CIS 14A - Operating Systems (UNIX)

CIS 14A - Operating Systems (UNIX)
Markus Geissler, MBA Nghiep Nguyen, MSEE

About the Instructor... Nghiep Nguyen, MSEE -Sacramento High School, AA in Math and Science Sacramento City College, BS in Electrical Electronics Engineering UC Davis, 1987 -MS in Electrical Electronics Engineering CSUS, 1993

Experience - Electronic Engineer, 87 - 90 Sacramento Army Depot
Write Test Program Sets for Unit Under Test for Tomahawk Computer. - Software Engineer, McClellan Air Force Base Operational Flight Program for A-10

Experience - Electronic Engineer, 95 -96 Tinker Air Force Base
B-2 Stealth Bomber - Software Engineer, McClellan Air Force Base A-10 aircraft

Experience - Associate Programmer 1/98 - 10/98
P.O.S.T: Work with PowerBuilder, SQL - Associate Systems Software: /98 F.T.B: Sybase DBA - Systems Software Specialist, 11/98 to Present Legislative Data Center Unix (Sun Solaris) System Administrator

Experience Adjunct Faculty: 8/97 to Present Cosumnes River College
Unix, Internet, HTML Java, Visual Basic Visitor Lecturer: 8/02 – 6/03 California State University, Sacramento Visual Basic, Java

Office Hours None E-mail: nghiep_nguyen@yahoo.com
Work: Web site:

Textbook(s) Required Strongly recommended
UNIX System V - A Practical Guide (Third Edition) by Mark G. Sobell Addison-Wesley Publishing Company Strongly recommended CIS 14A Lecture Slides By Markus Geissler Download from website

Reverse Flows of Knowledge
Examinations Hands-on in Classroom One make-up exam per person at the instructor’s convenience No more than 90% possible on makeup exams Homework projects

Other Resources UNIX Utility Program Reference
Back of textbook (starting on p. 521)

Things You Should Know Before Starting This Course
A basic understanding of the components of a computer system CIS 1

UNIX What exactly is UNIX? Computer Operating System
large set of utility programs general user programmer communication administrative commands 1

Operating System Definition: An operating system (OS) is a set of instructions that manages all computer operations and provides an interface between user(s) and system resources.

UNIX Computer operating system (OS) Large set of utility programs
Based on C programming language Used in enterprise networks Operating System Disk Drive Monitor Keyboard Mouse Printer Application

What Can UNIX Do For You? General user applications
Programming environment Typesetting tasks Communication applications Administration commands

The Inner Workings of a Computer - Summary
Central Processing Unit Memory Storage I/O

Central Processing Unit (CPU)
“Brain” of the computer Executes instructions from programs and processes Manufacturers include Intel Advanced Micro Devices (AMD) Cyrix Motorola Sun Microsystems

Memory RAM (Random Access Memory) Volatile
Information disappears when electrical power to RAM is interrupted Capacity measured in Megabytes (MB) Access speed measured in Nanoseconds (ns) Holds data before and after CPU processes them Program instructions Application data

Storage Hard disk Floppy/ZIP®/JAZ®/SyQuest® disks
Installed inside computer’s case Floppy/ZIP®/JAZ®/SyQuest® disks Portable; require disk drive Disks are typically non-volatile Data called into memory when needed Capacity measured in Gigabytes (GB) Magnetic Tape Largely used for data backup

Input/Output (I/O) Reads input from a device into memory
Keyboard Mouse Writes output from memory to devices Monitor Printer Disk drives are input and output devices long term storage devices

UNIX Facts Created in 1969 Based on C language
by Kent Thompson Based on C language AT&T (Bell Labs) shared UNIX with colleges and universities Colleges made enhancements Berkeley Software Distribution (BSD) See Introduction to UNIX by Fiamingo, DeBula and Condron

Linux Compact version of UNIX for PC Not yet standardized
Created by Linus Thorvald Not yet standardized Supported by a large, active user community Free versions available on the Internet approx. $50 for RedHat Linux

Major UNIX Components Kernel Shell File System Shell & Utilities
Hardware

Kernel Core of UNIX OS Manages hardware, memory and file system resources Controls transmission of information between user application and CPU Stores information about the arrangement of the computer system and the network

Shell Interface between user and OS Korn shell Bourne shell C shell
Most robust features Bourne shell Subset of Korn shell C shell Not related to other two shells Most widely used in SunOS

UNIX OS Components Shell Three types of Shells: Korn, Bourne, and C
Shell program are interpreted, not compiled commands are read and executed one by one compiled program is read and converted to a machine language then execute all at once slower than compiled language such as C Three types of Shells: Korn, Bourne, and C 8

Shell History Bourn -- Steve Bourne at AT&T Bell Labs
Original UNIX shell -- compactness & speed lack features for interactive use C -- Bill Joy (SUNW) friendly features for users larger and slower than Bourne Korn -- David Korn of AT&T Bell Labs faster than C shell, will run Bourne Script

File System Organizes data on disk in a hierarchical structure of directories File Program or data Directory/folder Similar to file drawer Each disk has root directory Subdirectory Directory/folder within other directory

File System Structure Root (/) /etc : system administration files
/usr : executable commands, s.a. utilities /opt : third-party software /export/home or /home : user’s home directory

Multitasking OS Used to approach 100% of computer resource utilization while increase user productivity Reduced cost per user Time slicing Users can run multiple processes Increases user productivity UNIX refers to task as “process” Usually maximum of 25 concurrent processes per user session

Multi-User OS Supports 1 - 2000 users
Users share system resources To approach 100 percent in computer resource utilization while reducing the cost per user Share system resources

Interactive Mode Immediate response to keyboard or mouse input
“No news is good news” Display returns shell prompt after commands are issued Different shells have different prompts Detailed feedback only when errors made

Networking Terms Host - a computer system
Host Name - a unique name for a system IP address - a number used by networking Network connects machines to enable comm. between users on other systems. Server provides resources to one or more clients on the network 12

More Terms Client is a machine that uses services from one or more servers on a network NFS (Network File System) enables files to be shared across the network. NIS (Network Information Services) enables system administration functions to be centralized on a server. Client-Server

Network Connects computers to enable communication between users on multiple systems

Clients vs. Servers Server Client Front end vs. back end
Provides resources to one or more clients on the network Usually requires more powerful equipment than clients Client Computer that uses services from one or more servers Front end vs. back end

Set Up User Account must have it set up before a user can log in contains essential user account info User name identifies a user to the system is created by System Administrator. Bring your class registration/schedule to the computer lab. The lab assistant will set up the Unix account for you 15

Logging into CRC’s LAN Login name Initial password: new2lan
First four letters of your last name Last four digits of student ID number Initial password: new2lan Change password right away

Password Security Do not choose a password that can be related to you!
Use a password that does not resemble a word in the dictionary Case sensitivity

Password Guidelines No less than six characters
Must contain at least two alphabetic characters and at one numeric or special character can have spaces, avoid special characters Cannot be login name or reverse New password must differ from old password by at least three characters

Accessing CRC’s UNIX Box
From Windows 95 or Windows NT Connect to Internet via your ISP Start, Run… TELNET or TELNET cosumn.crc.losrios.cc.ca.us

User Account Required for user login Identifies user to the system
Contains essential user account info Special environment settings for user Mail file

Logging into CRC’s UNIX Box
Log into system Initial username is same as for CRC’s LAN Initial password: new2mini Password will not display when typed Connection times out if you take too long Use exit command at the $ prompt to log out Also possible to disconnect within TELNET application

Entering UNIX Commands
Type commands with keyboard To correct a typing error, use Delete key NOT the Backspace key Press Enter key to send command to kernel

Changing Your Password
Use passwd command at $ prompt to change your password Type old password first Type new password twice Password will not be displayed when typed Password has to have at least one number in it Suggestion: Use same password as LAN account and add a number, if necessary

Getting Help in UNIX Use man command
Include command about which you want help man ls Use man ls | more to display one page at a time “Pipe” character Use Ctrl-C to interrupt file display If file is too long for one screen

Logging a TELNET Session
Record all activity within a session In TELNET utility Choose Terminal, Start Logging… Specify filename to which to log Local drive Network drive (U: drive in CRC lab) Up to 5 MB of space Choose Terminal, Stop Logging to stop writing to log file

The script Command Logs commands entered and results displayed
If no filename specified, script logs to file typescript Type exit to stop logging and close the log file

Printing Log Files Type lp filename to print to CRC lab
FTP file to home computer and print to local printer Printing from DOS Editor may be easier than from Notepad Potential problems with line breaks Turn off Word Wrap

UNIX Commands Command line format Options modify the command
command [ - option(s) argument(s)] Options modify the command Arguments tell the computer to what to apply the command Example cd [directory_name] ls [aFIR] [pathname]

Command Syntax Command Line Format command [option(s)] [argument(s)]
case sensitive blank space does matter since it is the delimiter for the shell do not necessary require all three parts 256 characters can be entered on a single command line 20

Commands passwd ls cd pwd cp rm mv 21

Commands cat more man mkdir rmdir date echo 21

Commands cal head tail wc grep find 21

Commands cd [ directory_name] pwd ls [ -aFlRt] [pathname] man command
21

Commands pwd -- present working directory cd -- change directory
mkdir -- create a new directory ls -- diplays contents of your directory l -- stands for long information F -- File type option a -- display all files (including customization files) R -- display recursively all directories/sub-directories and their corresponding files

Commands ls -F will display the following symbols next the listing of files: / for directory * executable file, shell script @ symbolic link none text file (ASCII)

Commands rmdir - remove directory
head -n --- displays the first n lines tail -n -- displays the last n lines wc -- word count command to display numbers of lines, words, characters diff -- to display the differences between two files.

Commands grep -- search for a pattern in a file or files

The cal Command Displays a calendar on the screen
Syntax: cal [ [month] year] Month from 1-12 Year from 1 to 9999 (!) Example: cal 1999 Displays the calendar for 1999 Eastern and Western calendars were combined in 1752 Check out September 1752!

The who Command Lists current system users Syntax: who
Example: who | sort -r Sorts users in reverse order Example: who | grep geisslm Allows you to check whether or not user geisslm is logged-in More details on examples later

Directory Structure / /home /dev /usr /bin /cis14a /user A /user B

Path Absolute path Relative path Type pwd at $ prompt
Present working directory /usr/cis14a/user B/home To change to directory, type cd /usr/cis14a/user B/home Relative path From /usr/cis14a/user B directory, type cd home

File Path absolute path -- Starts with / (stands for root directory) and go to where you want to go relative path -- start from where you are and move to sub-directory or parent directory

The cd Command Navigate directory structure
Type cd .. at $ prompt to change to parent directory Directory above current directory Type cd without attributes to change to home directory

Special Directory Names
. represents current directory .. represents parent directory “Above” current directory in directory tree Combine .. and “sibling” subdirectory name to move to “sibling” subdirectory To change from /usr/cis14a/user B directory to /usr/cis14a/user A, type cd ../user A

The ls Command List the contents of current directory
Type ls at $ prompt Directory entry types - (hyphen) for file d for directory

ls Command Options Directory entry type
User/group/other (world) permissions Number of links Owner name Owner group File size in bytes/blocks Date of file creation/last access Filename/directory name

ls Command Options ls -l lists details about contents
Long version ls -F shows slash (/) after directory name listing ls -R lists contents of entire tree (including subdirectories) Recursive

More ls Command Options
ls -r lists contents in reverse order ls -l (filenames) to list specific files ls -a displays all contents, including hidden ls -s lists size of file/directory in blocks 1 block = 512 bytes ls -i displays system’s item number for each directory entry

More ls Command Options
ls [directory name] lists contents of other directory

Combining ls Command Options
Possible to combine ls command options ls -a -F is the same as ls -aF | more option Say “pipe more” Lists one screen at a time Example: ls -R |more More on “piping” later

UNIX Filenames At least one character long Case-sensitive!
Maximum length: 255 characters Case-sensitive! Uppercase and lowercase characters are distinct Unlike DOS or Windows 9x

Special Characters in UNIX
Filenames cannot contain certain “special characters” Special meaning to the shell Examples & ; | * ? ‘ “ ` [ ] ( ) $ < > { } ^ # / \ see p. 38 in Sobell textbook for list

UNIX Wildcards Wildcards replace characters Example: ls ?h*e
* replaces zero, one or more characters ? replaces one character [ ] match one of the choices inside brackets { } match each of the choices inside braces Example: ls ?h*e Returns ah123e, bhe, 1h23e, etc. Example: ls t[aeiou1-3]p Returns tap, tep, tip, top, tup, t1p, t2p, t3p

Creating a Directory Type mkdir command at $ prompt
Example: mkdir reports Possible to create multiple directories with one command Use space as delimiter Example: mkdir memos letters

Clearing the Screen Use clear or cls command to clear screen
Clears screen buffer $ prompt only will appear at top of screen

More mkdir Command Options
mkdir -p cis14a/hw1 Creates cis14a directory as well as hw1 subdirectory below cis14a directory Use -p option to create multiple subdirectories at multiple levels at the same time Example: mkdir -p cis14a/hw2 cis14b

The rmdir and rm Commands
Use rmdir to remove a directory Current directory must be parent of directory to be deleted unless absolute or other relative path is specified If directory is not empty, use rm command rm -r hw1 for recursive remove rm -ir hw1 for interactive recursive remove System will prompt for confirmation

The cat and more Commands
cat [filename] Displays contents of file more [filename] Displays contents of file in segments Press Enter key to display one line at a time Press Spacebar to display one screen at a time Similar to pg [filename]

Ctrl Commands Ctrl-c interrupts current activity
Ctrl-u erases current command line Ctrl-w erases word in current command line Ctrl-s stops scrolling screen output Ctrl-q restarts scrolling screen output Other commands can be customized for user by administrator

The head and tail Commands
head [-n] filename Displays top portion of file head -5 hw1 displays first 5 lines of file hw1 tail [-n] filename Displays bottom portion of file tail -10 mbox displays last 10 lines of file mbox

UNIX Editors Use editor to create and edit files
Several editors available vi - most commonly used pico - not included in SVR4 Not available at CRC emacs - not included in SVR4

Visual Editor (vi) Type vi at $ prompt to start editor
vi [filename] to edit existing file (p. 212) Three modes (p. 183) Command mode Hit Esc key to access command mode Input (Text) mode Last-line mode ([shift]&[colon] keys)

Accessing vi’s Insert Mode
From command prompt, press i to insert text before cursor I to insert text at beginning of line a to append text after cursor A to append text at end of line o to open new line below cursor O to open new line above cursor Page 214

Accessing vi’s Last-Line Mode
From command mode, press : (colon) Necessary to save file and exit vi

vi Cursor Movements Command mode j or  moves cursor down one line
k or  moves cursor up one line l or  moves cursor to the right h or  moves cursor to the left Ctrl-D moves down one half screen Ctrl-U moves up one half screen Ctrl-F moves forward one screen Ctrl-B moves backward one screen

More vi Cursor Movements
Command mode w moves to next word $ moves to end of line G moves to last line Many more...

vi Commands dd - delete one line to buffer ndd - delete n lines
x - delete one character dw - delete one word to buffer d$ - delete to end of line to buffer d0 - delete to beginning of line to buffer

Command Mode u -- undo a last command/change . -- do last change again
Copy Text yy - yank a copy of a line to buffer nyy - yank a copy of n line to buffer yw - yank a copy of a word to buffer Past Text p -- put buffer after a cursor P -- put buffer before a cursor

Command Mode cw -- change a word ncw -- change n words
c$ -- change to end of a line r -- replace one character R -- replace the text (type over)

Last-Line Mode Commands
set showmode indicates Insert Mode or Command Mode At bottom right of screen set nu displays line numbers set nonu turns off line number display set list displays invisible characters set ic specifies that pattern search should ignore case

Searching File Contents
Access vi’s command mode /[string] finds next occurrence of string /^[string] searches for string at the beginning of a line /\>[string] searches for string at end of word More examples on p. 197 of textbook

Last - line Mode To turn off an option, put a “no” infront of the variable, i.e., set nu set nonu -- to turn it off Search for text /text -- go forward to the first occurence of text ?text -- go backward to previous occurence of test

Moving and Deleting Lines
:3,8d deletes lines 3 to 8 :4,9m 12 moves lines 4-9 to line 12 :2,5t 13 copies lines 2-5 to line 13 :5,9w filename writes lines 5-9 to filename

File Management Summary
Copying Renaming Moving

The cp Command Create an exact copy of another file
With the same name in a different directory Possible to specify target directory only With a different name in the same directory Syntax: cp [source] … [target] Example: cp misc ./w1/misc Copies file misc to subfolder w1 with the same name

More About the cp Command
Example: cp w2/* w4 Copies all files from w2 directory to w4 directory Does NOT copy subdirectories under w2 cp -r w2/* w4 also copies subdirectories Recursive Lowercase “R”!

Copying Multiple Files
Example: cp test test.out w3 Copies files test and test.out to w3 directory w3 directory must exist

The mv Command Moves and/or renames a file Example: mv test exam
Original file will disappear Different from cp command Example: mv test exam Renames file test to file exam Example: mv exam w4 Moves file exam to directory w4 w4 directory must exist mv command will not create it

Commands For Analyzing And Manipulating Files
sort - sort file contents grep - search file for a pattern diff - point out differences between files comm - details file differences wc - counts words, lines and letters in file compress - reduce file size to conserve disk space

The sort Command Sort information within files and/or merge different files Example: sort [filename] Sorts [filename] alphabetically by first word Example: sort -f +2 [filename] Sorts [filename] alphabetically by third word while ignoring case-sensitivity

The grep Command Global regular expression pattern
Find text patterns in files Syntax: grep [options] pattern [filelist] Example: grep echo test1 Finds pattern echo in file test1 and displays lines matching pattern

More grep Command Examples
Example: grep -c echo test1 Displays line count of lines matching pattern Example: grep -l echo Displays name of file that contains one or more matches

The diff Command Shows lines that are different between two files
Syntax: diff [filename1] [filename2] Example: diff t1 t2 Lists line and column number Lists different text patterns

The comm Command Displays line-by-line comparison of sorted files
Files must be sorted! Syntax: comm [filename] [filename] … Example: comm file1 file2 Results displayed in three columns file1 unique text patterns file2 unique text patterns common text patterns

The wc Command “Word Count” Display number of
Lines Words Characters Syntax: wc [options] [file-list] Example: wc -lw memo Displays the number of lines and words contained in the file memo

The compress Command Compresses files to reduce amount of space required on disk Similar to ZIP utility in DOS/Windows Compressed file cannot be viewed/executed until decompressed Syntax: compress [filename] Results in file filename.Z Example: compress -v text -v option displays compression ratio

Limiting Access to Resources
Use permissions Not available in DOS Usually available only on network operating systems (NOS) Who can change permissions? Owner of file or directory Administrator

Cis-14A: Misc Printing lp (after using script command)
File Transfer Protocol (FTP) Open Dos Command window ftp to log in Telnet Preference menu Name your file, and location start logging, do work, and stop logging Use word processor to print your file

Cis-14A: Misc Turn in assignments 1 and 2 File Structure Midterm 1
Tree structure Directory, and Files File names Extension Absolute and Relative Path cd, mkdir, rmdir, rm, cp, mv Midterm 1

File Structure Pyramid structure, inverted tree
Each directory -- a subject a folder can be divided into smaller directories for more clarity or easy to use sub-directory(ies) and/or file(s) the end of a path

File Structure File Name 14 chars, some has up to 255 chars A-Z, a-z
0 - 9 underscore (_) period (.) comma(,)

File Structure Filename Extension usually after period (filename.ext)
can use more than one period meaningful .ext, .c, .txt, Invisible Filename start with a period (.filename) ls -a

File Structure Absolute and Relative Paths
Commands that work with directory Change or go create, delete rename copy empty, or non-empty

File Structure Standard Unix Directories : / -- root
/home, /export/home /usr -- system information /usr/bin /usr/sbin /etc /var -- files that vary as system runs /tmp /dev

File Structure File or Directory Permission ls -l r read from the file
w write to the file x execute the file ls -l

File Structure chmod mode filename
who op permission File owner or root can change permission of a file

File Structure Symbolic Numberic chmod u+x,g+w,o+r r = 4 w = 2 x = 1

File Structure Links ln -- link command ln associate_file destination
hard link soft link ls -i

File Structure Question ???? BREAK

Redirection Standard Input Standard Output Redirect Output
cat > test cntl-d to end Redirect Input command [arg] < filename

Redirection Appending Use command >> Examples

Pipes command_a [arg] | command_b [arg] command_a > temp
command_b < temp rm temp Examples

Filter Processes an input stream of data to produce an output stream of data who | sort | lp who | tee test | grep user

Metacharacters * ? [,,,] {...}

UNIX/NFS Permissions NFS file permissions
Read (r) Write (w) Execute (x) Permissions listed in sequence of User Group World (all other users on system)

File Permissions vs. Directory Permissions
Permission File Directory Read r display/ list content copy Write w modify files add/delete Execute x execute control directory access

rw-r--r-- rwxr-xr-x File: Directory: Default Permissions
Default permissions after creation rw-r--r-- File: rwxr-xr-x Directory:

The chmod Command Change permissions Example: chmod u+w test
Syntax: chmod opcode filename Example: chmod u+w test Gives you permission to write to file test Does not influence existing permissions Example: chmod g+r test Gives your group permission to read file test

chmod Permission Categories
u - user g - group o - others (world) a - all

Taking Permissions Away
chmod g-x Takes execute permission away from group Does not change r and w permissions

Absolute Permissions chmod o=x Example: chmod a=x test
Assigns execute permission to others Example: chmod a=x test Sets permissions to execute ONLY r and w permissions are eliminated

Setting Permissions Using Symbolic vs. Numeric Mode
Symbolic mode rwx rwx rwx Example: chmod u+r test Numeric mode Example: chmod 700 text Possible to set absolute permissions only

Redirecting Screen Output
Prevent output from echoing to screen Is sent to file/printer instead Example: ls > test.out Sends ls listing to file test.out Caution: Existing file will be overwritten without warning! Use >> option to append existing file Example: ls >> test.out

Capturing Keystrokes Record keystrokes Use cat command
Syntax: cat > filename Type text to capture to file Press Ctrl-D to stop capturing and write to specified file Example: cat > test.out

Piping Use the | (pipe) character
Modifies or redirects previous command in line Example: man ls | more Displays help for the ls command one screenful at a time Example: who | sort | lp Sends a sorted list of currently logged-in users to the printer Note: lp command must be last command

Communicating in UNIX Real-time communication E-mail communication
write talk communication mailx

The write Command Send instant message to other user on UNIX system
Similar to “chatting” Recipient must permit messaging Type mesg y at $ prompt Example: write geisslm Opens write session with user geisslm End conversation with “oo” (over and out) Press Ctrl-C to end transmission

The talk Command Similar to write command
Divides user screen into two windows Statements displayed in opposite window on other end of communication My “talking” appears here Your “talking” appears here

The mailx Command Send electronic mail from UNIX system
Syntax: mailx [username] Type subject line Type message Press Ctrl-D to send message Example: mailx geisslm Type subject line and message Example: mailx geisslm < message.fil Sends file message.fil to user geisslm

Using mailx Interactively
Many options available Type ? at ? prompt to view list of available options Example: t 2 Types second message on screen Example: delete 3 (or d 3) Deletes message number 3 from message list Example: h Displays list of message headers

Mail Message Listing Message type Sender Date and time Size Subject
N - new message R - read message O - old message Sender Date and time Size Subject

Changing Message Options
Possible to change options while typing message text Use ~ (tilde) character options Be sure to specify option after issuing command Otherwise information may be missing Specify in mailx command line mailx -s “ test” geisslm < test.doc Sends file test.doc to user geisslm with subject “ test”

More About mailx Replying
r replies to all recipients of original message R replies to sender of message ONLY

Exiting mailx Input Mode
quit command processes messages exit command leaves mailbox “untouched”

Aliasing Alias For one username For multiple usernames
Distribution list Example: alias entry in .mailrc file .mailrc is UNIX customization file Entry: alias users user1 user2 Mail sent to alias users is forwarded to user1 and user2 Create current-session alias at $ prompt

Alias Advantages Issue multiple commands through one alias
Example: alias home=‘clear;cd;pwd;ls’ Clears the screen, changes to home directory, displays current directory and its contents “Rename” UNIX commands to DOS commands Example: alias dir=‘ls -l’ Possible to issue DOS-like dir command to view contents of current directory

Removing Aliases Use unalias command to remove alias(es)
Example: unalias test Removes test alias in current session

That’s All, Folks! Course Review Final Exam

CIS 14A - Operating Systems (UNIX)

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