Transcript Chapter One - Bucks County Community College

Chapter Two
Exploring the UNIX File
System and File Security
Lesson A
Understanding Files and Directories
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Objectives
Discuss and explain the UNIX file system
Define a UNIX file system partition
Use the mount command to mount a file
system
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Objectives (cont.)
Discuss relative and absolute path
addressing
Diagram the UNIX file system hierarchy
Navigate the file system
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Understanding the UNIX
File System
A file is the basic component for data storage
– UNIX considers everything it interacts with a file
A file system is UNIX’s way of organizing files on
mass storage (disk) 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 similar to an inverted tree
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Understanding the Standard
Tree Structure
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 (/)
A directory is a file that can contain other files
and directories
A subdirectory is a directory within a directory
– The subdirectory is considered the child of the parent
directory
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Using UNIX Partitions
The section of the disk that holds a file
system is called a partition
– When installing UNIX, one of the first tasks is
deciding how to partition a storage device, or hard
disk
– Hard disks may have many partitions
UNIX partitions are given names
– LINUX uses hda1 and hda2
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Using UNIX Partitions
Storage devices are called peripheral
devices
Peripheral devices connect to the
computer through electronic interfaces
– IDE - Integrated Drive Electronics
– SCSI - Small Computer System Interface
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Exploring the Root File System
UNIX 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
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Exploring the Root File
System
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
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Exploring the Root File
System
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
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Exploring the Root File
System
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
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Using the Mount
Command
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
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Understanding Paths
and Pathnames
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 command prompt may indicate
your location within the file system
– Use the UNIX pwd command to display the
current path name
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Navigating the File System
To navigate the UNIX directory structure,
use the cd (change directory) command
UNIX 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
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Listing Directory Contents
The ls (list)
command displays
a directory’s
contents, including
files and
subdirectories
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Listing Directory Contents
The system
normally uses
hidden files to keep
configuration
information and for
other purposes
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Lesson B
Working with Files, Directories, and
Security
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Objectives
Create new directories to store files
Copy files from one directory to
another
Set file permissions for other user
access to directory and files
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Managing Directories and
Files
mkdir (make directory) command
– Create a new directory
rmdir (make directory) command
– Delete an empty directory
cp (copy) command
– Copy files from one director to another
rm (remove) command
– Delete files
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Setting File Permissions
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Setting File Permissions
File Permissions
r
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
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Setting File Permissions
for Security
chmod command
– To set file permissions
– Settings are read (r), write (w), execute (x)
– The three types of users are owners, groups,
and others
Setting permissions to directories
– Use the execute (x) to grant access
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Chapter Summary
In UNIX, a file is the basic component for data
storage and UNIX considers everything a file
A file system is the UNIX system’s way of
organizing files on mass storage devices and
each file is referenced using a correct and
unique pathname
The standard tree structure starts with the root
(/) directory
The section of the mass storage device (or
disk) that holds a file system is a partition
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Chapter Summary
A path serves as as a map to access any file
on the system
You may customize your command prompt to
display the current working directory name, the
current date and time, and several other items
The ls command displays the names of files
and directories contained in a directory
Wildcard characters (i.e. *, ?) can be used in a
command such as ls and take the place of
other characters in a file name
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Chapter Summary
Use the mkdir command to create a new
directory, as long as you own the parent
Use the chmod command to set
permissions such as read (r), write (w),
execute (x) for files that you own
Use the cp command to copy a source
file to a destination file and directory
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