1. Unix : Introduction and Commands
Fundamental of information technology

2. Objectives Introduce Operating Systems concepts
Provide a brief history of the Unix operating system.
Provide a brief overview of the Unix system
Introduce the Unix command structure
Introduce a simple Unix session including:
Logging on
Changing Passwords (passwd)
cal [mon [year]]
date
man Unixcommand
Logging off (exit)

3. Unix A Brief History
Developed for AT&T at Bell Labs by Ken Thompson in 1969.
Rewritten in C by Dennis Ritchie
Developed by programmers for programmers
Became widely available in 1975.
University of California, Berkeley created the Berkeley Software Distribution (BSD) version.
AT&T combined their version with BSD, XENIX, and SunOS to create System V

4. Unix: What’s in a name? Unix may be shown as UNIX ®, Unix, Unix®
UNIX® is a register trademark of The Open Group (as of 2007) the certifying body of the UNIX trademark

5. What Unix does Control program for computers managing:
Processes
Multi users
Memory
Files
Provides support utilities called commands for:
Executing programs
File management
File editing
Process management

6. Unix Overview
H/W
Kernel
Shell
interfaces
User
Unix

7. Overview of Unix System
Kernel & Shell
Unix/Linux is operating system (OS).
Unix system is described as kernel & shell.
Kernel is a main program of Unix system. it controls hard wares, CPU, memory, hard disk, network card etc.
Shell is an interface between user and kernel. Shell interprets your input as commands and pass them to kernel.
User
input
Shell
Kernel

8. Unix Overview (cont.) Multi-user & Multi-process
Many people can use one machine at the same time.
File & Process
Data, directory, process, hard disk etc (almost everything) are expressed as a file.
Process is an running program identified by a unique id (PID).

9. Unix Components
Kernel
Filesystem
Shell
Utilities

10. Unix Operating System Runs on virtually every manufacturer's hardware
Works the same way on every computer

11. Relation of Files & Directories
Root is like a file cabinet.
A directory is like a file drawer
A subdirectory is like a folder within a drawer.
A path is a list of directories & subdirectories from root to a specific file or subdirectory. /
Root
Directories
Files
UNIX File System

12. UNIX Directory Structure
At login, you are in your home directory.
This is your current working directory.
All files and directories below your home
directory usually belong to you.
You change your working directory by
changing to another directory (cd).
UNIX File System

13. Pathnames Absolute Pathname: shows the absolute position of a file
or directory in the hierarchy;
/home/user2/bif/docs
begins with a slash (/); and
describes how to get to the file from the root.
UNIX File System

14. Filesystems A file is identified by Combining directory pathnames
To the filename /usr/local/meeting /
root
usr
files
local
meeting
UNIX File System

15. Basic Commands Commands ls show files in current position
cd change directory
cp copy file or directory
mv move file or directory
rm remove file or directory
pwd show current position
mkdir create directory
rmdir remove directory
less, more, cat display file contents
man display online manual
“ls” stands for list.
Pwd stands for present working directory

16. Basic Commands Commands su switch user passwd change password
useradd create new user account
userdel delete user account
mount mount file system
umount unmount file system
df show disk space usage
shutdown reboot or turn off machine
“su” means switch user. When you have several user account on one machine.

17. Directory Commands mkdir making a directory
cd changing your working directory
pwd printing your working directory
ls listing the contents of a directory
rmdir removing a directory
UNIX File System

18. Directory Commands - mkdir
Make directory under current working directory
host% mkdir docs
Make directory under subdirectory
host% mkdir docs/index
Make directory and subdirectory
host% mkdir docs docs/index
Make directory using absolute path
host% mkdir /usr/tmp/abc
User1
(cwd)
docs
User1
(cwd)
docs
index
UNIX File System

19. Common Error Messages:
mkdir: dirname: File exists mkdir: dirname: Permission denied
UNIX File System

20. Directory Commands - cd
userx
host% cd docs host% cd /usr/tmp/abc/docs host% cd ~abc/docs host% cd host% cd ..
docs
/usr
tmp
abc
docs
~abc
docs
UNIX File System

21. Common Error Messages:
pathname: No such file or directory
pathname: Permission denied
UNIX File System

22. Directory Commands - pwd
Determining the current working directory:
host% pwd
/scc/users/chitspit/bif
where:
/ root
scc/ file system followed by the delimiter (/)
users/ subdirectory of scc
chitspit/ directory followed by the delimiter (/)
bif current working directory
UNIX File System

23. Directory Commands - ls
host% ls bin mbox remodel complex.f outdis test host% ls -sF (Multiple options may be specified) 15 bin/ 256 mbox 3 remodel/ 34 complex.f 6 1 test* host% ls ~chitspit/bin au clst prod show xref
cwd
UNIX File System

24. Process Management commands
Process is a unit of running program.
Each process has some information, like process ID, owner, priority, etc.
Commands
kill Stop a program. The program is specified by process ID.
ps Show process status

25. Some Unix Shells Bourne Shell (sh) Bourne Again Shell (bash)
Korn Shell (ksh)
C Shell (csh)
many others… 25