The Unix file system is divided into four sequential blocks namely Boot block, Super block, Inode block and the data block as shown below. In all the blocks except data blocks, all are fixed at the time of creation. and data blocks will be changed when the file content is changed.
The Boot Block: This block is starting of the file system and booting code (bootstrapping) will be stored here.Each file system should have one boot block to boot the system. Only one boot block is need to boot the system and if you have more than one file systems, other boot blocks will be empty. So for starting the machine, Operating systems reads the data from boot block to load.
The Super Block: This block specifies the status of the file system. It provides the information like how much space available, how large the file system, total size of the disk, total used blocks, bad blocks etc.
The Inode Block: This blocks specifies the information about the files. each file will have one unique inode (information node) on the disk. The inode contains the information like owner of the file, file type, permissions of the file etc.
The Data Blocks: This block starts immediately after the inode block and this block contains actual data or file content. It also contains other files which contains user data like FIFO, regular files, directory files, character special , block special and socket files etc.
I will post in detail about the Inode structure later.