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by swap32 3510 days ago
>> Data written in the container is persisted to disk

Even if you don't mount any folder from the disk onto the container? Are you sure? Then everything I know about containers is just wrong.
2 comments
vel0city 3510 days ago
I think there's a bit of mix up between what an image is and what a container is. You normally don't write data to an image, but you can write data to the container. You can keep this data so long as you keep the container, and you can commit that container's data to the image if you wish.

I've found a good place to visualize how the filesystems work was this blog: http://merrigrove.blogspot.com/2015/10/visualizing-docker-co...

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cpuguy83 3510 days ago
Yes. The filesystem in the container is a real filesystem backed by the disk.

How this happens is dependent on the storage driver used. The `aufs` driver (default when available), as well as `overlay(2)` and `vfs` drivers just sit on top of the existing filesystem at `/var/lib/docker` (or the defined docker root). BTRFS, ZFS, and devicemapper must be pre-configured to even use and depends on how you configure these, but still generally would be on an actual disk.

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