Linux: an operating system for everyone
What is Linux ?
Linux is a freely available UNIX-like operating system originally
developped for Intel-based personal computers.
With millions of users worldwide, it has grown to be
the most popular operating system for software development and servers.
Multi-user, multi-tasking
Using Linux, dozens of people can work on a single computer.
Linux supports true preemptive multi-tasking.
Many processes can run independently on a single processor or even
on a multi-processor architecture.
Each process runs in its own protected area of memory.
Linux uses memory protection so no process can access memory assigned
to another process or to the kernel.
A misbehaving program can therefore not crash the entire system.
Compatible with the POSIX 1003.1 standard
The POSIX 1003.1 standard defines an interface to operating systems.
Linux fully supports this standard.
This means that any program which is written to adhere to the standard
is easily ported to Linux.
High efficiency and stability
One of the best qualities of Linux is its stability and efficiency.
A computer running Linux can remain running for many months or
even years without crashing, freezing or needing a reboot.
During that time, the computer can perform many tasks for many
people; quickly and without using much memory or CPU power.
In fact, a large part of the Internet is serviced by old 486 boxes
running Linux.
Architecture independent
Since its original release, Linux is ported to many other hardware
platforms. It now runs on Intel, MIPS, Alpha, Sparc, PowerPC, M68K
and many others.
A program originally written for an Intel PC will probably compile
and run on a Sparc, a PowerPC or any other architecture.
Includes functionality of UNIX System V and BSD 4.3
Does not require extensive hardware
Large parts of Linux software are developed by students who can not
afford to buy the most powerfull computers. It is probably for this
reason that the opertating system has a modest requirement for
resources. Even an Intel 80386 with 4 Megabytes of RAM is sufficient
to run Linux.
Cost-effective
Secure
History of Linux
- Ken Thompson, Dennis Ritchie and Brian Kernighan - First UNIX at Bell Labs in 1970
- Berkely UNIX - BSD 4.2 in 1982
- Richard M. Stallman - GNU project in 1983
- Andrew Tanenbaum - Minix in 1987
- Linus Torvalds - Linux, first release November 1991
Why use Linux ?
- Provides alternatives in base distribution and in applications
- Competition keeps prices low and quality high
- Low cost in both installation and maintenance
- Supported by professionals. No 'helpdesk that does not help'.
- Fast and efficient response to problems through the internet.
- Commercial support is available from an increasing number of suppliers.
- Open Source: source code is usually available. Stay in control of your data.
- Escape the limitations of proprietary systems
- It is fun to use Linux and to write software on Linux.
Security
- Access is restricted to authorized users only
-
- Only the special administrative user 'root' can access critical
system resources.
- Virsusses essentially do not exist on Linux.
Obtaining Linux
- Download from the internet
- User group, e.g. NLUUG
- Distribution CD from RedHat, Suse, Slackware, ...
- Bookshop, computer shop
- Copy from a friend
Linux Application areas
- Server - file, web, dns, printer, database, ftp, firewall, gateway, mail, news, ...
Networking is only natural in Linux. After all, most network protocols
that are used today were developped on UNIX systems. Without UNIX,
the Internet simply would not exist.
It is therefore not surprising the Linux, being derived from UNIX,
can easily act as a server for any kind of network service you can think of.
- Software development
- Hardware development - device drivers are easy to write
- Internet client - browser, mail, news, ftp (e.g. Netscape)
- Science, research, modelling and engineering
- Embedded systems, process control (RT-Linux)
- Multimedia
- Office workstation - text, spreadsheet, Email
Linux is less suitable for
- Financial administration
- Business and Management
Linux Downsides
- Cryptic command syntax
- Documentation is scattered and not always comprehensive
Linux Cost and Maintenance
- List price: [$ / Fl / EURO / DM / Dr] 0.00
- Upgrades and bug fixes by thousands of programmers
- Downloadable from the internet
- New features are tested by thousands of users
- Installation and support
- Managed distributions - RedHat, Slackware, Suse, Debian, ...
- CD's available from bookstore, computer shop, collegue.
- Illegal copies are impossible.
- Package management - rpm
Kernel
The very heart of Linux is the kernel, a piece of software
that runs the machine and provides system resources to the
application programs.
- Filesystems: ext2, minix, ISO9660, FAT, FAT32, ...
- Dynamic hard disk cache
- Processes - preemptive multi tasking, shared objects
- Symmetrical multi processing
- Device drivers - loadable modules
- Network - full TCP/IP and other protocols
- Paging virtual memory management.
- Complete source code available
Available Applications
Over 6000 application files.
- System administration
- Daemons
- Utilities
X Windows
At the bottom of all graphical interfaces is the X Window system.
This is supplemented by a wide variety of window managers and desktop
environments, such as KDE (the K Desktop environment) or GNOME
(GNU Network Object Model Environment).
These desktops offer all the usual utility applications:
file managers (gmc, xfm), terminal emulators, text editors, caclulators, calendars and lots more.
Internet and communications
- Internet: NTP, NFS, NIS, FTP, SNMP,
- Apache HTTP Web server
- Mail(SMTP, POP, IMAP)and NNTP News servers
- Netscape 4.61
- Mail and News readers
- IRC chat client
- PPP, SLIP, ISDN, voice and Fax
Software development
- GNU C++ compiler and debugger
- Standard libraries, including X11, OpenGL
- Debuggers: xxgdb, DDD, strace, lclint
- Integrated environments: KAI (www.kai.com), Code Crusader (www.cco.caltech.edu/~jafl/jcc),
GNUPro (www.cygnus.com/gnupro), xwpe (www.rpi.edu/~payned/xwpe)
- Java development kit, FreeBuilder
- Yacc, Lex, Awk, Perl, Python
- Other languages: Fortran, Pascal, SQL, PHP, Eiffel, Lisp, Python, Smalltalk, m4, Basic, ...
- User interface design: Tcl/Tk, xforms, Qt, gtk, AXE
- Software management: RCS, CVS
- OMT/UML: www.rational.com
Text & Office
- Text processing: SGML, TeX, troff, PostScript, pdf
- Office suites: Applix, StarOffice, WordPerfect
- Ghostview Postscript and PDF interpreter/viewer
Multimedia
- Audio CD player
- MP3 audio, see www.mp3tech.org
- MPEG Video player
- MusicTeX musical scripting
- Broadcast studio- multichannel audio recording and editing
- Rosegarden MIDI
Databases
- Postgres, Sybase, MySQL, Oracle, Informix
Graphics and design
- tgif, xfig - Technical drawing
- gimp, xpaint, xv, ImageMagic - Image processing
- blender - 3D modelling and animation
Amusements and Games
- Screen savers
- Doom, Quake
- Tetris, minesweeper, cardgames, majhong, xpilot, chess, ...
Security
- Internet firewall
- PGP encryption
- Connectivity to other systems: IPX, AppleTalk, samba, vmware, lilo
Online documentation
Easily extendable (SGML, troff, html)
- Man pages
- GNU info
- /usr/doc
- HOWTOs
- LDP - The Linux Documentation Project
References and links
www.linux.org, nllinux, slashdot, www.freshmeat.net
www.fokus.gmd.de, linuxcentral.com
news: comp.os.linux.*, linux.*
(Uitzoeken)