Lecture Operating System: Chapter 06 - University of Technology

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Lecture Operating System: Chapter 06 - University of Technology

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Lecture Operating System: Chapter 06 - File Systems presented Files, Directories, File system implementation, Example file systems.

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  1. Chapter 6 File Systems 6.1 Files 6.2 Directories 6.3 File system implementation 6.4 Example file systems
  2. Long-term Information Storage • Must store large amounts of data • Information stored must survive the termination of the process using it • Multiple processes must be able to access the information concurrently
  3. File Naming Typical file extensions.
  4. File Structure • Three kinds of files – byte sequence – record sequence – tree
  5. File Types (a) An executable file (b) An archive
  6. File Access • Sequential access – read all bytes/records from the beginning – cannot jump around, could rewind or back up – convenient when medium was mag tape • Random access – bytes/records read in any order – essential for data base systems – read can be … • move file marker (seek), then read or … • read and then move file marker
  7. File Attributes Possible file attributes
  8. File Operations 1. Create 7. Append 2. Delete 8. Seek 3. Open 9. Get attributes 4. Close 10.Set Attributes 5. Read 11.Rename 6. Write
  9. An Example Program Using File System Calls (1/2)
  10. An Example Program Using File System Calls (2/2)
  11. Memory-Mapped Files (a) Segmented process before mapping files into its address space (b) Process after mapping existing file abc into one segment creating new segment for xyz
  12. Directories Single-Level Directory Systems • A single level directory system – contains 4 files – owned by 3 different people, A, B, and C
  13. Two-level Directory Systems Letters indicate owners of the directories and files
  14. Hierarchical Directory Systems A hierarchical directory system
  15. Path Names A UNIX directory tree
  16. Directory Operations 1. Create 5. Readdir 2. Delete 6. Rename 3. Opendir 7. Link 4. Closedir 8. Unlink
  17. File System Implementation A possible file system layout
  18. Implementing Files (1) (a) Contiguous allocation of disk space for 7 files (b) State of the disk after files D and E have been removed
  19. Implementing Files (2) Storing a file as a linked list of disk blocks
  20. Implementing Files (3) Linked list allocation using a file allocation table in RAM



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