containers storage项目

_storage _is a Go library which aims to provide methods for storing filesystem
layers, container images, and containers.

drivers目录，列出了所有支持的文件系统，比较常见的是overlay。

研究一下vfs的实现：是基于整个root fs目录复制的形式，当前layer会复制parent layer的全部文件。

github.com/containers/storage/drivers/driver_linux.go
可以看到vfs是优先级最低的driver。

    priority = []string{
        "overlay",
        // We don't support devicemapper without configuration
        // "devicemapper",
        "aufs",
        "btrfs",
        "zfs",
        "vfs",
    }