It sounds as if the description you have been given is one that is a teaching convenience for understanding permissions--and it is not quite correct.
What you call the "root level" is comprised of files that live in the file system--which you claim to be "level 2" and separate from them. Thus, that is incorrect.
The "root" is actually the base level of the file system, and thus the "root user" is one who has access and privileges to work with all the files in the system--the system administrator, in other words.
Note that the operating system kernel, which does what you are referring to in your "root" designation, also lives in the filesystem and not "below" it in any way--that is why when installing the OS the first thing it does is format the partitions for the filesystem(s) that will be used. Note, too, that on a UNIX system (or Linux, which is actually "UNIX-like") you can have different file system formats on different partitions--or no format, such as on a swap partition).
The rest of what you described is merely a function of the permissions given to the various classes of users and nothing more. Permissions in UNIX are much more fine-grained than in Windows, since UNIX was designed from the first to be a multi-user operating system.
By contrast, Windows originally was designed for a single user only. Even though the architecture changed greatly with Windows 2000 and newer, much of that heritage continues...but gradually, each successive release of Windows has incorporated more UNIX-like features.
However, the simple fact is that you will get some rather confused looks from Linux or UNIX users when you speak of a "three layer system" in the context that you have here--it is largely meaningless when you confuse permissions with system architecture as you have here.
David
--- In LINUX_Newbies@yahoogroups.com, "Rob" <sun408b@...> wrote:
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> From what I understand.
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> The bottom Layer (the "base" or the "root") is the guts of the operating system. Here are the system files a user never sees, and should never mess with. Here is where input/output is controlled, and how memory and disc access are managed. Nothing here pertains to the normal user. So all these files are locked down and require the highest access level to be able to modify.
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> An administrator will need access here to perform a system update, or add a new feature (second hard drive, new graphics card, whatever). Otherwise it is left alone , So this layer requires root access
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> The middle layer is the file system and the applications/programs. Depending on the way the computer is used and the ability of the user, this layer and the upper layer may use the same access level or they may be split. Assuming the machine is fully compartmented, then a supervisor might have middle level access so he can add and remove programs and change permissions of shared file systems. But he is not a "guru" so he does not have "root" access.
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> The top layer is the user layer. In a locked down machine, the user can open and run programs they are set up for them, store data where the supervisor has designated, and read files they have permissions for. Otherwise, they are locked out of the machine, and cannot change or view areas outside their boundaries.
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> Why does windows not use the 3 layers like Linux ,Unix and Mac OS x?
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> And is all Linux have 3 layer system like Unix and Mac OS X
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