Unix System Kernel

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Unix System Kernel
Unix: Introduction
Operating System: a system that manages the resources
of a computer.
Resources: CPUs, Memory, I/O devices, Network
Kernel: the memory resident portion of Unix system
File system and process control system are two major
components of Unix Kernel.
Architecture of Unix System
OS interacts directly with
the hardware
Such OS is called
system kernel
Unix System Kernel
Three major tasks of kernel:
Process Management
Device Management
File Management
Three additional Services for Kernel:
Virtual Memory
Networking
Network File Systems
Experimental Kernel Features:
Multiprocessor support
Lightweight process (thread) support
Block Diagram of System Kernel
Process Control Subsystem
Process Synchronization
Interprocess communication
Memory management:
Scheduler: process scheduling
(allocate CPU to Processes
File subsystem
Hardware Control
Processes
Processes
User mode and Kernel mode
Process Table
User Table (u area)

Shared Program Text and Software Libraries

System Call
System call: fork()

System Call: getpid() getppid()

System Call: wait()

System Call: exec()

Handling Signal
Handling Signal

Scheduling Processes
Process Priority
Process Scheduling (Unix System V)

Booting
The first processes
init process

File Subsystem
File System Layout
Boot Block
Superblock
I-nodes

I-node structure
Data Block

In-core inode table
In-core inode table
File table
User File Descriptor table
System Call: open

System Call: read

System Call: dup

System Call: creat
System Call: close
System Call: write

System Call: stat/fstat

System Call: link/unlink
System Call: chdir