How to Use docker run -v for Volume Mounting

Use docker run -v host_path:container_path to mount a directory or file from your host machine into the Docker container. This lets the container access or save data directly on your host, making data persistent or shared.

Syntax

The -v option in docker run mounts a volume from the host to the container. The syntax is:

• host_path:container_path - Mounts a directory or file from the host to the container.
• ro (optional) - Mounts the volume as read-only.

bash

docker run -v /path/on/host:/path/in/container image_name

Example

This example mounts the host directory /home/user/data into the container at /app/data. The container can read and write files in this folder, and changes persist on the host.

bash

docker run -it -v /home/user/data:/app/data ubuntu bash

Output

root@container_id:/# ls /app/data
file1.txt  file2.txt

Common Pitfalls

Common mistakes include:

• Using relative paths instead of absolute paths on the host.
• Forgetting to create the host directory before mounting.
• Not specifying ro when you want a read-only mount.
• Permission issues if the container user cannot access the host directory.

bash

docker run -v data:/app/data ubuntu  # Wrong: 'data' is a named volume, not a relative path

docker run -v /home/user/data:/app/data:ro ubuntu  # Right: mounts read-only

Quick Reference

Option	Description	Example
-v host_path:container_path	Mount host directory/file into container	docker run -v /host/data:/container/data ubuntu
-v host_path:container_path:ro	Mount as read-only	docker run -v /host/data:/container/data:ro ubuntu
-v volume_name:container_path	Use named Docker volume	docker run -v myvol:/app/data ubuntu

Key Takeaways

Always use absolute paths for the host directory when using -v.

Mounting volumes shares files between host and container for persistence or data sharing.

Add :ro to mount volumes as read-only to protect host data.

Create host directories before mounting to avoid errors.

Check permissions to ensure the container can access the mounted path.