The Linux

1
Chapter 2

• The Linux
• File System

2
Overview

• The purpose and function of files, directories,
  and file systems will be discussed
• Linux ext2 and ext3 native file systems will be
  compared and contrasted

3
Overview

• The hierarchical filing system of a
  tree-structured directory will be explained
• Will learn to read a syntax diagram

4
Overview

• Run the terminal window in GNOME and navigate
  within the terminal window using the absolute and
  relative paths
• Will mount and unmount file systems

5
Overview

• Explain the function of and then use the cal,
  date, pwd, cd, ls, find, history, locate, and
  whereis commands
• The purpose and function of arguments and
  options will be explained and then used

6
Overview

• Will explore file name expansions with those
  commands that support the use of wildcards
  (globbing)
• Determine when redirection should be used and
  then redirect output to a file and a device

7
Understanding the Linux File System

• File
• Named and stored collection of related
  information
• Basic unit of storage

8
Understanding the Linux File System

• Directory
• Way to organize programs/documents
• Hierarchical with system root at the top
• Path
• List of directories Linux follows to
  locate/save/retrieve a file
• Slashes in path act as delimiters

9
Understanding the Linux File System

• File System
• Way any OS names/stores/organizes files on a
  storage device
• Consists of files/directories and information
  needed to locate/access those objects

10
Understanding the Linux File System

• Linux file system ext2 similar to ext3
• Major difference is that ext3 is a journaling
  file system
• Meta data is data about data

11
Understanding the Linux File System

• Foreign file systems that Linux supports
• MSDOS
• UMSDOS
• VFAT
• NTFS
• NFT and SMB

12
Understanding the Linux File System

• Linux file system (ext2 or ext3) is a secure
  operating system

13
Understanding the Linux File System

• Under ext2 or ext3 a file is owned by the person
  who created it
• Categories of file owners
• User
• Group
• Other

14
Understanding the Linux File System

• Types of permissions to be granted
• Read
• Write
• Execute
• Executable programs have additional permissions
• set userid (UID)
• set group userid (GUID)

15
Activity Looking at the File System

• KEY CONCEPTS
• Tree-hierarchical view of computers
  directories
• Hidden files in Linux begin with a dot
• Significance of right/downward pointing arrows
• Use of navigation icons and back/forward buttons
• Function of home, working/current directory
• Parent directorycontains other directories
• Bluecurve theme used with GNOME desktop
• Function of FHS (File System Hierarchy
  Standard)

16
Activity Looking at the File SystemTable 2.1
Common Linux Directories pp. 70-71
17
Activity Looking at the File SystemTable 2.1
Common Linux Directories pp. 70-71
18
Activity Looking at the File SystemTable 2.1
Common Linux Directories pp. 70-71
19
Introducing the Bash Shell

• Shell
• Used to access command line
• Program that interprets keyed in commands
• Buffer between user and OS

20
Introducing the Bash Shell

• Reasons for using the shell
• Interactive use
• Customizing of Linux session
• Programming

21
Introducing the Bash Shell

• Using the shell interactively
• Shell processes and executes commands as they
  are keyed in
• Has built-ins
• Can use a shell script

22
Introducing the Bash Shell

• Once in GNOMEcan access character with a
  terminal emulation program (terminal)
• If GNOME (startx) never starts, then you are at
  command line and in Bash shell

23
Command Syntax

• Syntax is the word order and punctuation of a
  language
• Command syntax is order for keying in computer
  commands

24
Command Syntax

• There are still syntax and rules when using a
  graphical user interface such as GNOME

25
What Are Options and Arguments?

• Option
• Modifies or qualifies a command
• Follows command name separated by a space
• Space is a delimiter
• Begins with a hyphen
• Case sensitive

26
What Are Options and Arguments?

• Argument
• File or directory name
• Follows command options separated by a space

27
What Are Options and Arguments?

• Delimiter
• Character identifies beginning or end of
  character string
• Not part of character string
• In command syntax, space, backslash, forward
  slash are often delimitersdepends on rules of
  command language
• Program interprets character string and knows
  what delimiters are

28
What Are Options and Arguments?

• Can combine options and arguments
• ls -a /bin
• ls -A .
• ls -A . .

29
Reading a Syntax Diagram

• Requirements of command line interface language
• Vocabularycommands
• Grammarpunctuation
• Syntaxorder

30
Reading a Syntax Diagram

• Syntax information provided through online help
• man command name
• commandname --help

31
Reading a Syntax Diagram

• Syntax for Is command
• ls OPTIONS. . .FILE. . .

32
Introducing Commands and the Terminal Window

• To use Linux text commands
• Not have started GNOME
• Opened a terminal window in GNOME
• Know what command to use
• Know allowable options and arguments

33
Activity Looking at the Shell

• KEY CONCEPTS
• How to access terminal window
• Function of profile
• Running terminal window in GNOME is the same as
  running the shell program
• Function and features of the shell
• Function of chsh -1 command
• Examples of popular shells i.e., sh, csh, tsch,
  and ash

34
Activity Looking at the ShellFigure 2.1 Command
Prompt p. 78
35
Navigating in the Shell

• In GNOME, Nautilus is file manager used to locate
  and manage files and directories

36
Activity Navigating the Shell

• KEY CONCEPTS
• Linux prompt shows current current/working
  directory, not entire path
• Compare/contrast absolute/relative path
• Directory only knows its child directories and
  its parent directory
• Functions of pwd, cd, ls, and cal commands
• Use editing keys to alter command line

37
Activity Navigating the ShellTable 2.2 Common
Editing Keys p. 81
38
Activity Navigating the ShellTable 2.2 Common
Editing Keys p. 81
39
Activity Navigating the Shell

• Syntax of the cal command
• cal -mjy13 month year

40
The date and cal commands

• Date and cal commands
• OS keeps track of current date/time
• Date/time indicates system date/time
• System administrator usually maintains/alters
  date/time
• Way system date/time displayed can be altered
• Command is date

41
The date and cal commands

• Cal command
• Displays calendar
• Syntax is cal -mjy13 month year
• No optionsdisplays current month and year

42
The date and cal commandsTable 2.3 cal Options
p. 83
43
Activity Using the date and cal Commands

• Key Concepts
• Display current date
• Display calendar for current month
• Can key in multiple commands on one command line
  if each command is separated by semicolon

44
Mounting File Systems

• File system
• Device formatted to allow the storing and
  retrieval of files
• Organized in a hierarchy

45
Mounting File Systems

• Partitions
• Logical portion of disk
• Part of installation process
• May have its own file system
• Treated by Linux as if they were separate
  physical entities
• Partition labeled /dev/hda3 dedicated to Linux
  swap file

46
Mounting File Systems

• To access files on device (partition or file
  system) must mount device
• In Linux/Unix all files arranged in single tree
  which begins with root directory

47
Mounting File Systems

• In DOS/Windows world devices are mounted
  automatically and process is more transparent
• In Unix/Linux world instead of drive letter,
  device is mounted at a mount point

48
Mounting File SystemsFigure 2.2 The fdisk
Command p.86
49
Mounting File Systems

• Mounting
• Checks a devices status
• Readies it for access
• Mount Point
• Directory in file system that device is mounted
  from
• Hard drivesmounted automatically
• Removable drivesmounted each time used

50
Mounting File Systems

• Mount Point
• Only root user (system administrator) can
  establish mount point
• Once set up root user can allow other users to
  mount/unmount device
• To mount/unmount removable devices root must in
  /etc/fstab file include correct user options

51
Mounting File Systems

• Cannot insert or remove removable media without
  using mount and umount commands.
• Syntax
• mount -t type device mount-point

52
Mounting File Systems

• Any user can mount specified device (/dev/fd0) at
  mount point (/mnt/floppy) by using mount
  /mnt/floppy command if there is a line in fstab
  file that reads
• /dev /fd0 /mnt/floppy auto noauto,owner, kudzu

53
Mounting File Systems

• Syntax for umount command is
• umount dir device

54
Activity Mounting and Unmounting File Systems

• KEY CONCEPTS
• Mount and unmount a device
• Determine what removable devices are mounted
  (options available) or need to be mounted
• Shell scripts are text files and act as
  executable programs
• mtab file lists all file systems currently
  mounted and options they are mounted with

55
Filename Expansions

• To locate a group of files key in abbreviated
  file names containing metacharacters

56
Filename Expansions

• Wildcards (globbing) allow user to operate on a
  group of files rather than a single file
• ?substitutes for a single character
• substitutes for a group or string of
  characters
• allows shell to match individual characters
  within the brackets

57
Filename Expansions

• Ambiguous file references are file names that
  contain special characters i.e., wildcards,
  globbing

58
Activity Filename Expansion

• KEY CONCEPTS
• Determine which version of a program you are
  using in a GUI
• Find utility not available in GUI when using Red
  Hat Linux 9 Nautilus 2.2.1
• Move around window using key strokes and scroll
  bar
• Easier to use command line to locate file(s) or
  directory/directories when exact name not known
• Used , ?, and to locate files/directories

59
The ls Command

• Key in ls
• Lists files and sorts them based on value of the
  characters
• Numbers/Symbols before letters
• Uppercase letter before lowercase letters

60
The ls CommandTable 2.4 Options Used with ls
p.101
Option Name Purpose -1 Lists Lists files
in a single column Note that the option is
the number 1, not the lower case l. -C
Columns Lists files in columns vertically -F
Flags Lists files and directories with
visual clues to items are in a
directory some classify flags include
the following / Directories
Executable files _at_ Symbolic links
61
The ls CommandTable 2.4 Options Used with ls
p.101 - Continued
Option Name Purpose -R Recursive Lists
recursively so that it will list the
directories and files in the subdirectories
of the current directory -S Size Lists
files by size, from largest to the
smallest -X Extension Lists in order by
extension files with no extensions appear
first -a All Lists all the files in the current
or specified directory, including any
hidden files or directories
62
The ls CommandTable 2.4 Options Used with ls
p.101 - Continued
Option Name Purpose -d Directory Lists
directory name, not the names contents
of the directory -k Kilobytes Lists files
sizes in kilobytes Combined with -s option
(-sk) -l Long Provides long format
Includes file details size, date/time,
owner, and permissions -m
Commas Lists file names separated by commas
63
The ls CommandTable 2.54 Options Used with ls
p.101 continued
Option Name Purpose -r Reverse Lists files in
reverse name order When combined with
-t, lists in reverse time order -s Size List
s size of files in blocks -t Time Lists files
by last time created or modified Most recent
files listed first -x Horizontally Lists
files horizontally in rows
64
Activity Using Options with the ls Command

• KEY CONCEPTS
• Use options with the ls command to display files
  in various ways
• Terms recursively, links
• Function of hyphen in a permission slot
• Directories indicated name followed by /
• Files indicated by

65
Activity Using Options with the Is
CommandFigure 2.3 Long Listing p. 103
66
The locate Command

• locate command
• Fastest way to search for file/s in entire
  directory tree
• locate looks in pre-defined database

67
Activity The locate Command

• KEY CONCEPTS
• ltCtrlgt C is quick way to break into command
  and stop it from executing
• Wildcards can be used with locate command
• If database not updated cannot locate files even
  if files are in system

68
The find Command

• find command
• Locates specific file or group of files
• Does not rely on a database
• Searches directory tree for files meeting
  criteria specified
• Searches recursively
• Wildcards can be used in filename statement

69
The find Command

• find syntax
• find pathname -name filename

70
The find CommandTable 2.5 find Options p. 108
71
Activity The find Command

• KEY CONCEPTS
• Directories / follows their name
• Files indicated by
• ls command
• Used to place options after arguments
• Only lists files
• Most commands require options precede arguments
• If path name not specified find only looks in
  default (home) directory

72
Activity The find Command

• KEY CONCEPTS
• Wildcards can be used with find commands
• . (dot) in front of directory/file name
  indicates that it is hidden
• To see hidden directories and files use the -a
  (all) with ls
• If Permission denied appears many times, use
  redirection to filter out these messages

73
Redirection

• Redirection
• Only works with commands that get input from
  standard input device and write to standard
  output device
• Tells OS to write information to file/device
  instead of to screen.
• Works with ls and find commands

74
Redirection

• Redirection Syntax
• command gt destination

75
Redirection

• Can redirect standard error to a device called
  /dev/null
• Example Redirecting error message in find
  command
• find / -iname gedit 2gt/dev/null

76
Activity Redirecting Output to a File and a
Device

• KEY CONCEPTS
• Displayed contents of created file
• Used ls command to redirect output to a file and
  to a null device
• cat command analogous to type command in DOS

77
The whereis Command

• ls, locate, and find commands used to locate
  files of interest
• whereis command locates/displays locations of a
  program, source, and manual pages for a specific
  command

78
The whereis Command

• whereis command
• Determines directory path of programs or their
  source files
• Uses search path to locate list of directories

79
The whereis Command

• whereis command
• Faster than find command since search path is
  built in
• More specific than locate command
• Searching for files that are programs

80
Activity Using the whereis Command

• KEY CONCEPTS
• Most binary programs located in the /usr/bin
  directory
• Most documentation located in /usr/share/man
  directory
• Cannot execute a command unless it is in your
  search path
• Must have permission to execute a command