Managing filesystem types

The s5 superblock

Much of the information about the filesystem is stored in the superblock, including:

filesystem size and status
- label (filesystem name)
- size in logical blocks
- read-only flag
- superblock modified flag
- date and time of last update
inodes
- total number of inodes allocated
- number of free inodes
- array of 100 free inode numbers
- an index into the array of free inode numbers
storage blocks
- total number of free blocks
- array of 50 free block numbers
- an index into the array of free block numbers

NOTE: The superblock does not maintain complete lists of free inodes and free blocks, but only enough to meet current demands as the filesystem is used. At almost any time, unless the filesystem is close to running out of inodes and storage blocks, there are sure to be more free inodes and free blocks than are listed in the superblock.