如何在Dockerfile中移除父镜像声明的卷？测试镜像场景需求

Great question—let's break this down into two parts since you've got a couple of related issues here:

1. Can you remove a Volume declared in a parent Docker image? #

Short answer: You can't directly remove or override a parent image's VOLUME declaration in your child Dockerfile. Once a VOLUME is defined in a parent image, it becomes part of the image's metadata and is inherited by all child images—Docker doesn't provide a way to undo this during the build process.

That said, you have two solid workarounds to achieve your goal of embedding test data directly into the image (avoiding expensive entrypoint data population):

Workaround 1: Recreate the parent image without the VOLUME #

If you have access to the parent image's Dockerfile, copy its entire content into a new Dockerfile, then remove the VOLUME instruction related to the database directory. Use this modified "base" image as the foundation for your test image.

This works because without the VOLUME marker, the database directory behaves like any other directory in the image. You can then copy your test data directly into it during the build stage:

# Modified parent image (no VOLUME for /var/lib/mydb)
FROM my-custom-base-image
# Copy your pre-built test data into the database directory
COPY my-test-db-data/ /var/lib/mydb/
# Set proper permissions if needed
RUN chown -R db-user:db-group /var/lib/mydb

Now when you run a container from this test image, the data is baked into the image layers—no external Volume will override it, and you skip the entrypoint data load.

Workaround 2: Use an alternative directory for test data #

If recreating the parent image isn't feasible, adjust your application's configuration to read data from a new directory (one not marked as a VOLUME in the parent image). Then copy your test data into this new directory during build:

FROM original-parent-image
# Copy test data to a non-VOLUME directory
COPY my-test-db-data/ /var/lib/test-mydb/
# Modify app config to use the new directory (example for a config file)
RUN sed -i 's/\/var\/lib\/mydb/\/var\/lib\/test-mydb/g' /etc/myapp/config.conf

2. Why your mkdir .ssh command isn't persisting #

Chances are this is directly related to the parent image's VOLUME. If the .ssh directory you're trying to create is located inside a path marked as a VOLUME in the parent image, any changes you make to that path during the build stage will be ignored when the container starts.

Docker initializes VOLUME directories when a container launches—even if the image has content in that path, the Volume will mount over it, replacing the build-stage content with an empty (or externally mounted) directory.

To fix this:

• Either follow the workarounds above to remove/avoid the VOLUME for that path
• Or create the .ssh directory in a location outside the parent's VOLUME paths, then update your application to use that new location.

内容的提问来源于stack exchange，提问作者Andy