20.1 The ‘Super Block’ (5561)

The “super block” is always recorded as block #l on the storage device. (Block #0 is always ignored and is available for miscellaneous uses not necessarily concerned with UNIX.)

The “super block” contains information used in allocating resources, viz. the storage blocks and the entries in the “inode” table recorded on the file system. While the file system volume is mounted a copy of the “super block” is maintained in core and updated there. To prevent the storage device copy becoming too far out of date, its contents are written out at regular intervals.