Hi,

In root file system hierarchy there are many folders which include data stored in solid state devices and other binaries or libraries in which some may not need to be loaded any time and also some other configuration files.

My doubt is what are the contents that will be loaded to RAM after kernel loaded in the boot process?

I agree that it varies according to the system, like the files related to display manager varies across the system depending on which it supports.

But what are the bare minimal content that are loaded in the RAM from Root File System Hierarchy that must be loaded after kernel loaded?

And also the mount point / is in the hard drive or any solid state device before boot up and after boot up it was loaded into RAM(if I am right) and not all the contents inside / directory are loaded into RAM.

Then my another question is how does any of file accesses or writes or execution (in case of executables) differentiated that some are in RAM and some still not loaded into RAM?In other words how the accessing of specific path is differentiated when some are in RAM and some still not loaded into RAM.

Please reply to my doubt or show me any reference to look for as I could not find by web search.

I do not think anyone can give you an answer. The content of RAM is continuously changing, even the "bare minimum" - which is required to run the OS - is not unconditionally put fully into RAM.

You might want to check how caching works and how process execution works (and what is swap).

I do not understand, it is not loaded (if I understand well).

See again caching and how fork works.

Only bits of running programs are in RAM, not directories and files. The kernel keeps an internal list of inodes of the most recent files and directories that it has accessed. Since top-level directories are being accessed all the time, their inodes will be permanently stored in kernel space, but not their contents.

If you run dmesg through less, it will give you an idea of what the kernel sees & does as it starts up, namely, finds onboard components that require software drivers & loads them, other than that you will need a command shell of some sort.

A bare bones Linux system could consist of a kernel & busybox, just enough to let you do useful things.