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Context - I'd like to benefit from docker layer caching for the shared caches. There's a trick you can do to get layer caching for the shared caches by copying across all the `*.gradle` etc files in one `COPY` which prevents the layer cache being invalidated unless you change one of those files:
<https://github.com/Mahoney/lidalia-shell/blob/8a1f16960ff303512d02ecc3f2caeb35ed99fae0/Dockerfile#L42-L44>

However, in order to benefit from the build cache when building locally you need to use the new `RUN --mount=type=cache,target=&lt;cache_dir&gt;` directive. If you point that at `~/.gradle/caches` then you lose all the layer caching.

GRADLE_USER_HOME <https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_environment_variables|https://docs.gradle.org/current/userguide/build_environment.html#sec:gradle_environment_variables>
-g, --gradle-user-home <https://docs.gradle.org/current/userguide/command_line_interface.html#sec:environment_options|https://docs.gradle.org/current/userguide/command_line_interface.html#sec:environment_options>

Won't that just move where the `caches` dir is?

share nothing except <https://docs.gradle.org/current/userguide/dependency_resolution.html#sub:ephemeral-ci-cache|https://docs.gradle.org/current/userguide/dependency_resolution.html#sub:ephemeral-ci-cache>

&gt; does that not accomplish what you want?
No, I don't think it does.

I'm building a multi-stage Dockerfile, so I can't mount a directory, I can only benefit from layer caching of the `/root/.gradle/caches/modules-2` directory.

I want to use the `RUN --mount=type=cache,target=&lt;cache_dir&gt;` directive so that repeat local `docker build .` calls benefit from build caching, which I think means that `&lt;cache_dir&gt;` has to be `/root/.gradle/caches` (if running `FROM` a container using the root user).

That blows away any layer cache inside `/root/.gradle/caches/modules-2`.

I might be able to benefit by running `RUN --mount=type=cache,target=/root/.gradle/caches/7.4.2` but having to duplicate the gradle version in that path is just obviously going to be a maintenance fail.

My imagination is failing me as to how unfortunately.

Not for the first time I feel like I'd really like to get a Gradle expert &amp; a Docker expert in the same room to thrash out the best way to write a multi-stage Dockerfile that builds a Gradle project efficiently both locally and on GitHub Actions or similar.

I must have spent weeks wrestling with this over the last couple of years.

&gt; My imagination is failing me as to how unfortunately.
Make a directory that you configure for that caching thing.
Move the files / directories to be cached in there.
Symlink the moved files / directories to the original places within Gradle user home