Master Docker: Install, Accelerate, and Manage Images on CentOS & Ubuntu

Introduction

This article gives a detailed walkthrough of Docker installation, image acceleration, and image management on Linux distributions, primarily CentOS and Ubuntu.

Install Docker on CentOS

Ensure the kernel version is higher than 3.10, then run the following commands as root: uname -r Update the system and remove any old Docker packages:

sudo yum update</code>
<code>sudo yum remove docker docker-common docker-selinux docker-engine

Install required utilities:

sudo yum install -y yum-utils device-mapper-persistent-data lvm2

Add a repository (official, Alibaba Cloud, or Tsinghua University):

sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo</code>
<code>sudo yum-config-manager --add-repo http://mirrors.aliyun.com/docker-ce/linux/centos/docker-ce.repo</code>
<code>sudo yum-config-manager --add-repo https://mirrors.tuna.tsinghua.edu.cn/docker-ce/linux/centos/docker-ce.repo

Install Docker CE: sudo yum install docker-ce Start Docker and enable it at boot:

sudo systemctl start docker</code>
<code>sudo systemctl enable docker

Verify the installation:

docker version

Install Docker on Ubuntu

Docker CE supports Ubuntu 14.04 (Artful 17.10 Edge+), 16.04 LTS, and 14.04 LTS. Install prerequisites and remove old versions: sudo apt-get remove docker docker-engine Use the official convenience script for quick installation:

curl -fsSL get.docker.com -o get-docker.sh</code>
<code>sudo sh get-docker.sh --mirror AzureChinaCloud

Start and enable Docker:

sudo systemctl enable docker</code>
<code>sudo systemctl start docker

Docker Image Accelerators

Because pulling images from Docker Hub can be slow in China, configure a registry mirror. Examples include Docker’s official China mirror, Alibaba Cloud, and DaoCloud. The article shows how to set up the Alibaba Cloud mirror.

For upstart‑based systems (e.g., Ubuntu 14.04, Debian 7): edit /etc/default/docker and add:

DOCKER_OPTS="--registry-mirror=https://xxxx.mirror.aliyuncs.com"

Then restart Docker: sudo service docker restart For systemd‑based systems (Ubuntu 16.04+, Debian 8+, CentOS 7): create or edit /etc/docker/daemon.json:

{
  "registry-mirrors": ["https://xxxx.mirror.aliyuncs.com"]
}

Reload and restart Docker:

sudo systemctl daemon-reload</code>
<code>sudo systemctl restart docker

Managing Docker Images

Pull an image: docker pull ubuntu:16.04 List images: docker image ls Show only IDs: docker image ls -q Filter images (e.g., dangling, by repository, before a tag):

docker image ls -f dangling=true</code>
<code>docker image ls ubuntu</code>
<code>docker image ls -f since=mongo:3.2

Delete images by ID, name, or digest:

docker image rm 501</code>
<code>docker image rm centos</code>
<code>docker image rm node@sha256:b4f0e0bde...

Understanding Untagged vs Deleted : Untagged removes a tag; Deleted removes the underlying image data when no tags remain.

Special Considerations for CentOS/RHEL

CentOS/RHEL lack native UnionFS drivers, so Docker defaults to the devicemapper driver with a loop‑LVM setup, which has performance and stability drawbacks. It is recommended to configure direct‑LVM for better reliability and space utilization.

Images and Layers

Docker images consist of multiple layers. The size shown by docker image ls is the uncompressed size on disk, which can differ from the compressed size shown on Docker Hub. Layers are shared between images, so total disk usage may be lower than the sum of listed sizes.

Dangling images ( <none>) appear after a newer version of a tag is pulled; they can be removed with: docker image prune Intermediate layers are shown with -a and should not be removed manually because other images may depend on them.

Running a Container

Example of running an interactive Ubuntu container: docker run -it --rm ubuntu:16.04 bash Inside the container you can inspect the OS release file:

cat /etc/os-release

Conclusion

Following this guide enables you to install Docker on major Linux distributions, accelerate image pulls with regional mirrors, and efficiently manage images and containers using Docker’s command‑line tools.