operating-systems file-management
Definition
File System Layout
The file system layout describes the physical organisation of data on a disk partition. It ensures that the OS can locate the root directory and manage allocated vs. free blocks.
Disk Structure
A physical disk is typically divided into one or more partitions, each containing an independent file system.
Master Boot Record (MBR)
Located in Sector 0 of the disk. It contains:
- Boot Code: Executed by the BIOS during system start.
- Partition Table: Stores the start/end addresses of all partitions and identifies the active partition.
Partition Layout
A typical Unix/Linux partition layout includes:
- Boot Block: Used to load the OS kernel from this partition.
- Super Block: Contains critical metadata about the file system (e.g., size, block count, magic number, and pointers to other structures).
- Free Space Management: Tracks unallocated blocks (e.g., via a bit table).
- i-node Table: Contains an array of i-nodes, one for each potential file.
- Root Directory: The top of the file hierarchy.
- Files & Directories: The actual user data blocks.