This topic describes how to deploy and use Docker on an Elastic Compute Service (ECS) instance that runs an Alibaba Cloud Linux 3.2104 64-bit operating system. This topic is intended for developers who are familiar with Linux but new to Alibaba Cloud ECS.

Prerequisites

At least one instance that runs an Alibaba Cloud Linux 3.2104 64-bit operating system is created. For more information, see Create an instance by using the wizard.

The following instance configurations are used in the examples:
  • Instance type: ecs.g6.large
  • Operating system: Alibaba Cloud Linux 3.2104 64-bit
  • Network type: Virtual Private Cloud (VPC)
  • IP address: a public IP address

Background information

This topic describes the following operations:
  • Deploy Docker. For more information, see the Deploy Docker section.
  • Use Docker.
    • For information about how to use Docker, see the Use Docker section.
    • For information about how to create a Docker image, see the Create a Docker image section.

Deploy Docker

  1. Remotely connect to an ECS instance. For more information, see Overview.
  2. Install Docker.
    You can use one of the following methods to install Docker:
    • Install the default Docker (podman-docker) in the DNF repository.
      1. Run the following command to install podman-docker:
        dnf -y install docker
      2. Run the following command to check whether Docker is installed:
        docker images
        If a command output similar to the following one is returned, Docker is installed:
        Note podman-docker installed by using this method has no daemon (systemd). Therefore, you can use Docker without the need to pay attention to the running state of podman-docker in subsequent operations. You do not need to run the systemctl command to perform operations.
        podman-docker
    • Install Docker Community Edition (Docker-CE).
      1. Run the following command to add the DNF repository of Docker-CE:
        dnf config-manager --add-repo=https://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo
      2. Run the following command to install the DNF repository plug-in that is dedicated for Alibaba Cloud Linux 3:
        dnf -y install dnf-plugin-releasever-adapter --repo alinux3-plus
      3. Run the following command to install Docker-CE:
        dnf -y install docker-ce --nobest
      4. Run the following command to check whether Docker-CE is installed:
        dnf list docker-ce
        If a command output similar to the following one is returned, Docker-CE is installed: docker-ce
  3. Run the following command to start Docker:
    systemctl start docker
  4. Run the following command to view the running state of Docker:
    systemctl status docker
    If a command output similar to the following one is returned, Docker is in the running state. docker-active

Use Docker

You can use Docker in the following ways:
  • Manage the Docker daemon.
    systemctl start docker     #Run the Docker daemon.
    systemctl stop docker      #Stop the Docker daemon.
    systemctl restart docker   #Restart the Docker daemon.
    systemctl enable docker    #Configure Docker to run on system startup.
    systemctl status docker    #View the running state of Docker.
  • Manage images. In the following example, Apache images from Alibaba Cloud Container Registry are used:
    docker pull registry.cn-hangzhou.aliyuncs.com/lxepoo/apache-php5
    • Modify tags. The names of images from Alibaba Cloud Container Registry are long. Modify the tags of the images to make the images easy to identify.
      docker tag registry.cn-hangzhou.aliyuncs.com/lxepoo/apache-php5:latest aliweb:v1
    • Check existing images.
      docker images
    • Forcibly delete an image.
      docker rmi -f registry.cn-hangzhou.aliyuncs.com/lxepoo/apache-php5
  • Manage containers.
    • Access a container. Run the docker images command to obtain the ImageId value, which is e1abc****. Then, run the docker run command to access the container.
      docker run -it e1abc**** /bin/bash
    • Exit the container. Run the exit command to exit the container.
    • Add the –d parameter to the run command to run the container in the background. The --name parameter specifies apache as the container name.
      docker run -d --name apache e1abc****
    • Access the container that runs in the background.
      docker exec -it apache /bin/bash
    • Query the container ID.
      docker ps
    • Create an image from the container by using the following command syntax: docker commit <Container ID or container name> [<Repository name> [: <Tag>]].
      docker commit containerID/containerName repository:tag
    • To test and restore an image, run the source image, derive a new image that has a simple name from the source image, and then test the new image.
      docker commit 4c8066cd8**** apachephp:v1
    • Run the container and map port 8080 of the host to the container.
      docker run -d -p 8080:80 apachephp:v1
      In a browser, enter the IP address of the instance followed by the port number 8080 to connect to the container. A response similar to the one shown in the following figure indicates that the container runs normally.
      Note An inbound rule must be added to a security group of the ECS instance to allow inbound traffic over port 8080. For more information, see Add security group rules.
      Mapping result

Create a Docker image

  1. Prepare Dockerfile.
    1. Create and edit Dockerfile.
      vim Dockerfile
    2. Press the I key to enter the edit mode. Add the following content to the file:
      #Declare a base image. 
      FROM apachephp:v1
      #Declare the owner of the base image. 
      MAINTAINER DTSTACK
      #Specify the commands that you want to run before the container starts. You must append these commands to the end of the RUN command. Dockerfile can contain only up to 127 lines. If you have commands that exceed 127 lines, we recommend that you write these commands to a script. 
      RUN mkdir /dtstact
      #Specify the commands that are run on system startup. The last command must be a frontend command that runs constantly. Otherwise, the container exits after all commands are run. 
      ENTRYPOINT ping www.aliyun.com
    3. Press the Esc key. Enter :wq and press the Enter key to save and exit Dockerfile.
  2. Create an image.
    docker build -t webalinux3:v1 .          #Use Dockerfile to create an image. . at the end of the command line specifies the path of Dockerfile and must be provided. 
    docker images                            #Check whether the image is created. 
  3. Run the container and check its state.
    docker run -d webalinux3:v1           #Run the container in the background. 
    docker ps                             #Query the containers that are in the running state. 
    docker ps -a                          #Query all containers, including those in the stopped state. 
    docker logs CONTAINER ID/IMAGE        #If the container does not appear in the query results, check the startup log to troubleshoot the issue based on the container ID or name. 
  4. Create an image.
    docker commit fb2844b6**** dtstackweb:v1     #Append the container ID and the name and version number of the new image to the end of the commit parameter. 
    docker images                                #Query images that are downloaded and created on premises. 
  5. Push the image to a remote repository.
    By default, the image is pushed to Docker Hub. You must log on to Docker, add a tag to the image, and then name the image in the <Docker username>/<Image name>:<Tag> format. Then, the image is pushed to the remote repository.
    docker login --username=dtstack_plus registry.cn-shanghai.aliyuncs.com #Enter the password of the image registry after you run this command. 
    docker tag [ImageId] registry.cn-shanghai.aliyuncs.com/dtstack123/test:[Tag]
    docker push registry.cn-shanghai.aliyuncs.com/dtstack123/test:[Tag]