Master Docker Data Persistence: Volumes, Bind Mounts, and Tmpfs Explained

Introduction

In Docker, a container’s read/write data resides in its storage layer and is lost when the container is removed. To achieve persistence, data must be mounted from the host. Docker offers three mounting methods: Volume, bind mounts, and tmpfs mounts.

1. Volume Basic Usage

1.1 Create a Volume

docker volume create for_nginx
docker volume ls
docker volume inspect for_nginx

The created volume for_nginx is stored under /var/lib/docker/volumes/for_nginx/_data on the host.

1.2 Mount the Volume to a Container

docker run -itd -p 88:80 --mount type=volume,source=for_nginx,target=/usr/share/nginx/html nginx

The source specifies the host volume, and target specifies the mount point inside the container.

1.3 Modify the Nginx Homepage

cd /var/lib/docker/volumes/for_nginx/_data/
echo "Hello world" > index.html

1.4 Test Access

Access the Nginx page at http://localhost:88 to see the updated content.

1.5 Verify Persistence

docker rm -f <container_id>
cat /var/lib/docker/volumes/for_nginx/_data/index.html

The data remains after the container is removed, proving that volumes are independent of container lifecycle.

1.6 Clean Up the Volume

docker volume rm for_nginx

2. Bind Mounts Basic Usage

2.1 Run a Container with a Bind Mount

docker run -itd -p 81:80 --mount type=bind,source=/webapp,target=/usr/share/nginx/html nginx

This command is equivalent to the legacy syntax:

docker run -itd -p 81:80 -v /webapp:/usr/share/nginx/html nginx

2.2 Verify the Mount

2.3 Enter the Container

docker exec -it <container_id> /bin/bash
cd /usr/share/nginx/html
ls

When a bind mount targets a non‑empty directory inside the container, the original files are hidden and the container sees only the host’s files, which is the key difference from volumes.

3. Tmpfs Mounts Usage

3.1 Run a Container with a Tmpfs Mount

docker run -itd --mount type=tmpfs,target=/test ubuntu:18.04

3.2 Write Data Inside the Container

docker exec -it <container_id> /bin/bash
cd /test
echo 123123 > tmp.txt
cat tmp.txt

3.3 Restart the Container and Observe Data Loss

docker restart <container_id>
docker exec -it <container_id> /bin/bash
cd /test
cat tmp.txt

The file disappears because tmpfs stores data only in host memory and is removed when the container stops.

3.4 When to Use Tmpfs

Tmpfs is suitable for scenarios where data should not be persisted to disk for security or performance reasons.