operating-systems distributed-systems
Definition
Distributed System
A distributed system is a collection of independent computers that appears to its users as a single coherent system.
Operating System Types
Network Operating System
Definition
Link to originalNetwork Operating System
A network operating system (NOS) is a system where users are aware of multiple computers. Each machine runs its own local OS and provides tools for remote access (
ssh,ftp, shared network drives).
- Control: Highly decentralised
- Transparency: Low
Distributed Operating System
Definition
Link to originalDistributed Operating System
A distributed operating system (DOS) manages resources across multiple machines as a single system. Users do not know which physical machine executes their process or stores their data.
- Control: Centralised logical view
- Transparency: High
File System Transparency
Location Transparency
The file name does not reveal its physical location. However, moving the file may require a name change (e.g.,
\\server1\file.txt).
Location Independence
The file name is completely independent of its physical location. A file can be moved without changing its name or how applications access it.
Mutual Exclusion
Centralised
A single coordinator manages all critical section requests.
Token-based
A logical token circulates the network; only the holder enters the critical section.
Decentralised (Voting)
A process must obtain permission from a majority of nodes before entering.