How to Build Custom Docker Images Manually: From CentOS to Nginx

1. Methods to create Docker images

Use docker commit command

Use docker build with a Dockerfile (recommended)

Although docker commit can capture a running container as an image, a Dockerfile provides far more flexibility and power.

2. Manually building an image

Typically you start from an existing base image such as centos, install the needed software, adjust configuration, and then commit the container as a new image.

Example: Build a custom Nginx image manually

docker pull centos
docker run -it --name mynginx centos
rpm -ivh http://mirrors.aliyun.com/epel/epel-release-latest-7.noarch.rpm
yum install nginx -y
vi /etc/nginx/nginx.conf   # set "daemon off;"
exit
docker commit -m "nginx test mirror" eadfe0c0903d jkzhao/mynginx:v1
docker run -d -p 82:80 jkzhao/mynginx:v1 nginx

Important notes:

You must tag the image with v1; otherwise Docker will look for the latest tag.

The final nginx argument is the command executed inside the container; ensure you use the correct path if not using the default installation.