# Docker Building images

**Building** creates an image from a Dockerfile. Run `docker build -t <name> .` to build from the Dockerfile in the current directory. The `.` is the **build context**: the files Docker has access to for `COPY` instructions. Keep large files out of it using `.dockerignore`.

```bash
$ docker build -t myapp:latest .        # build and tag
$ docker build -t myapp:1.0 -f Dockerfile.prod . # custom Dockerfile
$ docker build --no-cache -t myapp .    # rebuild without using cache
```

Docker sends the entire build context to the daemon on every build, so large build contexts slow builds. Use `.dockerignore` to exclude files (like `.git/`, `node_modules/`, etc.). Builds fail if the Dockerfile has errors or if a `RUN` command exits with a non-zero status.