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选题: 20190520 Getting Started With Docker
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sources/tech/20190520 Getting Started With Docker.md
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sources/tech/20190520 Getting Started With Docker.md
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[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Getting Started With Docker)
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[#]: via: (https://www.ostechnix.com/getting-started-with-docker/)
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[#]: author: (sk https://www.ostechnix.com/author/sk/)
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Getting Started With Docker
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======
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![Getting Started With Docker][1]
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In our previous tutorial, we have explained **[how to install Docker in Ubuntu][2]** , and how to [**install Docker in CentOS**][3]. Today, we will see the basic usage of Docker. This guide covers the Docker basics, such as how to create a new container, how to run the container, remove a container, how to build your own Docker image from the Container and so on. Let us get started! All steps given below are tested in Ubuntu 18.04 LTS server edition.
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### Getting Started With Docker
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Before exploring the Docker basics, don’t confuse with Docker images and Docker Containers. As I already explained in the previous tutorial, Docker Image is the file that decides how a Container should behave, and Docker Container is the running or stopped stage of a Docker image.
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##### 1\. Search Docker images
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We can get the images from either from the registry, for example [**Docker hub**][4], or create our own, For those wondering, Docker hub is cloud hosted place where all Docker users build, test, and save their Docker images.
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Docker hub has tens of thousands of Docker images. You can search for the any Docker images with **“docker search”** command.
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For instance, to search for docker images based on Ubuntu, run:
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```
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$ sudo docker search ubuntu
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```
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**Sample output:**
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![][5]
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To search images based on CentOS, run:
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```
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$ sudo docker search ubuntu
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```
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To search images for AWS, run:
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```
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$ sudo docker search aws
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```
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For wordpress:
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```
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$ sudo docker search wordpress
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```
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Docker hub has almost all kind of images. Be it an operating system, application, or anything, you will find pre-built Docker images in Docker hub. If something you’re looking for is not available, you can build it and make it available for public or keep it private for your own use.
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##### 2\. Download Docker image
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To download Docker image for Ubuntu OS, run the following command from the Terminal:
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```
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$ sudo docker pull ubuntu
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```
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The above command will download the latest Ubuntu image from the **Docker hub**.
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**Sample output:**
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```
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Using default tag: latest
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latest: Pulling from library/ubuntu
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6abc03819f3e: Pull complete
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05731e63f211: Pull complete
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0bd67c50d6be: Pull complete
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Digest: sha256:f08638ec7ddc90065187e7eabdfac3c96e5ff0f6b2f1762cf31a4f49b53000a5
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Status: Downloaded newer image for ubuntu:latest
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```
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![][6]
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Download docker images
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You can also download a specific version of Ubuntu image using command:
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```
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$ docker pull ubuntu:18.04
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```
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Docker allows us to download any images and start the container regardless of the host OS.
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For example, to download CentOS image, run:
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```
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$ sudo docker pull centos
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```
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All downloaded Docker images will be saved in **/var/lib/docker/** directory.
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To view the list of downloaded Docker images, run:
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```
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$ sudo docker images
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```
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**Sample output:**
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```
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REPOSITORY TAG IMAGE ID CREATED SIZE
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ubuntu latest 7698f282e524 14 hours ago 69.9MB
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centos latest 9f38484d220f 2 months ago 202MB
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hello-world latest fce289e99eb9 4 months ago 1.84kB
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```
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As you see above, I have downloaded three Docker images – **Ubuntu** , **CentOS** and **hello-world**.
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Now, let us go ahead and see how to start or run the containers based on the downloaded images.
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##### 3\. Run Docker Containers
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We can start the containers in two methods. We can start a container either using its **TAG** or **IMAGE ID**. **TAG** refers to a particular snapshot of the image and the **IMAGE ID** is the corresponding unique identifier for that image.
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As you in the above results **“latest”** is the TAG for all containers, and **7698f282e524** is the IMAGE ID of **Ubuntu** Docker image, **9f38484d220f** is the image id of CentOS Docker image and **fce289e99eb9** is the image id of **hello_world** Docker image.
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Once you downloaded the Docker images of your choice, run the following command to start a Docker container by using its TAG.
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```
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$ sudo docker run -t -i ubuntu:latest /bin/bash
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```
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Here,
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* **-t** : Assigns a new Terminal inside the Ubuntu container.
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* **-i** : Allows us to make an interactive connection by grabbing the standard in (STDIN) of the container.
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* **ubuntu:latest** : Ubuntu container with TAG “latest”.
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* **/bin/bash** : BASH shell for the new container.
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Or, you can start the container using IMAGE ID as shown below:
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```
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sudo docker run -t -i 7698f282e524 /bin/bash
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```
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Here,
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* **7698f282e524** – Image id
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After starting the container, you’ll be landed automatically into the Container’s shell (Command prompt):
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![][7]
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Docker container’s shell
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To return back to the host system’s Terminal (In my case, it is Ubuntu 18.04 LTS) without terminating the Container (guest os), press **CTRL+P** followed by **CTRL+Q**. Now, you’ll be safely return back to your original host computer’s terminal window. Please note that the container is still running in the background and we didn’t terminate it yet.
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To view the list running of containers, run the following command:
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```
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$ sudo docker ps
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```
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**Sample output:**
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```
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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32fc32ad0d54 ubuntu:latest "/bin/bash" 7 minutes ago Up 7 minutes modest_jones
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```
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![][8]
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List running containers
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Here,
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* **32fc32ad0d54** – Container ID
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* **ubuntu:latest** – Docker image
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Please note that **Container ID and Docker image ID are different**.
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To list all available ( either running or stopped) containers:
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```
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$ sudo docker ps -a
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```
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To stop (power off the container) from the host’s shell, run the following command:
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```
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$ sudo docker stop <container-id>
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```
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**Example:**
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```
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$ sudo docker stop 32fc32ad0d54
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```
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To login back to or attach to the running container, just run:
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```
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$ sudo docker attach 32fc32ad0d54
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```
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As you already know, **32fc32ad0d54** is the container’s ID.
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To power off a Container from inside it’s shell by typing the following command:
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```
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# exit
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```
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You can verify the list of running containers with command:
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```
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$ sudo docker ps
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```
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##### 4\. Build your custom Docker images
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Docker is not just for downloading and using the existing containers. You can create your own custom docker image as well.
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To do so, start any one the downloaded container:
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```
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$ sudo docker run -t -i ubuntu:latest /bin/bash
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```
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Now, you will be in the container’s shell.
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Then, install any software or do what ever you want to do in the container.
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For example, let us install **Apache web server** in the container.
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Once you did all tweaks, installed all necessary software, run the following command to build your custom Docker image:
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```
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# apt update
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# apt install apache2
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```
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Similarly, install and test any software of your choice in the Container.
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Once you all set, return back to the host system’s shell. Do not stop or poweroff the Container. To switch to the host system’s shell without stopping Container, press CTRL+P followed by CTRL+Q.
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From your host computer’s shell, run the following command to find the container ID:
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```
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$ sudo docker ps
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```
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Finally, create a Docker image of the running Container using command:
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```
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$ sudo docker commit 3d24b3de0bfc ostechnix/ubuntu_apache
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```
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**Sample Output:**
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```
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sha256:ce5aa74a48f1e01ea312165887d30691a59caa0d99a2a4aa5116ae124f02f962
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```
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Here,
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* **3d24b3de0bfc** – Ubuntu container ID. As you already, we can
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* **ostechnix** – Name of the user who created the container.
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* **ubuntu_apache** – Name of the docker image created by user ostechnix.
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Let us check whether the new Docker image is created or not with command:
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```
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$ sudo docker images
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```
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**Sample output:**
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```
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REPOSITORY TAG IMAGE ID CREATED SIZE
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ostechnix/ubuntu_apache latest ce5aa74a48f1 About a minute ago 191MB
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ubuntu latest 7698f282e524 15 hours ago 69.9MB
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centos latest 9f38484d220f 2 months ago 202MB
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hello-world latest fce289e99eb9 4 months ago 1.84kB
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```
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![][9]
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List docker images
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As you see in the above output, the new Docker image has been created in our localhost system from the running Container.
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Now, you can create a new Container from the newly created Docker image as usual suing command:
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```
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$ sudo docker run -t -i ostechnix/ubuntu_apache /bin/bash
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```
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##### 5\. Removing Containers
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Once you’re done all R&D with Docker containers, you can delete if you don’t want them anymore.
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To do so, First we have to stop (power off) the running Containers.
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Let us find out the running containers with command:
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```
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$ sudo docker ps
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```
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**Sample output:**
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```
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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3d24b3de0bfc ubuntu:latest "/bin/bash" 28 minutes ago Up 28 minutes goofy_easley
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```
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Stop the running container by using it’s ID:
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```
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$ sudo docker stop 3d24b3de0bfc
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```
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Now, delete the container using command:
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```
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$ sudo docker rm 3d24b3de0bfc
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```
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Similarly, stop all containers and delete them if they are no longer required.
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Deleting multiple containers one by one can be a tedious task. So, we can delete all stopped containers in one go, just run:
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```
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$ sudo docker container prune
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```
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Type **“Y”** and hit ENTER key to delete the containers.
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```
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WARNING! This will remove all stopped containers.
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Are you sure you want to continue? [y/N] y
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Deleted Containers:
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32fc32ad0d5445f2dfd0d46121251c7b5a2aea06bb22588fb2594ddbe46e6564
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5ec614e0302061469ece212f0dba303c8fe99889389749e6220fe891997f38d0
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Total reclaimed space: 5B
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```
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This command will work only with latest Docker versions.
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##### 6\. Removing Docker images
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Once you removed containers, you can delete the Docker images that you no longer need.
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To find the list of the Downloaded Docker images:
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```
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$ sudo docker images
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```
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**Sample output:**
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```
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REPOSITORY TAG IMAGE ID CREATED SIZE
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ostechnix/ubuntu_apache latest ce5aa74a48f1 5 minutes ago 191MB
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ubuntu latest 7698f282e524 15 hours ago 69.9MB
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centos latest 9f38484d220f 2 months ago 202MB
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hello-world latest fce289e99eb9 4 months ago 1.84kB
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```
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As you see above, we have three Docker images in our host system.
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Let us delete them by using their IMAGE id:
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```
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$ sudo docker rmi ce5aa74a48f1
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```
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**Sample output:**
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```
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Untagged: ostechnix/ubuntu_apache:latest
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Deleted: sha256:ce5aa74a48f1e01ea312165887d30691a59caa0d99a2a4aa5116ae124f02f962
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Deleted: sha256:d21c926f11a64b811dc75391bbe0191b50b8fe142419f7616b3cee70229f14cd
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```
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##### Troubleshooting
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Docker won’t let you to delete the Docker images if they are used by any running or stopped containers.
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For example, when I try to delete a Docker Image with ID **b72889fa879c** , from one of my old Ubuntu server. I got the following error:
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```
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Error response from daemon: conflict: unable to delete b72889fa879c (must be forced) - image is being used by stopped container dde4dd285377
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```
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This is because the Docker image that you want to delete is currently being used by another Container.
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So, let us check the running Container using command:
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```
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$ sudo docker ps
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```
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**Sample output:**
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![][10]
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Oops! There is no running container.
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Let us again check for all containers (Running and stopped) with command:
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```
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$ sudo docker ps -a
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```
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**Sample output:**
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![][11]
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As you see there are still some stopped containers are using one of the Docker images. So, let us delete all of the containers.
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**Example:**
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```
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$ sudo docker rm 12e892156219
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```
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Similarly, remove all containers as shown above using their respective container’s ID.
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Once you deleted all Containers, finally remove the Docker images.
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**Example:**
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```
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$ sudo docker rmi b72889fa879c
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```
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That’s it. Let us verify is there any other Docker images in the host with command:
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```
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$ sudo docker images
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```
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For more details, refer the official resource links given at the end of this guide or drop a comment in the comment section below.
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Also, download and use the following Docker Ebooks to get to know more about it.
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|
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** **Download** – [**Free eBook: “Docker Containerization Cookbook”**][12]
|
||||
|
||||
** **Download** – [**Free Guide: “Understanding Docker”**][13]
|
||||
|
||||
** **Download** – [**Free Guide: “What is Docker and Why is it So Popular?”**][14]
|
||||
|
||||
** **Download** – [**Free Guide: “Introduction to Docker”**][15]
|
||||
|
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** **Download** – [**Free Guide: “Docker in Production”**][16]
|
||||
|
||||
And, that’s all for now. Hope you a got the basic idea about Docker usage.
|
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|
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More good stuffs to come. Stay tuned!
|
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|
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Cheers!!
|
||||
|
||||
--------------------------------------------------------------------------------
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||||
|
||||
via: https://www.ostechnix.com/getting-started-with-docker/
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||||
|
||||
作者：[sk][a]
|
||||
选题：[lujun9972][b]
|
||||
译者：[译者ID](https://github.com/译者ID)
|
||||
校对：[校对者ID](https://github.com/校对者ID)
|
||||
|
||||
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
|
||||
|
||||
[a]: https://www.ostechnix.com/author/sk/
|
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[b]: https://github.com/lujun9972
|
||||
[1]: https://www.ostechnix.com/wp-content/uploads/2016/04/docker-basics-720x340.png
|
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[2]: http://www.ostechnix.com/install-docker-ubuntu/
|
||||
[3]: https://www.ostechnix.com/install-docker-centos/
|
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[4]: https://hub.docker.com/
|
||||
[5]: http://www.ostechnix.com/wp-content/uploads/2016/04/Search-Docker-images.png
|
||||
[6]: http://www.ostechnix.com/wp-content/uploads/2016/04/Download-docker-images.png
|
||||
[7]: http://www.ostechnix.com/wp-content/uploads/2016/04/Docker-containers-shell.png
|
||||
[8]: http://www.ostechnix.com/wp-content/uploads/2016/04/List-running-containers.png
|
||||
[9]: http://www.ostechnix.com/wp-content/uploads/2016/04/List-docker-images.png
|
||||
[10]: http://www.ostechnix.com/wp-content/uploads/2016/04/sk@sk-_005-1-1.jpg
|
||||
[11]: http://www.ostechnix.com/wp-content/uploads/2016/04/sk@sk-_006-1.jpg
|
||||
[12]: https://ostechnix.tradepub.com/free/w_java39/prgm.cgi?a=1
|
||||
[13]: https://ostechnix.tradepub.com/free/w_pacb32/prgm.cgi?a=1
|
||||
[14]: https://ostechnix.tradepub.com/free/w_pacb31/prgm.cgi?a=1
|
||||
[15]: https://ostechnix.tradepub.com/free/w_pacb29/prgm.cgi?a=1
|
||||
[16]: https://ostechnix.tradepub.com/free/w_pacb28/prgm.cgi?a=1
|
||||
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