COPY instruction for adding files in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the COPY instruction do in a Dockerfile?

The COPY instruction copies files or directories from the build context on your computer into the Docker image at a specified path.

beginner

How do you copy a single file named app.py from your local folder to the Docker image's /app directory?

Use the instruction: <br>COPY app.py /app/

intermediate

Can the COPY instruction copy multiple files or folders at once?

Yes, you can copy multiple files or folders by listing them separated by spaces before the destination path, for example: <br>COPY file1.txt file2.txt /app/

intermediate

What happens if the destination folder in COPY does not exist inside the image?

Docker will create the destination folder automatically before copying the files.

intermediate

What is the difference between COPY and ADD instructions in Docker?

COPY only copies files and folders from the build context. ADD can also extract compressed files and fetch files from URLs, but COPY is preferred for simple copying because it is more predictable.

Which Dockerfile instruction copies files from your computer into the image?

A RUN

B COPY

C CMD

D EXPOSE

COPY is used to copy files or directories from your local build context into the Docker image.

What happens if the destination folder in COPY does not exist?

A The build fails with an error

B Docker ignores the COPY instruction

C Files are copied to the root folder instead

D Docker creates the folder automatically

Docker creates the destination folder if it does not exist before copying files.

How do you copy multiple files in one COPY instruction?

A List all files separated by spaces before the destination

B Use multiple COPY instructions

C Use a wildcard * only

D You cannot copy multiple files at once

You can list multiple files separated by spaces before the destination path in one COPY instruction.

Which instruction is preferred for simple file copying in Dockerfiles?

A COPY

B ADD

C RUN

D ENV

COPY is preferred for simple copying because it is more predictable and only copies files.

Can COPY fetch files from a URL?

A Only if the URL is inside the image

B Yes, COPY can fetch from URLs

C No, COPY only copies from local build context

D Yes, but only for HTTPS URLs

COPY cannot fetch files from URLs; ADD can do that, but COPY only copies local files.

Explain how the COPY instruction works in a Dockerfile and when you would use it.

Think about how you move files into a container image during build.

Describe the difference between COPY and ADD instructions in Dockerfiles.

Consider extra features ADD has beyond copying.