Removing a container removes its writeable layer and all the data in it, so that's not the place to store data if you run a stateful application in a container. The underlying file in the read-only layer is unchanged, so images don't get modified when containers make changes. That layer stores the modified version and hides the original. When processes inside the container modify files from read-only layers, they're actually copied into the writeable layer. The virtual filesystem the container sees is built up of many image layers which are read-only and shared, and a final writeable layer which is unique to the container: It's the basis for how images are shared between multiple containers, and it's the reason why data stored in a container is lost when the container is removed. In reality the C drive is composed of many parts, which Docker assembles into a virtual filesystem.
DOCKER RUN IMAGE MOUNT VOLUME WINDOWS
In a Windows Docker container the filesystem consists of a single C drive, and you'll see all the usual file paths in there - like C:\Program Files and C:\inetpub. Filesystems in Docker ContainersĪn application running in a container sees a complete filesystem, and the process can read and write any files it has access to. Your app writes to the G drive and the runtime happily lets the Windows filesystem take care of actually finding the location, which happens to be a symlink to a directory on the Docker host. You can avoid that issue by using a mapped drive (say G:\) inside the container. This issue may not affect all application runtimes, but I have seen it with Windows Docker containers running Java, Node JS, Go, PHP and.
Some application runtimes try to follow the friendly path to the real location - which is actually outside the container - and get themselves into trouble. Docker uses symbolic links to give the volume a friendly path inside the container, like C:\data.
DOCKER RUN IMAGE MOUNT VOLUME UPDATE
You use Docker volumes to store state outside of containers, so your data survives when you replace the container to update your app. See 6 Things You Can Do with Docker in Windows Server 2019 That You Couldn't Do in Windows Server 2016 Update! From Windows 1809 onwards this is no longer an issue!
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