The default 64-bit Ubuntu 16.04 server meets these requirements.
All commands in this tutorial should be run as a non-root user. If the command requires root access, it will have sudo in front. [Ubuntu 16.04 initial installation tutorial] (https://cloud.tencent.com/developer/article/1007167?from=10680) describes how to add users and provide them with sudo access.
Step 1-Install Docker
The Docker installation package provided in the official Ubuntu 16.04 repository may not be the latest version. To get the latest and greatest version, install Docker from the official Docker repository. This section will show you how to do this.
First, add the GPG key of the official Docker repository to the system:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
Add the Docker repository to the APT source:
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
Next, update the package database with the Docker package in the newly added repo:
sudo apt-get update
Make sure you want to install from the Docker repo instead of the default Ubuntu 16.04 repo:
apt-cache policy docker-ce
You should see output similar to the following:
docker-ce:
Installed:(none)
Candidate:17.03.1~ce-0~ubuntu-xenial
Version table:17.03.1~ce-0~ubuntu-xenial 500500 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
17.03.0~ ce-0~ubuntu-xenial 500500 https://download.docker.com/linux/ubuntu xenial/stable amd64 Packages
Note that docker-ce is not installed, but the candidate for installation is from the Docker repository of Ubuntu 16.04. The docker-ce version number may be different.
Finally, install Docker:
sudo apt-get install -y docker-ce
Docker should now be installed, the daemon started, and the process startup process should be enabled. Check if it is running:
sudo systemctl status docker
The output should be similar to the following, indicating that the service is active and running:
● docker.service - Docker Application Container Engine
Loaded:loaded(/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active:active(running) since Sun 2016-05-0106:53:52 CDT;1 weeks 3 days ago
Docs: https://docs.docker.com
Main PID:749(docker)
Installing Docker now can not only provide you with Docker service (daemon), but also provide you with a docker command line utility or Docker client. We will discuss how to use the docker command later in this tutorial.
Step 2-Execute Docker commands without Sudo (optional)
By default, running the docker command requires root privileges-that is, you must add sudo before the command. It can also be run by a user in the docker group, which is automatically created during Docker installation. If you try to run the docker command without using sudo or without prefixing it in the docker group, you will get the following output:
docker: Cannot connect to the Docker daemon. Is the docker daemon running on this host?.
See 'docker run --help'.
If you want sudo to avoid typing when running the docker command, please add the user name to the docker group:
sudo usermod -aG docker ${USER}
To apply the new group membership, you can log out of the server and log in again, or you can enter the following:
su - ${USER}
You will be prompted to enter the user password to continue. After that, you can confirm that your user is now added to the docker group by typing the following:
id -nG
The output should look like this:
sammy sudo docker
If you need to add a user to the docker group that you are not logged in, please use the following method to clearly declare the user name:
sudo usermod -aG docker username
The rest of this article assumes that you are running the docker command as a user in the docker user group. If you do not choose to do this, please add the command sudo in front.
Step 3-Use Docker commands
With Docker installed and working, it's time to get familiar with the command line utilities. Use docker and pass a series of options and commands, followed by parameters. The syntax takes the following form:
docker [option][command][arguments]
To view all available subcommands, enter:
docker
Starting with Docker 1.11.1, the complete list of available subcommands includes:
attach Attach to a running container
build Build an image from a Dockerfile
commit Create a newimagefrom a container's changes
cp Copy files/folders between a container and the local filesystem
create Create a newcontainer
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 newcontainer
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 ofcontainer(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 view the switches available for a specific command, enter:
docker docker-subcommand --help
To view system-wide information about Docker, use:
docker info
Step 4-Use Docker image
The Docker container runs from the Docker image. By default, it fetches these images from Docker Hub, which is a Docker registry managed by Docker, the company behind the Docker project. Anyone can build and host their Docker images on Docker Hub, so most of the applications and Linux distributions required to run Docker containers have images hosted on Docker Hub.
To check if you can access and download images from Docker Hub, enter:
docker run hello-world
The output should include the following and should indicate that Docker is working properly:
Hello from Docker.
This message shows that your installation appears to be working correctly....
You can use the search command with the docker command to search for images available on Docker Hub. For example, to search for Ubuntu images, enter:
docker search ubuntu
The script will crawl Docker Hub and return a list of all images whose names match the search string. In this case, the output will be similar to:
NAME DESCRIPTION STARS OFFICIAL AUTOMATED
ubuntu Ubuntu is a Debian-based Linux operating s...3808[OK]
ubuntu-upstart Upstart is an event-based replacement for...61[OK]
torusware/speedus-ubuntu Always updated official Ubuntu docker imag...25[OK]
rastasheep/ubuntu-sshd Dockerized SSH service, built on top ofof...24[OK]
ubuntu-debootstrap debootstrap --variant=minbase --components...23[OK]
nickistre/ubuntu-lamp LAMP server on Ubuntu 6[OK]
nickistre/ubuntu-lamp-wordpress LAMP on Ubuntu with wp-cli installed 5[OK]
nuagebec/ubuntu Simple always updated Ubuntu docker images...4[OK]
nimmis/ubuntu This is a docker images different LTS vers...4[OK]
maxexcloo/ubuntu Docker base image built on Ubuntu with Sup...2[OK]
admiringworm/ubuntu Base ubuntu images based on the official u...1[OK]
...
In the OFFICIAL column, OK represents an image built and supported by the company behind the project. Once you have determined the image you want to use, you can use the pull subcommand to download it to your computer, as shown below:
docker pull ubuntu
After downloading the image, you can run the container using the downloaded image with the run subcommand. If the image is not downloaded when docker is executed with the run subcommand, the Docker client will first download the image and then use it to run the container:
docker run ubuntu
To view the images that have been downloaded to the computer, enter:
docker images
The output should be similar to the following:
REPOSITORY TAG IMAGE ID CREATED SIZE
ubuntu latest c5f1cf30c96b 7 days ago 120.8 MB
hello-world latest 94df4f0ce8a4 2 weeks ago 967 B
As you will see later in this tutorial, the image used to run the container can be modified and used to generate a new image, which can then be uploaded (push is the technical term) to Docker Hub or other Docker registry.
Step 5-Run the Docker container
Before you run the hello-world container to run and exit, an example of the container after the test message is illuminated. However, containers are more useful than this, they can be interactive. After all, they are similar to virtual machines, but more resource-friendly.
As an example, let's run a container using the latest image of Ubuntu. The combination of -i and -t switches gives you interactive shell access to the container:
docker run -it ubuntu
Your command prompt should change to reflect the fact that you are now working in the container, and should take the following form:
root@d9b100f2f636:/#
**Important: **Please note the container ID in the command prompt. In the example above, it is d9b100f2f636.
Now you can run any command inside the container. For example, let's update the package database inside the container. There is no need to prefix any commands with sudo, because you are operating in a container with root privileges:
apt-get update
Then install any applications in it. For example, let's install NodeJS.
apt-get install -y nodejs
Step 6-Submit the changes in the container to the Docker image
When you start the Docker image, you can create, modify and delete files just like using a virtual machine. The changes you made only apply to this container. You can start and stop it, but once you destroy it with the docker rm command, the changes will be lost forever.
This section describes how to save the state of the container as a new Docker image.
After installing nodejs in an Ubuntu container, you now have a container running an image, but the container is different from the image you used to create it.
To save the state of the container as a new image, exit it first:
exit
Then use the following command to commit the changes to the new Docker image instance. The -m switch is the submission information, which can help you and others know the changes you made, while the -a is used to specify the author. When you start an interactive session, the container ID is the container ID you mentioned earlier in this tutorial. Unless you have created other repositories on Docker Hub, the repository is usually your Docker Hub username:
docker commit -m "What did you do to the image"-a "Author Name" container-id repository/new_image_name
E.g:
docker commit -m "added node.js"-a "Sunday Ogwu-Chinuwa" d9b100f2f636 finid/ubuntu-nodejs
**Note: **When you submit the new image is saved locally, that is, on your computer. Later in this tutorial, you will learn how to push an image to a Docker registry such as Docker Hub so that you and others can evaluate and use it.
After completing the operation, immediately listing the Docker image on the computer should show the new image and the old image derived from it:
docker images
The output should be similar to:
finid/ubuntu-nodejs latest 62359544c9ba 50 seconds ago 206.6 MB
ubuntu latest c5f1cf30c96b 7 days ago 120.8 MB
hello-world latest 94df4f0ce8a4 2 weeks ago 967 B
In the above example, ubuntu-nodejs is the new image, which is derived from the existing ubuntu image of Docker Hub. The size difference reflects the changes made. In this example, the change is that NodeJS is already installed. Therefore, next time you need to run a container with Ubuntu with NodeJS pre-installed, you can use the new image. The image can also be built from a so-called Dockerfile. But this is a very complicated process that is beyond the scope of this article.
Step 7-List Docker containers
After using Docker for a while, you will have many active (running) and inactive containers on your computer. To view active, use:
docker ps
You will see output similar to the following:
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
f7c79cc556dd ubuntu "/bin/bash"3 hours ago Up 3 hours silly_spence
To see all containers-active and inactive, pass it to the -a switch:
docker ps -a
To see the latest container you created, pass it to the -l switch:
docker ps -l
Stopping a running or active container is as simple as typing:
docker stop container-id
The container-id can be found in the output of the docker ps command.
Step 8-Push the Docker image to the Docker repository
The next logical step after creating a new image from an existing image is to share it with a few of your choices, the entire area on Docker Hub, or other Docker registries you can access. To push an image to Docker Hub or any other Docker registry, you must have an account there.
This section describes how to push Docker images to Docker Hub.
To create an account with Docker Hub, register at Docker Hub. Then, in order to push your image, first log in to Docker Hub. You will be prompted for identity verification:
docker login -u docker-registry-username
If you specified the correct password, authentication should be successful. Then you can use the following methods to push your own images
docker push docker-registry-username/docker-image-name
It will take some time to complete, and when complete, the output will be similar to the following:
The push refers to a repository [docker.io/finid/ubuntu-nodejs]
e3fbbfb44187: Pushed
5 f70bf18a086: Pushed
a3b5c80a4eba: Pushed
7 f18b442972b: Pushed
3 ce512daaf78: Pushed
7 aae4540b42d: Pushed
...
After pushing the image to the registry, it should be listed on the dashboard of your account as shown in the image below.
If the push attempt results in this type of error, you may not be logged in:
The push refers to a repository [docker.io/finid/ubuntu-nodejs]
e3fbbfb44187: Preparing
5 f70bf18a086: Preparing
a3b5c80a4eba: Preparing
7 f18b442972b: Preparing
3 ce512daaf78: Preparing
7 aae4540b42d: Waiting
unauthorized: authentication required
Log in and repeat the push attempt.
in conclusion
Docker is much more than what is given in this article, but it is enough to get you started using it on Ubuntu 16.04. Like most open source projects, Docker is built from a rapidly developing code base, so visit the project blog page for the latest information.
See also Other Docker tutorials in the DO community.
To learn more about Linux open source information tutorial, please go to [Tencent Cloud + Community] (https://cloud.tencent.com/developer?from=10680) to learn more.
Reference: "How To Install and Use Docker on Ubuntu 16.04"
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