Bash Scripts Basic

7/28/2019 Bash Scripts Basic

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1.1

The Unix System

Unix is a Multi-user and Multi-tasking operating

system History

MULTICS (MULTIplexed Information and ComputingService) (1965)

Ken Thompson (Bell Laboratories -1969)Space Wars, PDP-7, written in ASSEMBLER

UNICS (UNiplexed Information and Computing Service)

Ken Thompson, Dennis Ritchie (1970-1974)

UNIX, PDP-11

Ritchie develops C language (starting from B language)

The third version of UNIX is written in C

A paper on UNIX is published in 1974 (ACM TuringAward 1984)


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1.2

The Unix System

History,Bell Labs and AT&T UNIX PDP-11 is the computer of many departments of computer

science and so UNIX becomes the OS of the Universities

Bell Labs and AT&T UNIX development groups develop severalversion of UNIX:

first edition (1969), ,seventh edition (1978,on PDP-11/70)

a version for Interdata 8/2 and VAX UNIX for a network of computers

System III (1982 - first commercial version)

System V based on System III(1983)

System V release 2, 3, 4 (1984 - 1989)

SVR4 (System V release 4; 1989 AT&T and Sun Microsystems)

1993: AT&T becomes a phone company and sells UNIX toNovell


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1.3

The Unix System History University of California at Berkeley

The most influential of the non-Bell Labs and non-AT&T

UNIX development groups:.Thompson and some students develop 1BSD (Berkeley

Software Distributions) starting from sixth edition (the first oneout of Bell Labs) (1978).

3BSD - 4BSD UNIX resulted from DARPA funding to develop

a standard UNIX system for government use.This series contains 4.1BSD, 4.2BSD, 4.3BSD and 4.4BSD

(1980-93) and has some important new tools: virtual memory,paging, multiuser, network connection by means of TCP/IP.

4.2BSD contains the text editorvi, the shell csh, Pascal and

Lisp compilers,

Sun Microsystem, DEC and some other companiesdecides to develop their UNIX version starting from BSDversions instead of System V.


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1.4

History of

UNIX Versions


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1.5

The Standardization Projects

History

Several standardization projects seek to consolidate thevariant flavors of UNIX leading to one programming

interface to UNIX. The most important are:

POSIX (Portable Operating System): merge of System V

and BSD (1984)

IBM, DEC, Hewlett-Packard create OSF (Open Software

Foundation) and their UNIX system is OSF/1 (1988)

X/OPEN defines the Single UNIX specification (1993) and

the systems satisfying this specification have the trademark

UNIX 95Open group (merge of Open Software Foundation and

X/OPEN; http://www.opengroup.com 1996)

Definition of the second version of the Single UNIX

specification (1997) with the trademark UNIX 98
http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/http://www.opengroup.com/


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1.6

A variant of the UNIX System

Although there are many version of UNIX, themost important companies provide versionbased on UNIX System V Release 4 (SVR4) andthe last the Single UNIX specification ex. Solaris 2.x is the most widely used and most

successful commercial UNIX implementation.

These systems are very big and verycomplicated (the contrary of the Thompsonsbasic idea) and in same case expensive.

So, Tanenbaum develops MINIX (1987) a smallfree UNIX system (11800 rows of C code and800 rows of Assembler code) satisfying POSIX.MINIX is a free educational system based on micro-

kernel model (www.cs.vu.nl/~ast/minix.html)
http://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.htmlhttp://www.cs.vu.nl/~ast/minix.html


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1.7

Common System Components of an OS

Process Management

Main Memory Management

File Management

Secondary Memory Management

I/O System Management

Networking

Protection System

Command-Interpreter System (Shell)


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1.8

System Structure

System structure: defines the connectionsand manages the System Components

Some system structuresa. Monolithic

b. Client-Server model (micro-kernel)


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1.9

Monolithic Operating System Structure

A monolithic system has not a well defined structure. Itincludes virtually all of the operating-system functionalityin one large block of code that runs as a single processwith a single address space. All the functionalcomponents of the kernel have access to all of its internaldata structures and routines.


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1.10

The Client-Server Model

Moves as much from the kernel into user

space. In this way it remains only a micro-kernel.

Communication takes place between user

modules using message passing.


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1.11

The Client-Server Model

Advantages

easier to extend a micro-kernel

easier to port the operating system to new architectures

more reliable (less code is running in kernel mode)

more secure

Disadvantages

Deterioration of the performances

MINIX has the I/O drivers into the kernel (this is for

technical reasons connected to 8088 architecture), while

the Main Memory Management, and the File

Management are two different user processes.


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1.12

The Linux System

There is not a free BSD system at the end of the

eighties, and so many members of MINIXnewsgroup ask to Tanenbaum to introduce many

modifications for improving the performances of

MINIX. Some of these modifications could

change the original educational project ofTanenbaum, and so often he said NO to these

requests.

So, Linus Torvalds using a pc 386 with MINIXdevelops a small but self-contained kernel in

1991 (Linux 0.01), with the major design goal of

UNIX compatibility (i.e., satisfying POSIX).


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1.13

Linux 0.01

The first version of Linux (Linux 0.01) has some of

features of MINIX (ex. File system), but the maindifferences between Linux and MINIX are: The Linux kernel uses a monolithic model, and it has

many more functions than the micro-kernel of MINIX.

From a theoretical point of view MINIX is better thanLinux, but from a practical point of view theperformances of Linux are better than that one ofMINIX.

However, for a description of the point of view of

Torvalds on the advantages-disadvantages of Linux-MINIX see the flame war between Torvalds andTanenbaum in:

Rivoluzionario per caso: come ho creato Linux (solo perdivertirmi), Linus Torvalds, Garzanti


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1.14

The Linux Kernel

Linux 0.01 (May 1991) had no networking, ran only on80386-compatible Intel processors and on PC hardware,

had extremely limited device-drive support, and supportedonly the Minix file system.

Linux 1.0 (March 1994) included these new features: Support forUNIXs standard TCP/IP networking protocols

BSD-compatible socket interface for networking programming

Device-driver support for running IP over an Ethernet

Enhanced file system

Support for a range of SCSI controllers for high-performance diskaccess

Extra hardware support

This version is sufficient compatible with UNIX and manypeople are interested in developing Linux under Torvaldsupervision.

Linux 1.2 (March 1995) was the final PC-only Linux kernel.


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1.15

Linux 2.0 Released in June 1996, 2.0 added two major new

capabilities:

Support for multiple architectures Support for multiprocessor architectures

Other new features included: Improved memory-management code

Improved TCP/IP performance

Support for internal kernel threads, for handling dependenciesbetween loadable modules, and for automatic loading of modules ondemand.

Standardized configuration interface

Available for Motorola 68000-series processors, Sun Sparc

systems, and for PC and PowerMac systems. Linux 2.2 January 1999 improves some aspects of Linux 2.0

The last release is Linux 2.4.20 (production) Linux 2.5.64(development)
http://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.5/64/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.htmlhttp://www.linuxhq.com/kernel/v2.4/20/index.html


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1.16

The Moral of the Story

Linux is a modern, free operating system based on UNIXstandards.

First developed as a small but self-contained kernel in1991 by Linus Torvalds, with the major design goal ofUNIX compatibility.

Its history has been one of collaboration by many users

from all around the world, corresponding almostexclusively over the Internet (software open source).

It has been designed to run efficiently and reliably oncommon PC hardware, but also runs on a variety of otherplatforms.

The core Linux operating system kernel is entirelyoriginal, but it can run much existing free UNIX software,resulting in an entire UNIX-compatible operating systemfree from proprietary code.


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1.17

The Linux System

Linux uses many tools developed as part ofBerkeleys BSD

operating system, System V, MITs X Window System, andthe Free Software Foundation's GNU project.

The main system libraries were started by the GNU (GNUs

Not Unix) project (ex. gcc (GNU C compiler)), with

improvements provided by the Linux community. Linux networking-administration tools were derived from 4.3

BSD code; recent BSD derivatives such as FreeBSD have

borrowed code from Linux in return.

The Linux system is maintained by a network of developerscollaborating on Internet (see /usr/src/linux/CREDITS), with

a small number of public ftp sites acting as de facto

standard repositories.
http://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htmhttp://localhost/var/www/apps/conversion/tmp/scratch_4/gnu/Panoramica%20del%20Progetto%20GNU%20-%20Free%20Software%20Foundation%20(FSF).htm


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1.18

Linux Distributions

Standard, precompiled sets of packages, or distributions,

include the basic Linux system, system installation andmanagement utilities, and ready-to-install packages of

common UNIX tools.

The first distributions managed these packages by simply

providing a means of unpacking all the files into theappropriate places; modern distributions include advanced

package management.

Red Hat, Debian, SuSE, Mandrake are popular

distributions from commercial and noncommercial sources,

respectively (see www.linux.org).

The RPM Package file format permits compatibility among

the various Linux distributions (see www.linuxbase.org).
http://www.linux.org/http://www.linuxbase.org/http://www.linuxbase.org/http://www.linuxbase.org/http://www.linuxbase.org/http://www.linuxbase.org/http://www.linuxbase.org/http://www.linux.org/http://www.linux.org/http://www.linux.org/http://www.linux.org/http://www.linux.org/


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1.19

Which distribution to use ?

RedHat (www.redhat.com)

Big, professional, very widely used

Debian (www.debian.org/)

Open development model, excellent packaging

system

Mandrake (www.mandrakesoft.com)

Aims to be very easy to install and use

SuSE (www.suse.com/)

Compromise between Red Hat and Mandrake

Slackware (www.slackware.com/)

Most traditional; little extra help
http://www.redhat.com/http://www.debian.org/http://www.mandrakesoft.com/http://www.suse.com/http://www.slackware.com/http://www.slackware.com/http://www.slackware.com/http://www.slackware.com/http://www.slackware.com/http://www.slackware.com/http://www.suse.com/http://www.suse.com/http://www.suse.com/http://www.suse.com/http://www.suse.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.debian.org/http://www.debian.org/http://www.debian.org/http://www.debian.org/http://www.debian.org/http://www.redhat.com/http://www.redhat.com/http://www.redhat.com/http://www.redhat.com/http://www.redhat.com/


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1.20

Mandrake Distribution

Mandrake provides a simple and friendly

distribution. Maybe, it is the best distribution for thedesktop (www.mandrakesoft.com).

The last release of Mandrake distribution isMandrake 9.0 Dolphin and it is contained in three

CDs. It contains the Linux kernel 2.4.19. The minimum installation requires only the first

CD and takes only 60MB. The other two CDcontain many packages.

There are two different GUI (Graphical UserInterface): KDE (release 3.0.3) and GNOME (2.0.1)
http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/http://www.mandrakesoft.com/


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1.21

Mandrake Installation

The installation of Mandrake 9.0 Dolphin is very easy. You can select Italian language

The first time you should choose the installation forprincipiante

The more difficult step is the partition of the hard disk. Apartition correspond to a logic disk. If you want to installsome operating systems on your hard disk, you have to define

a partition for each OS. A disk has at most 4 primarypartitions. You can make these partitions by means of thecommand fdisk.The Mandrake installation provides asimple graphical tool for making the Linux partitions.

We wish to point out that from DOS/Windows you cannot see

the other partitions. On the contrary, Linux see DOS/Windowspartition (/mnt/windows).

However, all the steps of the installation will beillustrated during the lecture.


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1.22

The Moral of the Installation

Varies from distribution to distribution

Most modern distributions make it easy: Buy CD / download and burn CD image

Boot

Follow instructions

Need to think about partitioning.

Install a boot loader (probably LILO (LInux

LOader), maybe something else). This needs tobe configured to boot whatever other operatingsystems you have installed.


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1.23

Users Linux is an intrinsically multi-user system

Every user on the system has its own username

and password The root user has ultimate power to run the

system. You should not log in as rootunlessyou really need to.

During installation, you should have beenprompted for a root password and also ausername and password for an ordinary useraccount.

The commandpasswd allows to change thepassword.

Careful: you have to perform the programshutdown h now before to switch off the PC


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1.24

Linux Licensing

The Linux kernel is distributed under the GNU

General Public License (GPL), the terms of whichare set out by the Free Software Foundation. See /usr/src/linux/COPYING

The main consequence of GPL is that anyoneusing Linux, or creating their own derivative ofLinux, may not make the derived productproprietary; software released under the GPL may

not be redistributed as a binary-only product.

For a deeper examination of this subject seewww.gnu.org/home.it.html
http://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.htmlhttp://www.gnu.org/home.it.html

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