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Chapter 10. Case Study 1: UNIX and LINUX. 10.1 History of unix 10.2 Overview of unix 10.3 Processes in unix 10.4 Memory management in unix 10.5 Input/output in unix 10.6 The unix file system 10.7 Security in unix . UNIX. User Interface. The layers of a UNIX system.

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case study 1 unix and linux

Chapter 10

Case Study 1: UNIX and LINUX

10.1 History of unix

10.2 Overview of unix

10.3 Processes in unix

10.4 Memory management in unix

10.5 Input/output in unix

10.6 The unix file system

10.7 Security in unix

slide2
UNIX

UserInterface

The layers of a UNIX system.

unix utility programs
UNIX Utility Programs

A few of the more common UNIX utility programs required by POSIX

unix kernel
UNIX Kernel

Approximate structure of generic UNIX kernel

processes in unix
Processes in UNIX

Process creation in UNIX.

posix
POSIX

The signals required by POSIX.

system calls for process management
System Calls for Process Management

s is an error code

pid is a process ID

residual is the remaining time from the previous alarm

posix shell
POSIX Shell

A highly simplified shell

threads in posix
Threads in POSIX

The principal POSIX thread calls.

the ls command
The ls Command

Steps in executing the command ls type to the shell

flags for linux clone
Flags for Linux clone

Bits in the sharing_flags bitmap

unix scheduler
UNIX Scheduler

The UNIX scheduler is based on a multilevel queue structure

booting unix
Booting UNIX

The sequences of processes used to boot some systems

cp

handling memory
Handling Memory

Process A

Process B

  • Process A's virtual address space
  • Physical memory
  • Process B's virtual address space
sharing files
Sharing Files

Two processes can share a mapped file.

A new file mapped simultaneously into two processes

system calls for memory management
System Calls for Memory Management
  • s is an error code
  • b and addr are memory addresses
  • len is a length
  • prot controls protection
  • flags are miscellaneous bits
  • fd is a file descriptor
  • offset is a file offset
paging in unix
Paging in UNIX

The core map in 4BSD.

The core map has an entry for each page

paging in linux 1
Paging in Linux (1)

Linux uses three-level page tables

paging in linux 2
Paging in Linux (2)

Operation of the buddy algorithm.

Buddy algorithm

networking
Networking

Use of sockets for networking

terminal management
Terminal Management

The main POSIX calls for managing the terminal

unix i o 1
UNIX I/O (1)

Some of the fields of a typical cdevsw table

unix i o 2
UNIX I/O (2)

The UNIX I/O system in BSD

streams
Streams

An example of streams in System V

the unix file system 1
The UNIX File System (1)

Some important directories found in most UNIX systems

the unix file system 2
The UNIX File System (2)
  • Before linking.
  • After linking.

(a) Before linking. (b) After linking

the unix file system 3
The UNIX File System (3)
  • Separate file systems
  • After mounting

(a)

(b)

(a) Before mounting. (b) After mounting

locking files
Locking Files

(a) File with one lock

(b) Addition of a second lock

(c) A third lock

system calls for file management
System Calls for File Management
  • s is an error code
  • fd is a file descriptor
  • position is a file offset
the lstat system call
The lstat System Call

Fields returned by the lstat system call.

system calls for directory management
System Calls for Directory Management
  • s is an error code
  • dir identifies a directory stream
  • dirent is a directory entry
unix file system 1
UNIX File System (1)

Disk layout in classical UNIX systems

unix file system 2
UNIX File System (2)

Directory entry fields.

Structure of the i-node

unix file system 3
UNIX File System (3)

The relation between the file descriptor table, the open file description

unix file system 4
UNIX File System (4)
  • A BSD directory with three files
  • The same directory after the file voluminous has been removed
the linux file system
The Linux File System

Layout of the Linux Ex2 file system.

network file system 1
Network File System (1)
  • Examples of remote mounted file systems
  • Directories are shown as squares, files as circles
network file system 2
Network File System (2)

The NFS layer structure.

The NFS layer structure

security in unix
Security in UNIX

Some examples of file protection modes

system calls for file protection
System Calls for File Protection
  • s is an error code
  • uid and gid are the UID and GID, respectively