Which file contains the boot related information in Linux?

Answer 1

There's no single file that contains the boot information. Nor is the method of booting uniform across all platforms and distributions. There are dozens of bootloaders, each of which have their own configuration files in various locations.

Answer 2

There is no specific set or list of files that need to exist to boot a Linux system. Once the kernel launches the init program, the rest of the boot process depends entirely on the style of that init. There are several different init styles, hence different file names and locations. Furthermore, the boot process will also vary depending on what daemons the system will be running and are launched by init.