A Guide to Unix Using Linux Fourth Edition

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A Guide to Unix Using Linux Fourth Edition

• Chapter 8
• Exploring the UNIX/Linux Utilities

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Objectives

• Understand many of the UNIX/Linux utilities that
  are available and how they are classified
• Use the dd utility to copy and convert files
• Monitor hard disk usage
• Use system status utilities
• Monitor and manage processes
• Check the spelling of text in a document

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Objectives (continued)

• Use the cmp command to compare the contents of
  two files
• Format text to create and use a man page
• Use the dump command to back up a system
• Send and receive e-mail
• Use basic network commands and utilities

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Understanding UNIX/Linux Utilities

• UNIX/Linux utilities are classified into
• File processing
• System status
• Networking
• Communications
• Security
• Programming
• Source code management
• Miscellaneous

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Classifying UNIX/Linux Utilities

• Several categories
• Network tasks
• Programming tasks
• File-processing utilities
• Make up the largest category
• Display and manipulate files

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Classifying UNIX/Linux Utilities (continued)
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Classifying UNIX/Linux Utilities (continued)
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Classifying UNIX/Linux Utilities (continued)
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Classifying UNIX/Linux Utilities (continued)
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Classifying UNIX/Linux Utilities (continued)
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Using the dd Command
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Checking Hard Disk Usage

• Basic strategies used to maintain adequate free
  space
• Be vigilant against running dangerously low on
  free space
• Use df command
• Watch for conspicuous consumption
• Use du command
• Follow a routine schedule for garbage
  collection and removal
• Use a combination of find and rm commands

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Using the df Utility

• If entered without specifying file system, shows
  information for all mounted file systems

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Using the df Utility (continued)
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Using the du Utility

• With no options, report is based on all file
  usage
• Starts at current directory
• By default, output is in number of 512-byte blocks

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Removing Garbage Files

• Garbage files are temporary files that lose their
  usefulness after several days
• Remove to free space
• Example core files, compilation output
• Core file created when executing program
  attempts to do something illegal
• Example accessing another users memory
• Use find and rm to find and remove garbage files
• find . "(" -name a.out -o -name core ")" -exec rm
  \

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Using System Status Utilities

• System status commands reflect systems
  performance
• You can redirect the output of these commands to
  a file
• File can later be
• Printed
• Forwarded to system administrator and system
  tune-up specialists

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Using the top Command
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Using the uptime Command

• Example use it to track how long system has been
  up since last problem requiring a reboot

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Using the free Command

• Swap space is disk space that acts like an
  extension of memory

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Using the free Command (continued)
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Forwarding top and free Output

• You may forward output of top and free to a
  computer support person for analysis
• Example
• top n 3 gt topdata
• lpr topdata

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Managing Processes

• When you run a program, it starts one or more
  processes
• Processes are identified through a unique number
• Process id or PID
• UNIX and Linux offer utilities to
• Manage how a program is run
• Monitor processes
• Kill processes

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Running Processes in the Background

• UNIX/Linux is a multitasking OS
• You can run processes in the background
• To run a process in background
• Append the character
• Example
• top

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Monitoring Processes

• If used with no options, shows a list of
  processes associated with the current login
  session

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Monitoring Processes (continued)
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Killing Processes

• System administrator may want to kill a users
  process because
• Associated program is malfunctioning
• Associated program is using too many system
  resources
• A user may want to kill a process that is running
  in the background

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Checking the Spelling of a Document

• ispell
• Scans a text document
• Displays errors on screen
• Suggests other words with similar spellings as
  replacements for unrecognized words

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Checking the Spelling of a Document (continued)
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Comparing Files

• If the contents are identical, there is no output
• Otherwise, output specifies first byte
  (character) that is different between the files

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Formatting Text in UNIX/Linux
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Archiving and Backing Up Files

• Good practice to periodically archive or back up
  files
• You can back up files to
• CD, DVD, tape, or another removable medium
• For backup to CD/DVD, consider using a GUI tool
• Example GNOME CD/DVD Creator GUI software
• Part of Nautilus

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Using the dump Command
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Using the restore Command

• Restores from a backup medium created via dump
• By default, copies back to current working
  directory
• Example restore -r -f /dev/st0

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Using mail to Send Mail

• Press Ctrld to exit the text mode
• To leave the mail utility, type q and press Enter

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Using mail to Send Mail (continued)
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Using mail to Send Mail (continued)
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Using Networking Utilities

• UNIX and Linux offer many utilities to
  accommodate a connection to the network
• ifconfig
• ping
• traceroute
• netstat

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Using the ifconfig Utility

• Internet Protocol (IP) is used to help ensure
  that information on a network goes to the right
  place
• IP address uses a dotted decimal notation
• Consists of four octets separated by periods
• Identifies a computer/device and the network it
  is on

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Using the ping Utility

• Examples
• ping rbrown_at_xxx.com
• ping redhat.com

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Using the traceroute Utility

• Sample use
• To ensure your computer is connected and working
• To ensure your network is working from point to
  point

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Using the netstat Utility

• Information provided by netstat includes
• Network protocol communications
• Network connections established by host computer
• Network routing information
• Information about remotely logged computers

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Sharing Resources Using Network File System

• Network File System (NFS) used for resource
  sharing over a network
• Once partition is mounted, access is transparent
• mount bluefin/home/mpalmer/shared /mnt/shared
• Three versions typically supported
• NFSv2, NFSv3, and NFSv4
• Client and host communicate via RPCs
• RPC Remote Procedure Call
• Portmap service
• Handles RPC request to mount a partition
• Makes computer act like a server for NFS file
  access

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Sharing Resources Using Network File System
(continued)

• To start a service, use service command
• service portmap
• NFS security handled through entries in
• /etc/hosts.allow, /etc/hosts.deny, and
  /etc/exports

/home/mpalmer/shared 192.168.0.72(ro)
192.168.0.84(ro) /home/mpalmer/docs
192.168.0.72(rw) 192.168.0.41(rw)
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Accessing Microsoft Windows Systems Through Samba

• Samba utility that uses the SMB protocol
• Server Message Block (SMB) is used by Windows
  systems for sharing folders and printers
• Typical configuration file
• /etc/samba/smb.conf file
• Some ways to access Windows shared drives
• Network Servers ? Windows Network
• Computer ? More Applications ? Network Servers
  File Browser ? Windows Network
• K menu ? KNOPPIX ? Utilities ? Samba Network
  Neighborhood

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Summary

• Some useful utility programs are
• dd, df, and du for converting files, checking
  free space, and checking disk usage, respectively
• find and rm can be used together to remove
  garbage files
• top and free provide detailed views of system
  internals
• uptime shows how long a system has been up
• ps and kill to display and kill processes
• ispell to check for spelling errors in a file
• nroff, troff, and groff for formatting output

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Summary (continued)

• Other useful utility programs are
• dump and restore to archive and restore backups
• mail to send and retrieve mail
• ifconfig, ping, traceroute, and netstat for
  viewing information about the network connection
  and for troubleshooting the connection
• Services for sharing resources over network
• Network File System (NFS) to access resources in
  another UNIX/Linux computer
• Samba to access resources in a Windows computer

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Command Summary