Which file in /proc gets read by the kernel during the boot up process?

My question is, which file in /proc gets read by the kernel during the boot up process? This was a question on my LPIC 101 test...

Sounds like a trick question. The files in /proc aren't real files on disk (this is why they have a size of 0) and the nodes don't exist until the kernel mounts a procfs file system there and populates it.

Procfs and sysfs files are kernel interfaces. When you read a file in /proc, you are asking the kernel for information and it will supply it. That information is not stored in that file -- nothing is. When you write to a file in /proc, you are sending the kernel information, but again, the information will not be stored in that file.

This is possible because the kernel is the gatekeeper to file access generally. All file access involves system calls, i.e., they must pass through the kernel.

So I would say the answer here is that it does not read any files in /proc at boot or at any other time. This would be like dialing your own phone number.