portable operating system proved to be the key to
the success of UNIX. During the 1970s, UNIX evolved through the
development work of programmers at Bell Labs and several
universities, notably the University of California, at
Berkeley. - When UNIX first started to be marketed commercially
in the 1980s, it was used to run powerful network servers, not
desktop computers. Today, there are dozens of different
versions of UNIX, including the following: - Hewlett
Packard UNIX (HP-UX)
- Berkeley Software Design, Inc.
(BSD UNIX), which has produced derivatives such as
FreeBSD
- Santa Cruz Operation (SCO) UNIX
- Sun
Solaris
- IBM UNIX (AIX)
UNIX, in its
various forms, continues to advance its position as the
reliable, secure OS of choice for mission-critical applications
that are crucial to the operation of a business or other
organization. UNIX is also tightly integrated with TCP/IP.
TCP/IP basically grew out of UNIX because of the need for LAN
and WAN communications. The Sun Microsystems Solaris Operating
Environment and its core OS, SunOS, is a high-performance,
versatile, 64-bit implementation of UNIX. Solaris runs on a
wide variety of computers, from Intel-based personal computers
to powerful mainframes and supercomputers. Solaris is currently
the most widely used version of UNIX in the world for large
networks and Internet websites. Sun is also the developer of
the "Write Once, Run Anywhere" Java technology.
Despite the popularity of Microsoft Windows on corporate LANs,
much of the Internet runs on powerful UNIX systems. Although
UNIX is usually associated with expensive hardware and is no
user friendly, recent developments, including the creation of
Linux, have changed that image. Origins of Linux
In
1991, a Finnish student named Linus Torvalds began work on an
operating system for an Intel 80386-based computer. Torvalds
became frustrated with the state of desktop operating systems,
such as DOS, and the expense and licensing issues associated
with commercial UNIX. Torvalds set out to develop an operating
system that was UNIX-like in its operation but used software
code that was open and completely free of charge to all users.
Torvald's work led to a world-wide collaborative effort to
develop Linux, an open source operating system that looks and
feels like UNIX. By the late 1990s, Linux had become a viable
alternative to UNIX on servers and Windows on the desktop. The
popularity of Linux on desktop PCs has also contributed to
interest in using UNIX distributions, such as FreeBSD and Sun
Solaris on the desktop. Versions of Linux can now run on almost
any 32-bit processor, including the Intel 80386, Motorola
68000, Alpha, and PowerPC chips. As with UNIX, there are
numerous versions of Linux. Some are free downloads from the
web, and others are commercially distributed. The following are
a few of the most popular versions of Linux: - Red Hat
Linux – distributed by Red Hat Software
- OpenLinux –
distributed by Caldera
- Corel Linux
- Slackware
- Debian GNU/Linux
- SuSE Linux
Linux is one of the most powerful and reliable
operating systems in the world today. Because of this, Linux
has already made inroads as a platform for power users and in
the enterprise server arena. Linux is less often deployed as a
corporate desktop operating system. Although graphical user
interfaces (GUIs) are available to make Linux user-friendly,
most beginning users find Linux more difficult to use than Mac
OS or Windows. Currently, many companies, such as Red Hat,
SuSE, Corel, and Caldera, are striving to make Linux a viable
operating system for the desktop. - Application support must be
considered when Linux is implemented on a desktop system. The
number of business productivity applications is limited when
compared to Windows. However, some vendors provide Windows
emulation software, such as WABI and WINE, which enables many
Windows applications to run on Linux. Additionally, companies
such as Corel are making Linux versions of their office suites
and other popular software packages. Networking with
Linux
Recent distributions of Linux have networking
components built in for connecting to a LAN, establishing a
dialup connection to the Internet, or other remote network. In
fact, TCP/IP is integrated into the Linux kernel instead of
being implemented as a separate subsystem. Some advantages of
Linux as a desktop operating system and network client include
the following: - It is a true 32-bit operating system.
- It supports preemptive multitasking and virtual
memory.
- The code is open source and thus available
for anyone to enhance and improve.
Content
6.1 Workstations and Servers 6.1.7
Apple Apple Macintosh computers were designed for easy
networking in a peer-to-peer, workgroup situation. Network
interfaces are included as part of the hardware and networking
components are built into the Macintosh operating system.
Ethernet and Token Ring network adapters are available for the
Macintosh. The Macintosh, or Mac, is popular in many
educational institutions and corporate graphics departments.
Macs can be connected to one another in workgroups and can
access AppleShare file servers. Macs can also be connected to
PC LANs that include Microsoft, NetWare, or UNIX servers.
Mac OS X (10)
The Macintosh operating system, Mac OS
X, is sometimes referred to as Apple System 10. Some of the
features of Mac OS X are in the GUI called Aqua. The Aqua GUI
resembles a cross between Microsoft Windows XP and Linux
X-windows GUI. Mac OS X is designed to provide features for the
home computer, such as Internet browsing, video and photo
editing, and games, while still providing features that offer
powerful and customizable tools that IT professionals need in
an operating system. The Mac OS X is fully compatible with
older versions of the Mac operating systems. Mac OS X provides
a new feature that allows for AppleTalk and Windows
connectivity. The Mac OS X core operating system is called
Darwin. Darwin is a UNIX-based, powerful system that provides
stability and performance. These enhancements provide Mac OS X
with support for protected memory, preemptive multitasking,
advanced memory management, and symmetric multiprocessing. This
makes Mac OS X a formidable competitor amongst operating
systems.
Content 6.1 Workstations and
Servers 6.1.8 Concept of service on servers
Networking operating systems (NOSs) are designed to provide
network processes to clients. Network services include the
World Wide Web (WWW), file sharing, mail exchange, directory
services, remote management, and print services. Remote
management is a powerful service that allows administrators to
configure networked systems that are miles apart. It is
important to understand that these network processes are
referred to as services in Windows 2000 and daemons in UNIX and
Linux. Network processes all provide the same functions, but
the way processes are loaded and interact with the NOS are
different in each operating system. Depending on the NOS, some
of these key network processes may be enabled during a default
installation. Most popular network processes rely on the TCP/IP
suite of protocols. Because TCP/IP is an open, well-known set
of protocols, TCP/IP-based services are vulnerable to
unauthorized scans and malicious attacks. Denial of service
(DoS) attacks, computer viruses, and fast-spreading Internet
worms have forced NOS designers to reconsider which network
services are started automatically. Recent versions of popular
NOSs, such as Windows 2000 and Red Hat Linux 7, restrict the
number of network services that are on by default. When
deploying a NOS, key network services will need to be enabled
manually. When a user decides to print in a networked printing
environment, the job is sent to the appropriate queue for the
selected printer. Print queues stack the incoming print jobs
and services them using a first-in, first-out (FIFO) order.
When a job is added to the queue, it is placed at the end of