Network Guide to Networks, Fourth Edition

1
Network Guide to Networks, Fourth Edition

• Chapter 9
• Networking with UNIX-Type of Operating Systems

2
A Brief History of UNIX

• UNIX led to development of TCP/IP
• Numerous vendors sell different UNIX varieties
• Ken Thompson and Dennis Ritchie developed UNIX at
  Bell Labs (part of ATT)
• System V
• UNIX source code was cheaply available from ATT
• Quickly distributed to many organizations

3
A Brief History of UNIX (continued)

• Berkeley Software Distribution (BSD) Berkeley
  versions of UNIX
• Added TCP/IP network subsystem to UNIX
• ATT sold rights to UNIX
• Now owned by two groups
• The SCO Group owns rights to UNIX source code
• The Open Group owns UNIX trademark

4
Varieties of UNIX

• All flavors of UNIX share the following features
• Support multiple, simultaneously logged-on users
• Coordinate multiple, simultaneously running tasks
• Mount disk partitions on demand
• Apply permissions for file and directory access
  and modification
• Uniform method of issuing data to or receiving
  data from hardware devices, files, and running
  programs
• Start programs without interfering running
  programs

5
Varieties of UNIX (continued)

• All flavors of UNIX share the following features
  (continued)
• Hundreds of subsystems, including dozens of
  programming languages
• Source code portability
• Window interfaces (e.g., X Windows)
• Two main categories
• Proprietary
• Open source

6
Proprietary UNIX

• Source code either unavailable or available only
  by purchasing licensed copy from the SCO Group
• Mac OS X Server Apple
• Runs on PowerPC-based computers
• Solaris Sun
• Runs on SPARC-based workstations and servers,
  Intel-based Pentium-class workstations and
  servers
• AIX IBM
• Runs on PowerPC-based computers
• Does not run on Macs

7
Proprietary UNIX (continued)

• Advantages
• Accountability and support
• Optimization of hardware and software
• Predictability and compatibility
• Customer has no access to systems source code
• Cannot customize

8
Open Source UNIX

• Open source software available to anyone, without
  licensing fees
• Open source UNIX flavors
• GNU
• BSD
• Linux
• Users can modify code
• Add functionality
• Can be installed on wide range of systems

9
Three Flavors of UNIX

• Solaris used by Sun Microsystems on its
  SPARC-based servers
• Linux follows standard UNIX conventions, highly
  stable, and free
• Developed by Linus Torvalds in 1991
• Widely supported and used
• Mac OS X Server Runs on Apples Xserve line of
  computers as well as Power Mac computers
• All support TCP/IP and other protocols
• Support many network topologies and physical media

10
UNIX Server Hardware Requirements

• Any UNIX-type OS can act as a workstation or
  server OS
• Use of GUI optional
• Command line interface
• To estimate additional hardware required
• Server usage?
• Applications and services to be run on server?
• Number of users?
• Peak usage time periods?
• Maximum tolerable downtime?

11
A Closer Look at UNIX UNIX Multiprocessing

• Allocate separate resources (e.g., memory space)
  to each process as it is created
• Enables partitioning of processes in memory
• Prevent programs from disrupting operation of
  entire system
• Support symmetric multiprocessing (SMP)
• Solaris up to 128 processors
• Linux up to 32 processors
• Mac OS X Server up to 2 processors

12
The UNIX Memory Model

• Use both physical and virtual memory efficiently
• Allocate memory area for each application
• Sharing memory between programs wherever possible
• Increases efficiency
• Most use 32-bit addressing scheme
• Enables programs to access 4 GB of memory
• Most can run on CPUs employing 64-bit addresses
• Virtual memory disk partition or a file

13
The UNIX Kernel

• Core of all UNIX-type of systems
• Loaded into memory and runs computer turned on
• Coordinates access to computers hardware
• Can add or remove functionality by loading and
  unloading kernel modules
• Files containing instructions for performing
  specific tasks
• Kernel origins
• Solaris original ATT UNIX software
• Linux Linus Torvalds
• Mac OS X Server (XNU) Mach

14
UNIX System File Services

• Disk File Systems
• OSs facility for organizing, managing, and
  accessing files through logical structures and
  software routines
• Native file system type on Linux is ext3
• Solaris employs UFS
• Mac OS X Server employs HFS file system
• Can access FAT and NTFS partitions

15
UNIX System File Services (continued)

• Network File Systems (NFSs) analogous to Windows
  shares or NetWare network volumes
• Attach shared file systems (or drives) from
  Windows, NetWare, or other UNIX servers and share
  files with users on other computers
• Sun Microsystems NFS
• Samba open source application that implements
  Windows SMB and CIFS file system protocols
• Included with Solaris, most Linux distributions,
  and Mac OS X Server systems by default
• Mac OS X Server uses AFP

16
A UNIX Command Sampler (continued)
Table 9-4 Commonly used UNIX commands
17
A UNIX Command Sampler (continued)
Table 9-4 (continued) Commonly used UNIX commands
18
A UNIX Command Sampler (continued)
Table 9-4 (continued) Commonly used UNIX commands
19
A UNIX Command Sampler (continued)

• Most frequently used UNIX command is ls
• For each file, system stores all information
  (except filename) in a file information node
  (i-node)
• Beginning of disk partitions contain reserved
  space for all i-nodes on partition
• Contain pointers to actual file contents
• Pipe () combine commands
• Output of one command is input to next
• Pipeline two or more commands connected by a pipe

20
A UNIX Command Sampler (continued)
Figure 9-3 Anatomy of ls l output
21
Administering a UNIX-type of Server

• User names and passwords used to connect clients
  to network
• Access rights for groups
• Users may be members of multiple groups
• groupadd command enables addition of new group
• useradd command enables addition of new users
• Mac OS X Server uses GUI Workgroup Manager
  application

22
Establishing Groups and Users on Linux and Solaris

• groupadd command creates new group ID and makes
  group available for use
• Assign unique ID number to each group
• Does not automatically assign access rights
• useradd command adds new user ID
• Creates user ID and assigns it to one or more
  groups
• -g option specifies initial group
• -G option specifies additional groups

23
Establishing Groups and User on Mac OS X Server

• Use Workgroup Manager application
• Creating new group does not assign users
• Assign unique name and numeric ID to groups

24
Establishing Groups and User on Mac OS X Server
(continued)
Figure 9-4 User creation in Mac OS X Servers
Workgroup Manager
25
Changing File Access Permissions

• Every file and directory is owned by exactly one
  user and is a member of exactly one group
• By default, when a user creates a file or
  directory, that user is the file or directorys
  owner

26
Changing File Access Permissions on Linux and
Solaris

• Use chgrp command to assign a file or directory
  to a group
• Use chmod command to change file and directory
  permissions
• Uses two sets of abbreviations to specify
  permission changes for files
• First set identifies for whom change will occur
  files owner (u for user), files group (g),
  all others (o)
• Second set identifies access rights read (r),
  write (w), and execute (x)
• Separated by plus or minus sign

27
Changing File Access Permissions on Mac OS X
Server

• Accomplished through the GUI
• Must be logged on as system administrator

28
Summary

• UNIX is a stable, flexible, and efficient NOS
  that relies on TCP/IP and forms the basis of much
  of the Internet
• Many varieties of UNIX-type of systems exist, and
  each of these belong to one of two categories
  proprietary and open source
• Characteristics of UNIX-type of systems include
  the ability to support multiple, simultaneous
  users hierarchical files a uniform method for
  interacting with files, devices, and programs
  hundreds of subsystems and dozens of programming
  languages and source code portability

29
Summary (continued)

• UNIX-type of systems use virtual memory and also
  allocate a memory area for each application
• The UNIX kernel, the core of the OS, is loaded
  into memory from disk and runs when you turn on
  your computer
• UNIX-type of systems were among the first to
  include a hierarchical file system
• UNIX-type of systems support multiple file system
  types
• UNIX-type of network file systems include NFS and
  Samba

30
Summary (continued)

• Consult the commands manual (man) page by typing
  man command at the shell prompt, and pressing
  Enter to learn more about a command
• ls command is most frequently used command
• The useradd and groupadd commands allow you to
  add new users and groups
• The chgrp and chmod commands assign files to
  groups and change file access permissions

31
Summary (continued)

• Installing the Samba application on a UNIX-type
  of server allows it to exchange information with
  Windows servers by using Windows file system and
  file access protocols
• All modern flavors of UNIX, Linux, and Mac OS X
  Server support data sharing using directory
  services based on LDAP
• Any client that runs the TCP/IP protocol can
  connect to a UNIX-type of host, such as a Linux
  server, through the Telnet utility