Bind mounts

Share a host folder with a bind mount

A bind mount links a specific folder on your computer directly into a container. Whatever is in that folder appears inside the container, and changes flow both ways in real time.

This is different from a volume:

• A volume is storage Docker manages somewhere internal - you don't pick a folder on your disk.
• A bind mount points at an exact folder you choose on your machine.

Why it's great for development

Imagine you're developing an app inside a container, but you want to edit the code with your normal editor on your computer. With a bind mount, you edit files on your machine and the container sees the changes immediately - no rebuild needed.

The syntax is the same -v flag, but instead of a volume name you give a path on your computer:

docker run -it -v "$(pwd):/app" -w /app node bash

Breaking it down:

• "$(pwd)" is your current folder on your computer. (On Windows PowerShell you can use ${PWD} instead.)
• :/app mounts it at /app inside the container.
• -w /app sets the working directory to /app (same idea as WORKDIR, but as a run-time flag).

Now /app inside the container is your project folder. Edit a file on your computer, and the running container sees the new version instantly.

Volumes vs bind mounts - which to use

A simple guideline:

• Use a volume for data the container owns and should persist (databases, uploads managed by the app).
• Use a bind mount to share your source code into a container during local development.

You now know how to keep and share data. Next, we'll connect containers to the outside world and to each other with networking.

The path gotcha on Windows and macOS

Bind mounts need an absolute path, and this is where beginners get stuck. $(pwd) handles it on Linux and macOS; in PowerShell on Windows use ${PWD}. If you pass a relative path or get the quoting wrong, you'll either see an error or - worse - an empty folder mounted over your files. When a bind mount "loses" your files, the path is almost always the culprit. Double-check it's absolute and correctly quoted.

FAQ

When should I use a bind mount instead of a volume?

Use a bind mount during development, to share your source code from your computer into the container so edits show up live. Use a volume for data the container should own and persist, like a database.

Why are my files empty inside the bind mount?

Usually a wrong or relative host path, so Docker mounts the wrong (empty) folder over your target. Make sure the host path is absolute - $(pwd) on Linux/macOS or ${PWD} in Windows PowerShell.

Do bind mount changes sync both ways?

Yes. A bind mount is a live link: edit a file on your computer and the container sees it instantly, and files the container writes appear on your computer too.