下面是从Undertanding the linux kernel 3rd摘录的
12.4. Filesystem Handling
Like every traditional Unix system, Linux makes use of
a system 's root filesystem : it is the filesystem
that is directly mounted by the kernel during the
booting phase and that holds the system initialization
scripts and the most essential system programs.
Other filesystems can be mountedeither by the
initialization scripts or directly by the userson
directories of already mounted filesystems. Being a tree
of directories, every filesystem has its own root
directory. The directory on which a filesystem is
mounted is called the mount point. A mounted filesystem
is a child of the mounted filesystem to which the
mount point directory belongs. For instance, the /proc
virtual filesystem is a child of the system 's root
filesystem (and the system 's root filesystem is the
parent of /proc). The root directory of a mounted
filesystem hides the content of the mount point
directory of the parent filesystem, as well as the
whole subtree of the parent filesystem below the mount
point.
简单的来说，我认为根文件系统就是一种目录结构,那么根文件系统和普通的文件系统有什么区别呢？我认为根文件系统就是要包括Linux启动时所 必须的目录和关键性的文件，例如Linux启动时都需要有init目录下的相关文件，在Linux挂载分区时Linux一定会找/etc/fstab这个 挂载文件等，根文件系统中还包括了许多的应用程序bin目录等，任何包括这些Linux系统启动所必须的文件都可以成为根文件系统。