Using Docker to Build and Manage a CentOS 7 Linux Virtual Machine

Docker is an open‑source container engine written in Go that provides process‑level sandboxing with minimal performance overhead, allowing multiple containers to share the same CPU and memory resources.

The article demonstrates how to use Docker to create a Linux virtual machine based on a CentOS 7 image, covering image download, container startup, port and volume mapping, image export, and import for environment migration.

Download Image

CentOS image repository: https://hub.docker.com/_/centos?tab=tags&page=1

Command to pull the image:

docker pull centos:7

After pulling, verify with docker images to see the docker.io/centos entry.

Run Container

Start a container from the downloaded image:

docker run -itd --name centos-test -p 4749:4749 -v /data/test/www:/data/www docker.io/centos:7 /sbin/init

Use docker ps -a to confirm the container (e.g., centos-test ) is running.

Enter Container

To access the running container’s shell:

docker exec -it centos7-test /bin/bash

This opens an interactive Bash session inside the CentOS 7 environment.

Export Container as Image

Export the container’s filesystem to a tar archive for migration:

docker export -o centos7-back.tar d4480dc94cdd

The resulting centos7-back.tar file contains the exported image.

Import Image

Import the tar archive back into Docker as a new image:

cat centos7-back.tar | docker import - centos7-back.tar

Verify the new image with docker images ; the imported image appears as centos7-back.tar .

Conclusion

Compared with traditional VMs (e.g., Vagrant, VMware) that partition hardware resources, Docker containers are lightweight, share host resources efficiently, and simplify environment replication across hosts.