UNIX Training Basics

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Fundamentals of UNIX


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Agenda

UNIX Basics Definition , History, ArchitectureVarious flavors, Design Principles

UNIX System Processes

File System

Types of Files

Types of ShellsBasic UNIX Commands


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What is UNIX ?

Multi User, Multi Tasking, Multi Processing, TimeSharing, Portable, Networking, Strong Security (Secure)Operating System

Powerful Operating System

Written in High Level Language

Hierarchical Directory Structure

Supports internet


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How the Name UNIX appeared ?

MULTICS(MULTiplexed Information & Computing Service)1965

Bell Labs + GE + MIT

UNICS( UNiplexed Information & Computing Service )1969

Bell Labs

Ken Thompson along with Dennis Ritchie

UNIX

Bell Labs Brian Kernighan

1969


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History of UNIX

1969, First developed

Ken Thompson & Dennis Ritchie,

Research Group at Bell Laboratories

Version 1, 2 - Assembly Language.Version 3 - C Language, Bell Labs


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History of UNIX Versions


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UNIX Flavors

Sun Solaris 10

HP-UX 11i v3

Santa Cruz Operation (SCO)

LINUX

AIX (Advanced Interactive eXecutive)(IBM)

MINIX

XENIX


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Hardware

System Call Interface

General UNIX Architecture

UNIX Commands

& Libraries

User Applications

Kernel

HardwareDATABASE Compilers

SHELLs

ksh, sh, csh etc.


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What is Kernel ?

Internal Algorithms + System Calls

Interacts directly with the Hardware

Provides File system, CPU scheduling, Memory management,

and other OS functions like :

schedules tasks

manages data/file access and storage

enforces security mechanisms

performs all hardware access

Provides services to user requests by interacting withHardware.


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Unix Design PrinciplesEverything treated as File & Process (Imp. Components)

e.g. Terminal treated as a file /dev/tty1

A job when run treated as series of running Process

User interacts with the KERNEL through SHELL(K Shell, C Shell,Bourne Shell etc.)

Multi Processing System One process creates new process etc.,distribute processes to CPUs

Ability to increase priority of a Process, kill process etc.

Can Submit a job (Script) in foreground (Default) or background.Most people survive on a Small handful of UNIX Commands


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What is a Process ?

Fundamental to almost all operatingsystems = program in execution

Has usually separate address space

It is an instance of a running program.


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Processes in Windows

Windows Task Managerin

Windows NT /

Windows XP/Windows 2000 /


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Process CreationProcesses are created during:

system initialization (Init, Swapper etc.)

by another process

user request (from shell)

Batch job (timed, Unixat

orcron

)Foreground processes interact with user

- The output would be redirected to the screen/terminal.

Background processes (daemons)

- Any process/command can be run in the background by using &at the end. Meanwhile, other processes can be run.


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UNIX Processes/home/ginger>ps -ef|more

UID PID PPID C STIME TTY TIME CMD

root 0 0 0 08:09:31 ? 0:38 sched

root 1 0 0 08:09:31 ? 0:02 /etc/init -

root 2 0 0 08:09:31 ? 0:00 pageout

root 3 0 2 08:09:31 ? 08:49 fsflush

root 2262 1 0 08:13:53 ? 0:00 /usr/lib/saf/sac -t 300

root 988 986 0 08:11:31 ? 0:00 htt_server -port 9010 -syslog -message_locale C

root 1078 1 0 08:11:35 ? 0:00 ./ns-admin -d /apps/suitespot/3.62/admin-serv/config

root 11 1 0 08:09:35 ? 0:00 /platform/SUNW,Sun-Fire-15000/lib/cvcd

root 22 1 0 08:09:36 ? 0:06 vxconfigd -m boot

root 825 1 0 08:10:41 ? 0:00 /usr/platform/SUNW,Sun-Fire-15000/lib/sckmd

root 1196 1 0 08:11:36 ? 0:01 /usr/sbin/auditd

root 76 1 0 08:10:02 ? 0:00 /usr/lib/sysevent/syseventd

root 598 1 0 08:10:29 ? 0:01 /usr/lib/picl/picld

root 879 876 0 08:10:48 ? 2:40 /usr/lib/autofs/automountd

Each process is identified by a numbercalled Process Identifier (PID)PPID stands for Parent of the Process


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UNIX File Hierarchy

/(Root)

binsbin dev etc lib stand tmp usr


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UNIX File Hierarchy

UNIX Directories with the information it contains

bin all binaries, compilers etc.

dev all device files

etc all sys adm files, commands

lib all library files

stand all apistmp all temp files

usr all user related files


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Types of filesOrdinary file (data file, text file etc.)

Directory (also treated as file)

Device fileLink File

Sticky bit file


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ShellWhat is a Shell ?

An Interface between User & Kernel

An environment for aScript/command provided to the user

to run/execute commands.

Broadly used Types of Shells:

1. K Shell /bin/ksh (Largest)

2. C Shell /bin/csh

3. Bourne Shell /bin/sh

User

Shell

UNIX O.S.(Kernel)

Hardware


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UNIX Variables( Script Variables)Variables are a way of passing information from the shell to programs when

you run them

Variables SYSTEM Variables / Environmental Variables

e.g. LOGNAME, PATH, SHELL, PS1, HOME, PWD etc.

USERDEFINED Variables

i=10

v_string=jpmorganchase

ONLY String text needs to be enclosed


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Identify Shell I am working with(using SYSTEM Variable)

$echo $SHELL

/bin/ksh => K Shell

/bin/sh => Bourne Shell

/bin/csh => C Shell

Switch to a Particular Shell

1. K Shell to Bourne Shell

$/bin/sh2. K Shell to C Shell

$/bin/csh


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What is a UNIX Command ?

Binary file that resides in /usr/bin, /usr/local/bin or /bindirectory

What happens when executed ?

When executed by user/through program, sends the userrequest to KERNEL that understands what request is made andprovides services to the User command.


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UNIX Commands

Connect to a UNIX Machine

$telnet

Prompts for login & password, after successful

authentication, displays $ prompt.To find out in which path (directory path) I am right now

$pwd Present Working directory

To find out the OS you are working in

Uname


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UNIX Commands

HOME Directory:

This is the directory along with its path that appears wheneverwe login to a Unix Machine by entering right login/passwd and $prompt is displayed.

The directory along with its path can be found by using thecommand pwd

This Directory Path is stored in SYSTEM Variable HOME.

List all files and subdirectories in Ascending order of file creationie., latest file created present at the last line

$ls lrt


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By default a File has a Read and Write permission but no executepermission unlike a Directory.


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UNIX CommandsTo see the help / manual of a UNIX Command

man $man ls

To print the system date and time $date

To create a NEW directory $mkdir dir1

To change from one directory to another existing directory

$cd eg. cd dir1

To create a new empty file - $touch

To Create a new file or a shell script, use VI editor


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UNIX CommandsDisplay the contents of a file at Command Prompt.

cat

$cat test.txt

To find the no. of lines, chars, words in a file

wc

$wc test.txt

To change the Name of an existing file

$mv file1 file1.sh

To remove a file from a directory and place it in a new directory

$mkdir new_dir #First creating the NEW directory

$mv file1 ./new_dir


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UNIX CommandsTo have a back-up of an

i) existing file

$cp file1 file1.bak

ii) existing directory (with files in it)

$mkdir backup_dir

$cp log.* /backup_dir

File Permissions - Categorized for 3 types of Users

1) User (Owner) u the person who is able

to login successfully and is creating the file.

2) Group g the group to which the user belongs to

3) Other o All other users


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UNIX Commands

To give Write Permission for the file.

$chmod u+w ScriptFile

To give eXecute permissions to a file (Shell Script) inorder to run

the file.

$chmod u+x ScriptFile

To Remove Write Permission from the file.

$chmod u-w ScriptFile

To Remove eXecute permissions from a file (Shell Script).

$chmod u-x ScriptFile


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UNIX Commands

To Check whether an Application/Script process is Running

$ps ef|grep

Where e show processes of ALL Users.

f - show FULL ie.,

process IDs & PPIDs

Kill an active running process

1. Obtain the Process ID of the process

$ps ef|grep

2. Kill the Process by using its Process ID obtained from above.

$kill -9


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UNIX Commands

To have a tree view of the processes running for an Script/jobthat is run.

1. Obtain the Process ID of the process

$ps ef|grep

2. Use ptree command for the Process ID obtained from above.

$ptree

To Search for a pattern (a word) in a file and display the record.

grep

$grep error 20061118.log

Here we are searching for the occurrence of error by usingkeyword error in the log file.


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UNIX Commands

Search irrespective of CASE sensitivity (UPPER/LOWER case) of thepattern to be searched.

$grep i error 20061118.log

In the Current Directory, to search for a pattern when file name isnot known

$grep il error *.log

To search for errors and warning appearing in a Log file

$egrep i error|warn 20061118.log


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UNIX Commands

To display list of ONLY directories

$ls lrt|grep d

To view a Growing Log file

$tail f


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Summary


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Common Discussions /Questions

?


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Thank U

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UNIX Training Basics

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