Qian Zhang created MESOS-6360:
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Summary: The handling of whiteout files in provisioner is not
correct
Key: MESOS-6360
URL: https://issues.apache.org/jira/browse/MESOS-6360
Project: Mesos
Issue Type: Bug
Reporter: Qian Zhang
Assignee: Qian Zhang
Currently when user launches a container from a Docker image via universal
containerizer, we always handle the whiteout files in
{{ProvisionerProcess::__provision()}} after the Docker image is pulled by
puller/fetcher and the rootfs for the container is provisioned by backend.
However this is actually not correct, because the way to handle whiteout files
is backend dependent, that means for different backends, we need to handle
whiteout files in different ways, e.g.:
* AUFS backend: It seems the AUFS whiteout ({{.wh.<filename/dirname>}} and
{{.wh..wh..opq}}) is the whiteout standard in Docker (see [this comment |
https://github.com/docker/docker/blob/v1.12.1/pkg/archive/archive.go#L259:L262]
for details), so that means after the Docker image is pulled, the whiteout
files in the store in it are already in aufs format, then we do not need to do
anything about whiteout file handling because the aufs mount done in
{{AufsBackendProcess::provision()}} will handle it automatically.
* Overlay backend: Overlayfs has its own whiteout files (see [this doc |
https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt] for
details), so we need to convert the aufs whiteout files to overlayfs whiteout
files before we do the overlay mount in {{OverlayBackendProcess::provision}}
which will automatically handle the overlayfs whiteout files.
* Copy backend: We need to manually handle the aufs whiteout files when we copy
each layer in {{CopyBackendProcess::_provision()}}.
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