Using COPY --chown instead of RUN chown in a Dockerfile has several advantages that can lead to more efficient and secure Docker images. 

1. Single Layer Operation
When you use COPY --chown, the change of ownership is applied during the copy process itself, resulting in a single layer in the Docker image. In contrast, using RUN chown involves two steps:

COPY (creates one layer)

# Create a user

RUN adduser -D myuser



# Copy files with ownership change in one step

COPY --chown=myuser:myuser myapp /home/myuser/myapp

RUN chown (creates another layer)
# Create a user

RUN adduser -D myuser



# Copy files first

COPY myapp /home/myuser/myapp



# Change ownership in a separate step

RUN chown -R myuser:myuser /home/myuser/myapp


Each layer in a Docker image increases its size and complexity. By reducing the number of layers, you can create more efficient images that are faster to build and pull.

Conclusion
Using COPY --chown is a more efficient, secure, and streamlined way to manage file ownership in Docker images. It simplifies Dockerfile maintenance, reduces image size, improves build performance, and enhances security by minimizing the number of operations performed within the container.