Networking with UNIX and Linux Chapter Nine

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Networking with UNIX and LinuxChapter Nine
2
Brief History of UNIX

• UNIX system is characterized by a rich tradition
  and a culture of personal friendships in an era
  of impersonal disconnectedness that, some would
  say, the computer itself has fostered
• System V
• Versions of UNIX that come from Bell Labs
• BSD (Berkeley Software Division)
• Versions of UNIX from researchers at the
  University of California at Berkeley
• 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

3
Common UNIX Features

• The ability to support multiple, simultaneously
  logged in users
• Hierarchical file systems that incorporate
  demountable volumes
• Consistent interfaces for file, device and
  interprocess input/output
• The ability to start processes in the background
• 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

4
Common UNIX Features

• Hundreds of subsystems, including dozens of
  programming languages
• Program source code portability
• User-definable window system, the most popular of
  which is the X Window system
• Two main categories
• Proprietary
• Open source

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Current State of the Market

• Unix market is huge and highly segmented
• Some real-time implementations of the UNIX system
  exist
• Operating system must respond to input immediately

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Proprietary UNIX

• An implementation of UNIX for which the source
  code is either unavailable or available only by
  purchasing a licensed copy from The Santa Cruz
  Operation
• Suns proprietary version of UNIX is called
  Solaris
• Runs on SPARC-based workstations and servers,
  Intel-based Pentium-class workstations and
  servers
• IBMs proprietary version of UNIX is called AIX
• Runs on PowerPC-based computers
• Does not run on Macs
• Novells proprietary version of UNIX is called
  SUSE
• Apple Mac OS X
• Runs on Xserve server
• Runs on PowerPC-based computers

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Choosing a Proprietary UNIX System

• Advantages
• Accountability and support
• Optimization of hardware and software
• Predictability and compatibility
• Drawback
• Customer has no access to the systems source
  code and thus cannot create a custom solution

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Open Source Softwareand Open Source UNIX

• Software developed and packaged by a few
  individuals and made available to anyone without
  licensing fees
• Also called freely distributable software
• Includes UNIX-like systems such as Linux, GNU,
  FreeBSD, Ubuntu, SlackWare, Mandrake, and RedHat
• Flavor
• Different implementations of UNIX-like systems

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Selecting a Network Operating System

• Is it compatible with existing infrastructure?
• Will it provide the security required by the
  networks resources?
• Can the technical staff manage it effectively?
• Will existing applications run smoothly on it?

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Selecting a Network Operating System

• Will existing applications run smoothly on it
• Will it accommodate future growth (that is, is it
  scalable)?
• Does it support additional services the networks
  users require?
• How much does it cost?
• What type of sort can be expected from the vendor?

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Choosing UNIX

• Samba
• Open source software package
• Complete Windows NT-style file and print sharing
  facility
• UNIX was originally developed as a time-sharing
  system
• Computing system to which each user must attach
  directly to share the resources of that computer
• Some proprietary UNIX systems have received
  Orange Book certification
• Rigorous operating system security specification
  first published by U.S. Department of Defense in
  1985

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Hardware for a UNIX Server

• Basic system unit must include
• Motherboard with CPU, memory, and I/O control
• Network interface card (NIC)
• Floppy disk drive
• CD-ROM drive
• One or more fixed disks

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Decisions in Choosing Hardware

• Which applications and services will run on the
  server?
• How many users will this system serve?
• How much random access memory (RAM) will the
  server need?
• How much secondary storage (hard disk) will the
  server need?

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Hardware

• More current lists of supported hardware on the
  hardware compatibility list (HCL) at
  http//metalab.unc.edu/LDP/HOWTO/Hardware-HOWTO.ht
  ml

Minimum requirements for a Linux RedHat server
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Minimum hardware requirements for Solaris 10
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Mac OS X Server Hardware Requirements
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Preinstallation Questions

• What is the new servers name?
• What is the servers IP address?
• What kind of video card is installed in the
  server?
• What kind of monitor is attached to the new
  server?
• What is the administrative users password?
• How can I remember all this information?

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Pre-installation Requirements

• A clean PC that satisfies the Linux hardware
  requirements
• The distribution media for Red Hat version
  (CD-ROM and floppy disk)
• One or two hours of uninterrupted time
• Read more about multiboot systems at the Linux
  installation HOWTO site
• http//www.linuxhq.com/LDP/HOWTO/Installation-HOWT
  O.html

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A Closer Look at Linux

• Linux multiprocessing
• Supports symmetric multiprocessing (SMP)
• Linux memory model
• From its inception, Linux was created to use both
  physical and virtual memory efficiently

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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

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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

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Layered View of Linux Operating System
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Linux

• Kernel
• Controls computer system resources
• Scheduling user jobs
• Ensure a fair use of system resources
• As in NetWare, is the core of the system
• Also similar to NetWare, it is possible to add or
  remove functionality by loading and unloading
  Linux kernel modules
• Analogous to NetWare NLMs

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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

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Linux

• Shell
• Command line and initiates execution of commands
• X Window System
• Graphical User Interface
• Motif(mwm)
• The standard window manager
• fvwm - f Virtual Window Manager
• Allows greater customization

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Client/Server

• Server
• Managers the display
• Client communicates with Server
• Client
• Running program

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Linux Command Sampler

• Command interpreter
• Program that accepts your typing and runs the
  command
• Also known as a shell
• Keeps track of the command history, much like the
  doskey command in DOS and Windows NT

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Shell - xterm
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Linux File and Directory Structure

• Hierarchical file system
• Organization of files and directories on a disk
  partition in which directories may contain files
  and directories

Linux file system hierarchy
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UNIX System File and Directory Structure

• First OSs to implement hierarchical file system
• /boot directory contains kernel and other system
  initialization files
• Applications and services stored in /bin and
  /sbin directories
• /var directory holds variable data
• Users login directories typically in /home
• /Users on Mac OS X Server

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Linux File Services

• Linux includes support for multiple types of file
  systems
• Local file systems
• Remote file systems
• Its native file system, called ext3
• Allows you to access DOS FAT as well as NTFS
• Can both attach shared file systems and share
  local partitions with other users
• Windows or NetWare
• Network File System (NFS)

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Linux File Services

• 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

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Linux 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

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File System

• A file is a sequence of bytes the kernel does
  not impose a structure on files.
• Files are organized in tree-structured
  directories.
• Directories are files that contain information on
  how to find other files.

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File System

• Path name identifies a file by specifying a path
  through the directory structure to the file.
• Absolute path names start at root of file system,
  e.g., /home/rtracy/phone/calls
• Relative path names start at the current
  directory, e.g., phone/calls

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File System

• Directories
• Used to organize the hierarchical file system
• Directories are just files with a special format,
  so the representation of a file is the basic UNIX
  concept.
• Ordinary Files
• Plain text or binary files (executable file)
• Special Files
• Special files such as lp for a line printer
  /dev/lp

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Disk Organization

• Disks are divided into 512 bytes block
• Four regions
• reserved for booting
• size of disk and boundaries
• file definitions, device numbers, i-numbers to
  uniquely identify files
• free blocks

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i-node or File Descriptor

• Owners ID
• Physical address
• Protection Bits (r,w,x)
• File Size
• Time of creation, last update, and last use
• File Type (d - for directory)
• Links

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i-node
Memos
Name i-number
notes
Calculate
I-node for notes I-node for Calculate
File Info
File Info
0 block pointer
0 block pointer
1 block pointer
1 block pointer
2 block pointer
2 block pointer
Block 0
Block 1
Block 0
Block 1
Block 2
notes
notes
Calculate
Calculate
Calculate
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File Hierarchy

• Root Directory
• /
• Parent Proceeded by /
• cd Change Directory
• cd .. Up one level
• cd home directory

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Long Listing ls -l

• drwxrwxr-x
• User, group, entire system
• d indicates directory
• r read
• w write
• x execute
• - no acess

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System Utilities

• Used by the system administrator to monitor the
  state of the system.
• Taskbar - displays taskbar on desktop
• Memory Usage, system load, active processes - top
• Identify Window - display information about a
  window
• size, location, title

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Linux Command Sampler

• Manual pages
• Linux system documentation for all commands
• Section 1 covers commands typically entered while
  typing in a command window
• Sections 2 through 7 document the programmers
  interface to the UNIX system
• Section 8 covers the commands used by
  administrators to manage the system

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Linux Command Sampler

• You can access manual pages by entering the man
  command in a Linux command window
• For example, to read the manual page entry for
  the telnet command, enter man telnet in a command
  window

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Linux Command Sampler

• To instruct the system to print all files in the
  current directory that have been accessed in the
  past five days, type find . type f atime 5
  print
• To list a file named account.xls, type ls
  account.xls
• Globbing
• Form of filename substitution
• For example, type ls 1 a would produce a
  detailed listing of all files with the letter a

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Linux Command Sampler

• Windows NT separator is character is \
  (backslash)
• The Linux directory separator is / (forward
  slash)
• In a Windows NT command window, the telnet is
  typed as \winnt\system32\telnet.exe
• The telnet command in Linux is /usr/bin/telnet

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Linux Command Sampler

• Pipe (entered as a vertical bar )
• Serves as the connection between two commands
• Pipeline
• Two or more commands separated by a pipe

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Linux Command Sampler
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Linux Command Sampler
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Linux Command Sampler
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Linux Command Sampler

• Linux systems keep quite a bit of information
  about each file, including
• Filename
• File size (in bytes)
• Date and time a files i-node (file information
  node) was created
• Date and time that the file was last accessed
• Date and time that the file contents were last
  modified

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Linux Command Sampler

• Information Linux system keeps about each file
  (cont.)
• Number of aliases or links to the file
• Numeric identifier of the user who owns the file
• Numeric identifier of the group to which the file
  belongs
• Access rights for the owner, the group and all
  others

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Linux Command Sampler

• To learn about the i-node information, use the ls
  command

Example of output from ls
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Linux Command Sampler

• Other valid file types
• l for symbolic link files
• b for block devices
• c for character device files

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Linux Command Sampler
Anatomy of ls output
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Configuring Linux for Network Administration

• Adding groups and users
• Groupadd
• Command to add a new group ID to a Linux system
• Useradd
• Command to add a new user ID to a Linux system

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Configuring Linux for Network Administration

• To add group IDs to a Linux system
• Log in to system as user root
• Type groupadd instructors, then press Enter at
  the command prompt to add group instructors
• Type groupadd students, then press Enter to add
  the group students
• Type groupadd administrators, then press Enter to
  add the group administrators

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Configuring Linux for Network Administration

• To add a new user and assign the user a password
• Type useradd g users G instructors thomas, then
  press Enter to add new user account thomas
• Type passwd thomas, then press Enter
• Type the password and press Enter

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Changing File Access Permissions

• To create a directory and assign it to a group
• To log off Linux, type exit, then press Enter
• To log back on to as thomas, enter thomas at the
  login prompt
• Enter password for thomas
• To create new directory, type the command mkdir
  PROGRAMS, then press Enter
• List the file with ls l
• Enter the command chgrp instructors PROGRAMS to
  assign PROGRAMS to the group instructors

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Changing File Access Permissions

• To change the access permissions for the PROGRAMS
  directory
• Type chmod gw PROGRAMS to add write access for
  the instructors group to PROGRAMS, then press
  Enter
• Type chmod o-rw PROGRAMS to remove read and write
  access by others to PROGRAMS, the press Enter
• Type ls l to view the access permission assigned
  to PROGRAMS

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Installing Red Hat Version of Linux

• Insert the Boot Diskette disk
• Turn on the computer
• Press Enter
• Press Enter after being prompted for basic
  installation information

Welcome to Red Hat Linux screen
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Installing Red Hat Version of Linux

• Press Enter to select your language
• Press the down arrow until us is highlighted,
  then press Enter to select it
• Choose No to PCMCIA support by repeatedly
  pressing the tab key until Linux setup highlights
  No, then press Enter
• Press Enter to choose Local CD-ROM for the medium
  from which youll perform the installation
• When Installation Path screen appears, choose
  Install, then press Enter

63
Installing Red Hat Version of Linux

• Select the type of system being installed by
  choosing Server, then press the arrow key until
  Setup highlights the word Server, then press
  Enter
• Press Enter to indicate your system does not have
  any SCSI devices
• If the Probe Result screen appears once package
  installation is complete, press Enter so Mouse
  Configuration screen appears
• Press Tab once to highlight the Emulate 3 Buttons
  field, then press spacebar to select that option
• You can change mouse configuration with
  /usr/sbin/mouseconfig after the systems up and
  running

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Installing Red Hat Version of Linux

• Press Tab and then press Enter
• When Xconfigurator asks if you want to probe for
  your video card, use Tab to indicate you want
  Setup to probe for your video card, then press
  Enter
• When completing the video hardware configuration
  screens, you can return to previous screens using
  the Back function, then press Tab until the word
  Back is selected and press Enter
• After specifying monitor type, press Tab and then
  Enter
• Press Enter to test the driver

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Installing Red Hat Version of Linux

• You can use the Back function (by pressing Tab
  until Linux setup highlights the Back box, then
  pressing Enter) to return to previous screens and
  select a different video card or monitor if the
  video test pattern looks wrong or doesnt appear
• To configure your server to start with a static
  IP address, press Enter
• On the Configure TCP/IP screen, press Tab to move
  between fields, and press Enter to accept the
  values and continue with TCP/IP configuration

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Installing Red Hat Version of Linux
Configure TCP/IP screen
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Installing Red Hat Version of Linux

• As the Configure Network screen appears, press
  Tab to move between fields and press Enter to
  accept the values and complete the servers
  TCP/IP configuration

Configure Network screen
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Installing Red Hat Version of Linux

• For configuring time zones, press Tab until Linux
  setup highlights Hardware clock set to GMT, press
  Tab and then Enter to accept your choices
• At Root Password screen, enter the password
  twice, then press Tab, and then Enter
• Following prompts, create the Linux Emergency
  Boot Disk
• After final screen appears, press Enter to
  restart server
• Log in to the new Linux server as user root when
  the system presents you with the login prompt

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Internetworking with Other Network Operating
Systems

• UNIX-type of systems and Windows can both
  communicate via TCP/IP
• File systems not necessarily compatible
• Samba one application that bridges file system
  incompatibility
• Provides networking services necessary to make a
  UNIX-type system a fully featured Windows file-
  and printer-sharing server
• Communicates with Windows servers using SMB
  file-sharing protocol and CIFS protocol

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Internetworking with Other Network Operating
Systems

• Samba
• Communicates with Windows servers
• WINE
• Enables Windows programs to run on Linux
• VMware
• Emulates a complete Intel-based computer
• Telnet unsecured terminal emulation
• SSH encrypted secure shell
• Dozens and dozens of command-line utilities that
  enable access to contents of files generated on
  other systems

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Internetworking with Other Network Operating
Systems

• All modern flavors of UNIX, Linux, and Mac OS X
  Server support data sharing using directory
  services based on LDAP
• Solaris Sun Java System Directory Server
  Enterprise Edition
• Linux OpenLDAP
• Mac OS X Server Open Directory

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Linux Internet Servicesand Linux Processes

• Apache
• Open source software application that is the
  leading Internet Web server
• Mail
• SMTP and POP3/IMAP support
• Linux Processes
• Another UNIX innovation is the notion of
  separate, numbered processes