dockerPreloader fails due to "read-only file system" error

[thefloweringash]

Attempting to use the virtualisation.dockerPreloader feature on current master (6e38def) fails to start containers on the preloaded images. The existing test in nix-build nixos/tests/docker-preloader.nix reproduces the error.

Log message from running the tests on hydra:

docker# [   12.601197] dockerd[747]: time="2019-11-24T18:47:45.973722725Z" level=error msg="Handler for POST /v1.40/containers/create returned error: open /var/lib/docker/overlay2/bcc596043c9e8253025a4cfae4a12eafd168c13342898e60345669e7b453225f/committed: read-only file system"
docker# /nix/store/rbhcr27bx53hqwx72rjkgbj5pfn7jix3-docker-19.03.4/libexec/docker/docker: Error response from daemon: open /var/lib/docker/overlay2/bcc596043c9e8253025a4cfae4a12eafd168c13342898e60345669e7b453225f/committed: read-only file system.

Looking at recent builds, it looks like it's been failing consistently for a while.

cc @nlewo as the author of the module

Maintainer information:

module:
 - virtualisation/docker-preloader.nix

[thefloweringash]

Wild speculation: moby/moby@477bf1e looks suspicious.

[stale]

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[thefloweringash]

The feature is still present and the tests are still failing on hydra. Ideally we should fix the feature, but If the feature can't be supported any more we should remove it. Keeping the issue open until one of these things happens.

[flokli]

#93791 removes docker-preloader.

[flokli]

With #93791 merged, let's close this issue.