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Introduction to UNIX /
Linux
Dr. Jerry Shiao, Silicon Valley University
Summer 2015
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Course Description
 Overview of Operating Systems.

UNIX/Linux Software Architecture.

UNIX Shells (Bourne, C, BASH).
Editor (vi, emacs) and Electronic Mail.
Files and File System Structure.
File Security.
Advanced File Processing.
File Sharing.
Redirection and Piping.
Process and Job Control.
Networking and Internetworking.
Bourne Shell Programming.
C Shell Progamming.
File System Backup.
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Hands-On Lab

Redhat Linux Host Development System.
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Course Description

Class Evaluation.



30 %: Midterm. First half material.
30 %: Final. Second half material.
30 %: Homework.

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10 %: Attendance. Participtation.
Lab Evaluation.


No late Homework.
12 Lab Assignments.
References:
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UNIX, The Textbook 2nd Edition, Syed Mansoor Sarwar
A Practical Guide to Linux, Mark G. Sobell
http://class.svuca.edu/~sau/class/CS206/
 Homework Assignments.
 Lab Assignments.
 Lecture Slide.
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Course Description

Lab Assignments

Assignment 1:
 Quick Start Into UNIX.
 Overview of OS.
Assignment 2:
 UNIX Software Architecture.
 UNIX Shell.
Assignment 3:
 UNIX Editors.
 Editing Text Files.
Assignment 4:
 UNIX File System.
 UNIX File Security.
Assignment 5:
 Basic File Processing.
 Advanced File Processing.
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Course Description
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Assignment 6:
 File Sharing.
 File Redirection and Piping.
Assignment 7:
 Processes.
 UNIX Networking and Internetworking.
Assignment 8:
 Bourne Shell Programming.
 Advanced Bourne Shell Programming.
Assignment 9:
 C Shell Programming.
 Advanced C Shell Programming.
Assignment 10:
 File System Backup.
Assignment 11:
 UNIX Tools.
Assignment 12:
 UNIX GUI Basics.
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Course Description

http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html
Binaries
The latest release version (beta 0.63). This will generally be a version I
think is reasonably likely to work well. If you have a problem with the
release version, it might be worth trying out the latest development
snapshot (below) to see if I've already fixed the bug, before
reporting it to me.
For Windows on Intel x86
PuTTY:
putty.exe
(or by FTP) (RSA sig) (DSA sig)
...

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Course Description
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Course Description

MAC OS X:
In the “Applications/Utilities” folder, open “Terminal”.
In the upper-right corner of
the MAC main window,
there is also a “Search”
area. Type in “Terminal”.

ssh <User Name>@<Server IP Address>
ssh [email protected]
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Introduction UNIX/Linux Course Outline
 Section 1 UNIX/Linux Introduction







QuickStart into UNIX Operating System
 UNIX User Interface: Predominant interaction is text-based.
 Connect and Log On to UNIX Operating System.
 Maintain and Organize Files.
 Online Help for UNIX Commands.
 Common Utility Commands.
UNIX At the Beginning
 Overview of Operating Systems.
 Computer Systems Software.
 UNIX Family History.
UNIX Software Architecture
 UNIX Kernel and Device Driver.
 UNIX System Call Interface and Library.
UNIX or Linux?
File Maintenance Commands
Utility Commands
Aliases
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Section 1 UNIX/Linux Introduction
 Computer System:


What is an Operating System? Primary purpose is to faciliate:


Easy, Efficient, Fair, Orderly and Secure use of hardware and
software resources through Application Software (MSWord, Excel).
Bottom-Up Operating System View:



Consists of hardware and software resources.
Software that allocates and de-allocates system resources
(Resource Manager) in an efficient, fair, orderly, and secure
manner.
Memory allocated to process, Printer accesses one file, CPU
scheduled between processes.
Top-Down Operating System View:

Software isolates users from hardware resources.




User does not know physical location of file on disk, structure and size
of the disk, and number or name of the drive on the system.
Application Programmer’s Interface ( API ): System Calls
Abstraction layer (Virtual File System) allows common interface to
hardware resources.
Simple User Interfaces (CLI).
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Section 1 UNIX/Linux Introduction
 Layered View of a Computer System
Application programs
(word processors,
spreadsheets, games,
graphing tools, picture
processing tools, Web
browsers)
Unix Shell, File Operation
Commands
Keyboard, Display
Screen, RAM, disk drive,
modem, CPU.
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Section 1 UNIX/Linux Introduction
 Operating System Services


Services allow execution of user and system application
efficiently and securely.
Services designed to execute software (Application Programs):


Input and Output operations performed by programs:


System Logs
Manipulation of all types of files


Linux Message Queues, Semaphores, Shared Memory
Error Detection and Reporting


Hides details of underlying I/O hardware: stdin, stdout, stderr, pipe
Communication between processes same/different computer


Provides environment: Memory allocation, multi-processing,
scheduling
Secondary Storage Management: cp, mv,rm, mkdir
Management of users and security


Login Access Control, Password Management Control
Security-Enhanced Linux (SELinux) Access Control Policy
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Section 1 UNIX/Linux Introduction
 Character Versus Graphic User Interface
 Using Computer System require user to provide
commands to the Operating System.
 Character User Interface (CUI)

Keyboard issue command to the Operating System.



DOS, UNIX
UNIX primary input device.
Maximum flexibility: Run commands directly: Minimal layer
between user and system process.
 Graphical User Interface (GUI)
 Mouse (point-and-click device) issue command to the
Operating System.



MacOS, Microsoft Windows
UNIX runs X Window System based GUI (RunLevel 5).
Minimal flexibility: Extra layer Graphical process between
user and the system process, causing delay in execution.
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Section 1 UNIX/Linux Introduction
 Types of Operating Systems

Single-User, Single-Process System




Single-User, Multiprocess System






Multiple user use simultaneously and each user can run multiple processes.
CPU resource multiplexed – process performing I/O while another process
use CPU.
Time-Sharing System: Scheduler context switches between concurrently
executing processes, appear to be single user.
UNIX, LINUX, WindowsNT Server, MVS, VM/CMS.
Interactive Operating System


One user at a time and user runs multiple processes simultaneously.
OS/2, Windows XP Workstations.
Multiuser, Multiprocess System


One user at a time and user runs only one process at a time.
CPU resource left idle while process performing I/O.
MacOS, DOS, Windows 3.1.
UNIX, LINUX, DOS, Windows, etc.
Batch Operating System

VMS running payroll programs.
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Section 1 UNIX/Linux Introduction
 Summary

Operating System manage system’s hardware and software
resources.





Services provided include: Program Execution, I/O Operations,
communication between processes, error detection and reporting,
and file manipulation.
Operating System categorized: Single-User Single-Process,
Single-User Multi-processes, and Multi-User Multi-Processes.
Multiuser and Multiprocess are Time-Sharing Systems: Increase
utilitzation of system resources by switching them among
concurrently executing processes.
Character User Interface; Command entered directly to
Operating System.
Graphical User Interface: Command entered through point-andclick device.
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Section 1 UNIX/Linux Introduction
 Evolution of Linux:
 Developed in Response to need of heterogenous
Community of Computer Uses.

Open Software System:




Evolution Shaped by a Populist Mindset.
UNIX/Linux Community


Diverse Audience
MULTICS: 1965 Multiuser Operating System


Source Code FREELY Distributed among Community of Users.
Not Dominated by a Corporation of Institution Entity: Contributions
by different User Groups and broad range of topics.
Complexity in Software and Hardware to support multiple users.
UNIX: 1969 Bell Laboratories early Inception as
Laboratory Research Tool …
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Section 1 UNIX/Linux Introduction
AT&T
Bell Labs: Ken Thompson and Dennis Ritchie
C Source Code
Multi-User, Multi-processor.
Bell Labs
Bourne Shell
1969
Microsoft created
Xenix from UNIX
System V.
BSD
Version
1-6
1980
System III
Xenix
C Shell
Microsoft teams
with IBM OS/2 and
transferred
ownership to Santa
Cruz Operations
(SCO).
1 BSD
4 BSD
Korn Shell
SUN OS
System V
1990
UNIXware
Linux
System V and BSD
Open Source
2000
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SCO UNIX
Novell
SCO
acquires
UNIXware
Solaris
Solaris 2
POSIX
Portable Operating System Interface
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4.4 BSD
FreeBSD
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Section 1 UNIX/Linux Introduction
 UNIX Operating System Development in Bell
Laboratories

UNIX System developed and written in C language, small
subset tailored to target processor.


Releases distributed in C Source Code:


UNIX did NOT follow other Operating System development:
Most Operating System programs written in an assembly
language, specifically tailored to the architecture of the
processor.
Easily modified and improved upon to add functionality by
users of Operating System.
Multiple processes able to execute concurrently and
connected through streams.
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Section 1 UNIX/Linux Introduction


Computer System Hardware and Software Components
(Resources)
Computer System Hardware


Several Subsystems: Main/Primary Memory, CPU(s), Secondary
Storage (Flash, Hard Disk Drives) and Input/Output Devices
(CDROM, Keyboard, Scanner, Printer, and Mouse).
Main/Primary Storage


Storage location addressed by Byte.
Store executing processes and data currently in use.



Kernel space separated from user space.
Volatile storage, loses content when powered off.
Central Processing Unit (CPU)

Control Unit



Executes programs by fetching instructions from the RAM. Each
processor has its own instruction set.
Interacts with device controllers ( memory, keyboard, disk, monitor).
Arithmetic and Logic Unit (ALU) executes instruction fetched by the
Control Unit.
Registers used as temporary storage locations.

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Section 1 UNIX/Linux Introduction
 Computer System Hardware


Disk (Desktop) or Flash (Embedded Systems)
 Highest Latency in Computer System (Head Seek Time).
 Contains all of the Computer System’s programs and
applications (Kernel, user applications).
 Nonvolatile storage, retains content when powered off.
Bus
 Parallel wiring carry information from one subsystem to
another.
 System Bus:




Data Bus – carry data from one subsystem to another (i.e. program
code from main memory to CPU).
Address Bus – Address of main memory location to read/write.
Control Bus – Control Information (i.e. read/write from CPU to main
memory).
I/O Devices
 Allows user to run commands and apps, supply inputs,
capture outputs (i.e. keyboard, mouse, monitor, printer).
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Section 1 UNIX/Linux Introduction
 Computer

System Hardware
Machine Cycle – CPU / System Bus
CPU Control Unit:
1) Fetches program
instruction.
2) Decodes and checks for
valid instruction.
3) Executes the instruction.,
CPU Execution Unit
System Bus
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Section 1 UNIX/Linux Introduction
 Computer System Hardware

System Bus
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Section 1 UNIX/Linux Introduction
UNIX
Software
Architecture
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Section 1 UNIX/Linux Introduction
 UNIX Software Architecture
 Application User’s Interface ( AUI )


Applications:
 Contains all applications (Tools, Commands, and
Utilities) available to Users.
 Filesystem: cp, mv, rm, mkdir, mkfifo, ls, cd.
 Text Processing: vi/vim, emacs, more, less, diff.
 Programming: make.
 User Environment: su, uname, who, whoami
 Application manipulates system resources by invoking
kernel code through library functions or system calls.
UNIX Shell:
 Program that starts running when logon and interprets
the commands that are entered.
 echo, expr, sleep, test, tee.
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Section 1 UNIX/Linux Introduction
 UNIX Software Architecture
 Application Programmer’s Interface ( API )


Library and system call interfaces are Application
Programming Interfaces (API) used by user programs to
invoke kernel code.
System Call Interface:




Entry points into the Kernel.
All system resources managed by the Kernel: UNIX provides
access to Kernel code through function (system) calls.
Manipulate processes, Files, and other System Resources
(allocate/deallocate memory, access printer).
Language Libraries: C, C++, Java, FORTRAN, etc.



Set of prewritten functions available to programmers to use
during software development.,
C Language Libraries: printf, memcpy, strcmp, memcmp.
C Language Math Library: Functions for mathematical
operations.
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Section 1 UNIX/Linux Introduction
 UNIX Kernel: UNIX Operating System


Kernel Process Management: Creates, Suspends, Terminates,
Schedules, Communicate, and maintain States.
Provides communication between processes: Same Computer
System or through Network between Computer Systems.
 Primary Inter-Process Communication (IPC) Mechanisms.
 Pipe: Temporary channel residing in main memory used
by two or more related processes.
 Named Pipe ( FIFO ): Permanent communication
channel on disk and used as IPC between two or more
related processes.
 BSD Socket: Temporary channel allows two or more
processes to communicate through network ( Internet ) or
same computer.
 Client-Server Applications (BSD): Web Browsers, Electronic
Mail, Telnet, SSH, FTP.
 Distributed Network Architecture (BSD): P2P

Napster, BitTorrent, uTorrent
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Section 1 UNIX/Linux Introduction
 UNIX Software Architecture
 UNIX Kernel (Cont)

Disk Management:


Main Memory Management:




Disk scheduling Algorithm (multiple requests).
Keeps status of physical memory, either allocated or free.
How memory is allocated to processes: Contiguous Allocation, Paged
Allocation, Segmented Allocation.
Process Address Space: Allocates space to a process and prevents
user memory space volation.
File Management:


File creation/removal. Directory creation/removal.
File and directory attribute maintenance.
 Device Drivers:
 Executes on behalf of the UNIX kernel when a user
command or application needs to perform hardware-related
operations.
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Section 1 UNIX/Linux Introduction
 UNIX Usage


UNIX System:
 Is a Multi-process, Multi-user, and Interactive Computing
Environment.
 Designed for Multi-User computing environment (sharing the
Computer System).
 Portability is major trademark of UNIX.
UNIX Basic Connections:
 Local area network Connection
 Terminal connected to a computer server through LAN to
the UNIX computer system.
 Internet Connection
 PC running Telnet or ssh software connecting through
Internet to the UNIX computer system.
 Stand-alone Connection
 User logged on to UNIX computer system (Desktop
UNIX).
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Section 1 UNIX/Linux Introduction
 UNIX Usage

UNIX Basic Connections:
 Local area network Connection
Compute Server
Connection to a Local or Wide
Area Network
RS-232
Serial Ports
Modem
Connection.
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Terminal Server
connects to
Network Interface
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Section 1 UNIX/Linux Introduction
 UNIX Usage

UNIX Basic Connections:
 Standalone Connection
RS-232
Serial Ports
Modem
Connection.
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Connection to a Local or Wide
Area Network
Terminal Server
connects to
Network Interface
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Section 1 UNIX/Linux Introduction
 UNIX Usage
 UNIX Basic Connections:
 Internet Connection
Connection to a Local
or Wide Area Network
PC running Telnet or ssh
software connecting
through Internet to the
UNIX computer system.
Modem
Connection.
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Section 1 UNIX/Linux Introduction
 Logging On


Logging Out: <Ctrl> <D>
Bash Shell


Login: /etc/profile
Login: Script searched in the following order,


Shell: Started in Terminal Emulator or GUI (xterm).


1) $HOME/.bash_profile, 2) $HOME/.bash_login, 3) $HOME/.profile
$HOME/.bashrc
Logout:

$HOME/.bash_logout
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Section 1 UNIX/Linux Introduction
 UNIX Command
 Shell Environment



Console: Properties and appearance.
Shell session: User Interaction with the system requires
information compiled by the shell to determine its behavior
and access to system resources.
Shell Variables or local symbols are contained exclusively in
the shell in which they are defined (local session).


Variable = Setting
Variable is a Shell Variable.
Setting is the value of the Shell Variable.
Shell Environment Variables or global symbols are settings
for its local session and spawned child sessions.


export Variable = Setting
The Environment Variable for all subsequent child sessions
must be placed in Configuration Files (i.e. /etc/profile,
/etc/bashrc, ~/.bash_profile, ~/.bashrc).
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Section 1 UNIX/Linux Introduction
 UNIX Command

Shell Environment

Global Environment

~/.bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
PATH=$PATH:$HOME/bin
export PATH

User Local Environment

~/.bashrc
# Source global definitions
if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi
# User specific aliases and functions
export PATH=$PATH:$HOME/rpi/tools/arm-bcm2708/gcc-linaro-arm-linux-gnueabihfraspbian/bin
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Section 1 UNIX/Linux Introduction
 UNIX Command
$ command [ [ - ] option (s) ]







[ option argument (s) ]
[ command argument (s) ]
$: Shell prompt from the computer.
[..]: Enclosed is not always needed.
Command: Name of the valid UNIX command for the shell.
[-option(s)]: Command modifier that change behavior of command.
[option argument(s)]: option modifier that changes behavior of -option.
[command argument(s)]: Command parameter(s) are objects that are
affected by command.
NOTES:




Space separates command, option, option arguments, and command
arguments.
Space optional between multiple options or multiple option arguments.
Order of multiple options or option arguments irrelevant.
Space optional between option and option argument.
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Section 1 UNIX/Linux Introduction
 UNIX Command
 $ ls

$
ls -la

$
Command (ls) and two options (l and a).
ls -la m*

$
Only command.
Command (ls), two options (l and a) and command argument
(m*).
lpr -Pspr -n 3 proposal.ps

Command (lpr), two options (P and n), two option arguments
(spr and 3), and command argument (proposal.ps).
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Section 1 UNIX/Linux Introduction
 Microsoft Windows PuTTY Connection
User on PC running Windows OS start the
PuTTY program to connect to the remote
server through the remote server’s host name
or IP address.
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Section 1 UNIX/Linux Introduction
 Microsoft Windows Command Dialogue Box
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Section 1 UNIX/Linux Introduction
 PuTTY Connection
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Section 1 UNIX/Linux Introduction
 History


Linux File System derived from Minix File System (later Xia File System).
Linux implemented Extended File System (ext, ext2, ext3, and ext4).
Max file
system size
Max file size
Max file
name size
Minix File
System
64 MBytes
64 MBytes
16 Bytes
Block file System.
Extended File
System
2 GBytes
2GByte
255 Bytes
Block File System.
Second
Extended File
System
32 TBytes
2 TBytes
255 Bytes
Block File System.
Third
Extended File
System
32 TBytes
2 TBytes
255 Bytes
Journaling File System.
Fourth
Extended File
System
10**6 TBytes
16 Tbytes
255 Bytes
Journaling File System or
Block File System.
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Section 1 UNIX/Linux Introduction
 History
 Virtual File System (VFS) provide level of
abstraction between user and different file
systems.
 Using a common set of API functions, a large
variety of file systems can be supported on a large
variety of storage devices.

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Read function unaware of system
types (i.e. ext2, ext3, ext4, or NFS)
and unaware of storage medium file
system is mounted.
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Section 1 UNIX/Linux Introduction
 Linux
Directory Structure
/boot – Linux bootup files (i.e. Linux Kernel)
/etc – Linux system configuration files.
vmlinux
boot
/
root
etc
bin
usr
sbin
var
dev
mnt
home
/etc/inittab – Processes started at bootup (i.e. Runlevel)
inittab
fstab
mount
Summer 2015
/etc/passwd – Users are defined and user accounts.
/bin – Linux system binaries.
/sbin/init – Process runned during boot process.
bin
grep
/usr/bin – Applications for the users.
/lib – The shared libraries for dynamically linked modules.
init
/var – Data changes when the Linux system is running.
log
/var/log – The running Linux system updated log files.
tty0
/dev – Devices that are available to Linux system. Devices are
treated like files and devices can be read/written as files.
cdrom
/mnt – Storage devices (i.e. hard disk, CD-ROMs) must be attached
to some directory before accessing. Directores are the mount points.
student1
lib
proc
/etc/fstab – File systems and mount points.
passwd
/home – Each users have own directory and only place normal users
are allowed to write.
/proc – Special directory containing information about the kernel.
devices
/proc/devices – List of devices configured into current kernel.
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Section 1 Unix/Linux Introduction
 File Maintenance




Home Directory: User Login to /home/<username> in shell.
Current Working Directory (CWD): Directory shell currently
in. Only one current working directory active at one time.
Pathname: Textual designation of directory or file.
Organize group of files into “bins” or directories, for example,
according to the file contents subject matter or dates of
creation.
Parent of
/
home
/home/sau/myfile2
/home/sau/first/…
/home/sau/myfile1
CWD.
CWD =
sau
Children of
CWD.
sau
myfile2
first
myfile1
...
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Section 1 UNIX/Linux Introduction
 File Maintenance Commands
 Viewing / Creating / Deleting / Managing Files

cat, more, cp, mv, rm, ls
/
home
$ cat > myfile1
Use the cat to add plain text.
sau
<Ctrl-D>
$ more myfile1
myfile2
first
myfile1
Use the cat to add plain text.
$ cp myfile1 myfile2
$ mv myfile2 renamed_file
renamed
_file
$ mv “latest revisions” late.txt
mv: cannot stat `latest revision': No such file or directory
$ rm renamed_file
$ ls
myfile1
$
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Section 1 UNIX/Linux Introduction
 File Maintenance Commands
 List Files and Directories Properties


Options: -F (“/”=Directory, “*”=Binary, “<“=Executables,
“@”=Symbolic Link), -a (All files, including hidden files), -i
(Inode numbers), -l (File Access Mode, Link Count, Owner,
Group, File Size, Mod Time).
Column 1:
Type of file, “d” directory, “l”
ls -la
symbolic link, “-” ordinary or
drwx------ 37
drwxr-xr-x 8
drwxrwxr-x 9
-rw-rw-r-- 1
Column 2:
Number of links
to the file.
Column 3:
Username of
owner.
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regular file. Access mode for
pi pi
4096 2014-09-03 16:57 .
file.
root root 4096 2014-01-14 18:53 ..
pi pi
4096 2014-07-18 01:06 raspi
pi pi
275 2014-03-14 03:15 minicom.log
Column 5:
Number of bytes of the file.
Column 4:
Group name of file.
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Section 1 UNIX/Linux Introduction
 File Maintenance Commands

Creating / Deleting / Managing Directories
 mkdir, cd, pwd, rmdir
$ mkdir first
$ cd first
$ pwd
/home/sau/first
$ cd
$ pwd
/home/sau
$ cp myfile myfile2
$ ls my*
myfile myfile2
$ mv myfile2 first
$ rmdir first
rmdir: first: Directory not empty
$ rm –r first
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home
sau
first
myfile
46
Section 1 UNIX/Linux Introduction
 UNIX Help (man Command)



Obtaining Help with “man” Command
UNIX Reference Manual pages has 8 Sections
 Section 1 most users.
 Section 2 most software developers.
Name: Synopsis: Description: List Of Files: Related Info: Errors:
Warnings: Known Bugs
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Section 1 UNIX/Linux Introduction
 UNIX Help (man Command)
man [options][-s section] command-list
$ man ls

LS(1) FreeBSD General Commands Manual LS(1)
NAME
ls - list directory contents
SYNOPSIS
ls [-ABCFGHLPRTWZabcdfghiklmnopqrstuwx1] [file ...]
DESCRIPTION
For each operand that names a file of a type other than directory, ls displays
its name as well as any requested, associated information. For each operand
that names a file of type directory, ls displays the names of files contained
within that directory, as well as any requested, associated information.
If no operands are given, the contents of the current directory are displayed.
If more than one operand is given, nondirectory operands are displayed first;
directory and nondirectory operands are sorted separately and in lexicographical
order.
The following options are available:
Press <SPACE> to continue, or q to quit q
$ man -s2 read
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Section 1 UNIX/Linux Introduction
 UNIX Help (man Command)
man [options][-s section] command-list
$ man –s2 read

READ(2)
NAME
Linux Programmer’s Manual
READ(2)
read - read from a file descriptor
SYNOPSIS
#include <unistd.h>
ssize_t read(int fd, void *buf, size_t count);
DESCRIPTION
read() attempts to read up to count bytes from file descriptor fd into
the buffer starting at buf.
If count is zero, read() returns zero and has no other results.
If
count is greater than SSIZE_MAX, the result is unspecified.
RETURN VALUE
On success, the number of bytes read is returned (zero indicates end of
file), and the file position is advanced by this number. It is not an
error if this number is smaller than the number of bytes requested;
this may happen for example because fewer bytes are actually available
right now (maybe because we were close to end-of-file, or because we
: q
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Section 1 UNIX/Linux Introduction
 UNIX Help (man Command)
man [options][-s section] command-list
$ man –k passwd

[pi@sau (Fri Sep 05 - 02:43:18)$ man -k passwd
chpasswd
(8) - update passwords in batch mode
fgetpwent_r [getpwent_r] (3) - get passwd file entry reentrantly
getpwent_r
(3) - get passwd file entry reentrantly
gpasswd
(1) - administer the /etc/group file
hesiod_free_passwd [hesiod_getpwnam] (3)-Hesiod functions for retrieving passwd …
hesiod_getpwnam
(3) - Hesiod functions for retrieving passwd information
hesiod_getpwuid [hesiod_getpwnam] (3) - Hesiod functions for retrieving passwd …
htpasswd
(1) - Manage user files for basic authentication
ldappasswd
(1) - change the password of an LDAP entry
lpasswd
(1) - Change group or user password
lppasswd
(1) - add, change, or delete digest passwords
pam_localuser
(8) - require users to be listed in /etc/passwd
pam_passwdqc
(8) - Password quality-control PAM module
pam_passwdqc
(rpm) - Pluggable password quality-control module.
passwd
(1) - update a user's authentication tokens(s)
passwd2des [xcrypt] (3) - RFS password encryption
passwd
(5) - password file
. . .
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Section 1 UNIX/Linux Introduction
 UNIX Help


man -f <keyword>
whatis <keyword>

Search the whatis database for abbreviated descriptions
of each “keyword” and print a one-line description.
$ whatis login set setenv
login(1) -sign on
set(1) -set runtime parameters for session
setenv (1) -change or add an environment variable
$
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Section 1 UNIX/Linux Introduction
 UNIX Utility Commands



Examining System Setups
 whereis, whoami
$ whoami
sau
$ whereis mkdir
mkdir: /usr/bin/mkdir
General Utility Commands
 lpr, cal
$ lpr –Pspr order.eps
Communication Commands
 write, who, mesg y, mesg n
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Section 1 UNIX/Linux Introduction
 UNIX Utility Commands: write
student1 pts/2
[student1@sau (Fri Sep 05 - 18:01:38)$ mesg y
[student1@sau (Fri Sep 05 - 18:01:41)$ who
pi
pts/1
2014-09-05 17:51 (:0.0)
student1 pts/2
2014-09-05 17:56 (10.1.110.198)
student2 pts/3
2014-09-05 17:59 (10.1.110.198)
[student1@sau (Fri Sep 05 - 18:01:43)$
[student1@sau (Fri Sep 05 - 18:02:52)$ write student2 pts/3
Hello student2
[student1@sau (Fri Sep 05 - 18:04:20)$
Message from [email protected] on pts/3 at 18:04 ...
I am fine.
Where are you?
EOF
student2 pts/3
[student1@sau (Fri Sep 05 - 18:01:38)$ mesg y
[student2@sau (Fri Sep 05 - 18:10:50)$ who
pi
pts/1
2014-09-05 17:51 (:0.0)
student1 pts/2
2014-09-05 17:56 (10.1.110.198)
student2 pts/3
2014-09-05 17:59 (10.1.110.198)
[student2@sau (Fri Sep 05 - 17:59:49)$
Message from [email protected] on pts/2 at 18:03 ...
Hello student2
EOF
[student2@sau (Fri Sep 05 - 18:04:30)$ write student1 pts/2
I am fine.
Where are you?
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Section 1 UNIX/Linux Introduction
 UNIX Command Alias


The alias command can be used to create pseudonyms
(nicknames) for commands
Syntax for the alias command is:

alias [name [ = string ] …] Bourne, Korn, Bash shells


alias [name [ string ] ]


Create aliases in term profile (i.e. .login) or shell startup script (i.e. Bash
in .bashrc file).
C shell
Create aliases in term profile (i.e. .login) or from command line or shell
startup script (i.e. .cshrc).
Useful Aliases

Bash shell
C shell
alias dir=“ls -la”
alias rename=“mv”
alias ll=“ls –ltr”
alias dir “ls -la \!*”
alias rename=“mv \!*”
alias ll=“ls –ltr \!*”
function foo() { mv “$@”; }
Alias rename=foo
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Section 1 UNIX/Linux Introduction
 UNIX
Useful Commands
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Section 1 UNIX/Linux Introduction
 UNIX
Useful Commands
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