Chapter Two
Exploring the UNIX/Linux File Systems and File Security
Guide To UNIX Using Linux Fourth EditionChapter 2 Unix (31 slides) 1CTEC 110
• Discuss UNIX/Linux file systems• Explain partitions and inodes• Understand the elements of the root hierarchy• Use the mount command• Explain and use paths, pathnames, and prompts• Navigate the file system• Create and remove directories• Copy and delete files• Configure file permissions
Objectives
Chapter 2 Unix (31 slides) 2CTEC 110
• File: basic component for data storage– UNIX/Linux considers everything to be a file
• A file system is UNIX/Linux’s way of organizing files on mass storage devices– A physical file system is a section of the hard
disk that has been formatted to hold files• The file system is organized in a hierarchical
structure (inverted tree)
Understanding UNIX/LinuxFile Systems
Chapter 2 Unix (31 slides) 3CTEC 110
Understanding UNIX/LinuxFile Systems (continued)
Chapter 2 Unix (31 slides) 4CTEC 110
• The structure starts at the root level– Root is the name of the file at this basic level
and it is denoted by the slash character (/)• Directory: file that can contain other files and
directories• Subdirectory: directory within a directory
– The subdirectory is considered the child of the parent directory
Understanding the Standard Tree Structure
Chapter 2 Unix (31 slides) 5CTEC 110
• The section of the disk that holds a file system is called a partition– When installing UNIX/Linux, one of the first
tasks is deciding how to partition a storage device, or hard disk
– Hard disks may have many partitions• UNIX/Linux partitions are given names
– LINUX uses hda1 and hda2
Using UNIX/Linux Partitions
Chapter 2 Unix (31 slides) 6CTEC 110
• Storage devices are called peripheral devices• Peripheral devices connect to the computer
through electronic interfaces– IDE: Integrated Drive Electronics– SCSI: Small Computer System Interface
Using UNIX/Linux Partitions (continued)
Chapter 2 Unix (31 slides) 7CTEC 110
Chapter 2 Unix (31 slides) 8CTEC 110
• Partitioning your hard disk provides organized space for file systems
• At least 3 partitions (root, swap, /boot) often recommended
• Root partition holds root file system directory (/), size depends on installation but often ranges between 1.2 to 5+ GB
Setting Up Hard Disk Partitions
Chapter 2 Unix (31 slides) 9CTEC 110
• Swap partition acts as a memory extension, often has same size as RAM, enables virtual memory
• /boot partition used to store the os files comprising the kernel and is relatively small
• Other used partitions include /usr, /home, /var
Setting Up Hard Disk Partitions (continued)
Chapter 2 Unix (31 slides) 10CTEC 110
• Inodes are associated with directories and files in ufs and ext file systems
• An inode contains the name, general information, and location information (a pointer) for a file or directory
• A superblock contains information about the block layout on a specific partition
Using Inodes
Chapter 2 Unix (31 slides) 11CTEC 110
• UNIX/Linux must mount a file system before any programs can access files on it
• To mount a file system is to connect it to the directory tree structure
• The root file system is mounted by the kernel when
the system starts
Exploring the Root Hierarchy
Chapter 2 Unix (31 slides) 12CTEC 110
• The root directory contains sub-directories that contain files:– /bin contains binaries, or executables needed to
start the system and perform system tasks– /boot contains files needed by the bootstrap
loader as well as kernel images– /dev contains system device reference files
Exploring the Root Hierarchy (continued)
Chapter 2 Unix (31 slides) 13CTEC 110
Chapter 2 Unix (31 slides) 14CTEC 110
• Root subdirectories continued:– /etc contains configuration files that the system
uses when the computer starts– /lib contains kernel modules, security information,
and the shared library images– /mnt contains mount points for temporary mounts
by the system administrator– /proc is a virtual file system allocated in memory
only
Exploring the Root Hierarchy (continued)
Chapter 2 Unix (31 slides) 15CTEC 110
• Root subdirectories continued:– /root is the home directory of the root user, or the
system administrator– /sbin contains essential network programs used
only by the system administrator – /tmp is a temporary place to store data during
processing cycles– /var contains subdirectories which have sizes that
often change, such as error logs
Exploring the Root Hierarchy (continued)
Chapter 2 Unix (31 slides) 16CTEC 110
• Users can access mounted file systems which they have permission to access
• Additional file systems can be mounted at any time using the mount command
• To ensure system security, only the root user uses
the mount command
Using the mount Command
Chapter 2 Unix (31 slides) 17CTEC 110
• To specify a file or directory, use its pathname, which follows the branches of the file system to the desired file– A forward slash (/) separates each directory
name– The UNIX/Linux command prompt may indicate
your location within the file system– Use the UNIX/Linux pwd command to display
the current path name
Using Paths, Pathnames, and Prompts
Chapter 2 Unix (31 slides) 18CTEC 110
Chapter 2 Unix (31 slides) 19CTEC 110
Chapter 2 Unix (31 slides) 20CTEC 110
• To navigate the UNIX/Linux directory structure, use the cd (change directory) command
• UNIX/Linux refers to a path as either:– Absolute - begins at the root level and lists all
subdirectories to the destination file– Relative - begins at your current working
directory and proceeds from there
Navigating the File System
Chapter 2 Unix (31 slides) 21CTEC 110
• UNIX/Linux interpret a single dot (.) to mean the current working directory
• Two dots (..) mean the parent directory• cd .. moves you up a level in the directory structure
Using Dot and Dot Dot Addressing Techniques
Chapter 2 Unix (31 slides) 22CTEC 110
The ls (list) command displays a directory’s contents, including files and subdirectories
Listing Directory Contents
Chapter 2 Unix (31 slides) 23CTEC 110
• A wildcard is a special character that is used as a placeholder
• The * wildcard represents any group of characters in a file name
• The ? wildcard represents a single character in a file name
Using Wildcards
Chapter 2 Unix (31 slides) 24CTEC 110
• mkdir (make directory) command– Create a new directory
• rmdir (remove directory) command– Delete an empty directory
• cp (copy) command– Copy files from one directory to another
• rm (remove) command– Delete files
Creating and Removing Directories and Files
Chapter 2 Unix (31 slides) 25CTEC 110
Configuring File Permissions for Security
Chapter 2 Unix (31 slides) 26CTEC 110
Configuring File Permissions for Security (continued)
File Permissionsr Owner has read
w Owner has write
x Owner has execute
r Group has read
- Group does not have write
x Group has execute
r Others have read
- Others do not have write
x Others have execute
Chapter 2 Unix (31 slides) 27CTEC 110
• chmod command– To set file permissions– Settings are read (r), write (w), execute (x)– The three types of users are owners(users),
groups, and others(world) or simply (ugo)• Setting permissions to directories
– Use the execute (x) to grant access
Configuring File Permissions for Security (continued)
Chapter 2 Unix (31 slides) 28CTEC 110
• Work through Hands-on Projects at end of chapter 2
• Canvas: Review Questions 2– (Do not do questions 22,23,24 and 25)
• Read chapter 3 before next class session
• Quiz 2 Unix…
Chapter 2 Unix Exercises
Chapter 2 Unix (31 slides) 31CTEC 110
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