The complete process of Docker image creation

Preface

Taking the creation of a CentOS image as an example, this article describes the process of image customization, packaging, and pushing to a remote repository. The steps are relatively simple and you can get started quickly.

Creation steps

Create a CentOS base image

Create a build directory and Dockerfile, and edit image-related settings in the Dockerfile.

echo "Create directory docker/build/centos_7.8.2003 in the current user directory" > /dev/null
mkdir -p ~/docker/build/centos_7.8.2003

echo "Create Dockerfile to ~/docker/build/centos_7.8.2003 directory" > /dev/null
cat > ~/docker/build/centos_7.8.2003/Dockerfile << EOF 
# Specify the base image FROM centos:7.8.2003

# Set environment variable ENV LANG=zh_CN.UTF-8 \\
    LANGUAGE=zh_CN:zh \\
    LC_ALL=zh_CN.UTF-8

# Only execute these shell commands when building the image RUN yum update -y && \\
    yum reinstall -y glibc-common && \\
    yum install -y telnet net-tools && \\
    yum clean all && \\
    rm -rf /tmp/* rm -rf /var/cache/yum/* && \\
    localedef -c -f UTF-8 -i zh_CN zh_CN.UTF-8 && \\
    ln -sf /usr/share/zoneinfo/Asia/Shanghai /etc/localtime
EOF

Refer to the Novice Tutorial - docker build to build an image. The format is docker build -t <鏡像名>:<鏡像版本號> <Dockerfile所在目錄> . If the image version number is not specified, the default is latest .

# Parse ~/docker/build/centos_7.8.2003/Dockerfile to build a mirror named base-centos docker build -t base-centos ~/docker/build/centos_7.8.2003

After the build is complete, you can see the base image used and the new image generated by the build in the local image list.

docker images 

Create a container and customize it

Use the new image to create and enter a container. This container is a virtual CentOS system.

echo "Create a container using the base-centos image and name it base-centos" > /dev/null
docker run \
--name base-centos \
--privileged=true \
-dit \
base-centos \
/usr/sbin/init

echo "Enter centos container" > /dev/null
docker exec -it base-centos /bin/bash

Customize the virtual system in the container, such as installing commonly used tools. In fact, these can also be written in the Dockerfile and defined after the RUN instruction.

echo "vim: Edit file" > /dev/null
yum install -y vim

echo "lsof: convenient for viewing port information" > /dev/null
yum install -y lsof

echo "wget: file download" > /dev/null
yum install -y wget

echo "tree: View directory structure" > /dev/null
yum install -y tree

echo "install python" > /dev/null
yum install -y python-devel

echo "C compilation environment" > /dev/null
yum install -y gcc gcc-c++
yum install -y zlib
yum install -y zlib-devel
yum install -y tcl build-essential tk gettext

Create a new image with a custom container

The command format is docker commit <容器名稱或者ID> <生成的鏡像名>:<鏡鏡像版本號> . If the image version number is not written, the default is latest . This container can also be in a stopped state when created.

docker commit base-centos centos:7.8.2003_v1

At this point, the image is created and you can see the new image in the image list.

Save and load the image tarball

Save the image as a tarball in the format of docker save -o <文件名> <鏡像名>:<鏡像標簽> , refer to the novice tutorial - docker save.

docker save -o ~/docker/build/centos_7.8.2003/centos_7.8.2003.tar centos:7.8.2003_v1 

Load the tarball to generate the image.

docker load --input ~/docker/build/centos_7.8.2003/centos_7.8.2003.tar

The load command is invalid if a duplicate image already exists.

Push the image to the remote repository

Docker logs in to the remote warehouse. The format is docker login --username=<用戶名> <倉庫地址> or docker login -u <用戶名> -p <密碼> <倉庫地址> .

docker tag <鏡像ID> <遠程鏡像倉庫地址>:<鏡像版本號> tag.

echo "Mark image address and version number" > /dev/null
docker tag 66b1bc81e1f2 registry.cn-shanghai.aliyuncs.com/exposure/centos:7.8.2003_v1

docker push <遠程鏡像倉庫地址>:<鏡像版本號> pushes to the remote repository.

echo "Push to remote repository" > /dev/null
docker push registry.cn-shanghai.aliyuncs.com/exposure/centos:7.8.2003_v1

Reference Links

CSDN - Several Common CentOS7 Images for Docker

Novice Tutorial - Docker Commands

This is the end of this article about the complete process of Docker image creation. For more relevant content about Docker image creation, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!