301 — Docker Volumes and Data Persistence

Master data persistence in Docker using volumes, bind mounts, and tmpfs. Learn to manage stateful applications and share data between containers.

Learning Objectives

Understand container filesystem vs persistent storage

Create and manage Docker volumes

Use bind mounts for development workflows

Share data between multiple containers

Back up and restore volume data

Step 1

Understanding container ephemeral storage

See how container data disappears when containers are removed.

Commands to Run

docker run --name temp-container ubuntu bash -c 'echo "Important data" > /data.txt && cat /data.txt'

docker start temp-container

docker exec temp-container cat /data.txt

docker rm -f temp-container

docker run --name temp-container ubuntu cat /data.txt

What This Does

Container filesystems are ephemeral. Data created inside a container is lost when the container is removed. Each new container starts fresh from the image.

Expected Outcome

First container shows the data. After removal, new container with same name can't find /data.txt - the file is gone.

Pro Tips

1
Container layers are temporary by default
2
Data persists while container exists (even when stopped)
3
Removing the container destroys its filesystem layer
4
Use volumes for data that must survive container lifecycle

Common Mistakes to Avoid

⚠️Assuming data inside containers is permanent
⚠️Losing important data by removing containers
⚠️Not planning for data persistence from the start