什么叫根文件系统,它的作用是什么?
什么叫根文件系统,它的作用是什么?如果我要作一个根文件系统，是不是把相应文件夹与文件放进去就行了？

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Linux引导启动时，默认使用的文件系统是根文件系统。其中一般都包括这样一些子目录：
/etc/, /dev/, /usr/, /usr/bin/, /bin/, /var/等。etc/目录主要含有一些系统配置文件；dev/含有设备特殊文件，用于使用文件操作语句操作设备；/usr/存放库函数、手册和其它一些文件。bin/存放执行程序；var/用于存放系统运行时可变的数据或者是日志等信息。

我就知道这些
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简单来说，就是系统第一个mount的文件系统

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.[*]