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Overview: Linux and Unix. (OS comparison). Credit: Cailan Hao (Lancy) Instructor: Mort Anvari Date: 11/3/1999 Southeastern University. The symbol of Linux. SECTION I: LINUX OVERVIEW. Basic Linux Information. Slide 2. FREE (GPL Licensed), based heavily on the POSIX and UNIX API's.

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Overview linux and unix l.jpg

Overview: Linux and Unix

(OS comparison)

Credit: Cailan Hao (Lancy)

Instructor: Mort Anvari

Date: 11/3/1999

Southeastern University

The symbol of Linux


Basic linux information l.jpg

SECTION I: LINUX OVERVIEW

Basic Linux Information

Slide 2

  • FREE (GPL Licensed), based heavily on the POSIX and UNIX API's.

  • Supports both 32 and 64 bit hardware; Provide a stable multi-user Internet ready OS.

Note: The word “Linux” throughout the presentation refers to Red Hat Linux 6.0 – the most popular type of Linux.


Memory management l.jpg

SECTION I: LINUX OVERVIEW

Memory Management

Slide 3

  • Linux uses the Buddy algorithm to effectively allocate and de-allocate blocks of pages. (Left Figure)

  • Linux assumes that there are three levels of page tables.

    (Right Figure)


Cache management l.jpg

SECTION I: LINUX OVERVIEW

Cache Management

Slide 4

  • The role of the Linux page cache is to speed up access to files on disk.

  • When swapping pages out to the swap files, Linux avoids writing pages if it does not have to.


How linux processes l.jpg

Linux is a multiprocessing operating system

Its objective is to have a process running on each CPU in the system at all times -maximize CPU utilization.

Linux supports a number of different executable file formats. EX: ELF and Java

Linux can manage the processes in the system, each process is represented by a task_struct data structure

Some common function areas:

State

Running: ready to run

Waiting: waiting for an event

Stopped: process stopped

Zombie: halted

Scheduling Information: which program most deserve to run

Identifiers: used to control this processes access to the files and devices in the system

Times and Timers: Each clock tick, the kernel updates the amount of time in jiffies that the current process has spent in system and in user mode

SECTION I: LINUX OVERVIEW

How Linux Processes

Slide 5


Linux networking l.jpg

Linux implements the internet protocol address family as a series of connected layers of software:

Linux supports the following socket address families or domains:

UNIX - Unix domain sockets,

INET

TCP/IP protocols

AX25 - Amateur radio X25

IPX - Novell IPX

APPLETALK – AppleTalk DDP

X25 - X25

SECTION I: LINUX OVERVIEW

Linux Networking

Slide 6


Linux pci initialization l.jpg

The PCI initialization code in Linux is broken into series of three logical parts:

PCI Device Driver

searches the PCI system; starting at Bus 0 and locates all PCI devices and bridges in the system; builds a linked list of data

PCI BIOS

provides the services described in bib-pci-bios-specification

PCI Fix-up

tidies up the system specific loose ends of PCI initialization.

SECTION I: LINUX OVERVIEW

Linux PCI Initialization

Slide 7


Unix os structure l.jpg

Unix is a series of layered operating system

User programs interact with the kernel through a set of standard system calls

Unix is a multi-user, multi-tasking operating system

SECTION 2 – UNIX OVERVIEW

Unix OS Structure

Slide 8


Unix file system l.jpg

SECTION 2 – UNIX OVERVIEW series of

Unix File System

Slide 9

  • You start with the root directory, denoted by /, at the top and work down through sub-directories underneath it.


Unix directories structure l.jpg

SECTION 2 – UNIX OVERVIEW series of

Unix Directories Structure

Slide 10

  • Every directory and file is listed in its parent directory.

  • An inode is a special file designed to be read by the kernel to learn the information about each file. – function: specifies the permissions on the file, ownership, date of creation and of last access and change.

  • The system – does not require particular structure for the data in the file itself.

  • There's no header, trailer, label information or EOF character as part of the file.


Unix common control keys l.jpg

SECTION 2 – UNIX OVERVIEW series of

Unix Common Control Keys

Slide 11

  • Control keys - used to perform special functions on the command line or within an editor in Unix

  • ^S, With control keys upper and lower case are the same, so ^S is the same as ^s. This particular example is a stop signal and tells the terminal to stop accepting input

  • EX: Control-U is normally the "line-kill" signal for your terminal. It erases the entire input file.


Unix shell l.jpg

SECTION 2 – UNIX OVERVIEW series of

Unix Shell

Slide 12

  • The shell - acting as a command interpreter - reads your terminal input and translates the commands into actions taken by the system.

  • The shell is analogous to command.com in DOS. The original shell was the Bourne shell, sh. Every Unix platform will either have the Bourne shell, or a Bourne compatible shell available.

  • The default prompt for the Bourne shell is $ (or #, for the root user). The default prompt for the C shell is %.


Similarity file system l.jpg

For both OS: series of

Separate filesystems that the system may use are not accessed by device identifiers (such as a drive number or a drive name) but instead they are combined into a single hierarchical tree structure that represents the filesystem as a single entity.

Unix and Linux transparently supports many different filesystems (for example MS-DOS and EXT2) and presents all of the mounted files and filesystems as one integrated virtual filesystem.

SECTION 3 - COMPARISON

Similarity - File System

Slide 13


Similarity memory management l.jpg

SECTION 3 - COMPARISON series of

Similarity – Memory Management

Slide 14

  • Linux supports the Unix TM System V shared memory IPC.


Similarity ipc l.jpg

SECTION 3 - COMPARISON series of

Similarity - IPC

Slide 15

  • Inter-Process Communication

    • Linux supports the classic Unix TM IPC mechanisms of signals, pipes and semaphores and also the System V IPC mechanisms of shared memory, semaphores and message queues.


Similarity identifiers l.jpg

SECTION 3 - COMPARISON series of

Similarity – Identifiers

Slide 16

  • Linux and Unix - uses user and group identifiers to check for access rights to files and images in the system.

  • All of the files in a Linux system have ownerships and permissions, these permissions describe what access the system's users have to that file or directory.


Similarity executing programs l.jpg

SECTION 3 - COMPARISON series of

Similarity – Executing Programs

Slide 17

  • In both OS - programs and commands are normally executed by a command interpreter. (A command interpreter is a user process like any other process and is called a shell 2)

  • Shells - searches the directories in the process's search path, held in the PATH environment variable, for an executable image with a matching name.


Similarity ext2 file system l.jpg

SECTION 3 - COMPARISON series of

Similarity - EXT2 File System

Slide 18

  • A Linux filename has the same format as all Unix TM filenames have. It is a series of directory names separated by forward slashes (``/'') and ending in the file's name.

  • EX: /home/rusling/.cshrc where /home and /rusling are directory names and the file's name is .cshrc.

  • Like Unix TM systems, Linux does not care about the format of the filename itself; it can be any length and consist of any of the printable characters.


Difference l.jpg

END NOTE: THE MAJOR DIFFERENCE series of

DIFFERENCE

Slide 19

  • Although Linux share a lot of similarities with Unix, It is not Unix.

  • Many people think Linux is a kind of Unix but actually, they do not come from the same source code base.


Presentation info l.jpg

Presentation designer: series of Cailan Hao (Lancy)

Presentation Instructor:

Mort Anvari

Presentation content: Overview Linux and Unix – Comparison

Presentation Slides #: 20

Contact Me

Lannee@zdnetmail.com

Name: Lancy

*OS Comparison Presentation

11/3/1999

Presentation Info