Basic UNIXWelcome to Basic Unix (Part 1) brought to you by MYEC
& PDC DA
SyllabusPart 1 What is UNIX? Your first UNIX Session The UNIX
File System Data Streams More Commands The Shells UNIX Security
Policy vi Editor Part 2 Multi-Tasking System Management Devices
E-mail Networking X-Windows NetBatch & CSD Revision Control
What is UNIX?
UNIX is an operating system that is:Interactive (not batch)
Multiprocess Threaded (multi-processor) Multi-user Multi-purpose
Open source Secure Networked Portable (Linux Laptop)
Today UNIX interfaces with Windows and shares files through
software like Samba, VNC, & Exceed.
The KernelKernel Drivers
Hardware
The heart of any operating system is the hardware.
The Shell, File Systems, UtilitiesThe Shell -command
interpreter
File System
Kernel
Network
Utilities
Major UNIX concepts
Hierarchical file system Data Streams: STDIN, STDOUT, STDERR,
pipes, redirection, filter Shell sh, csh, Security login, passwd,
permissions, groups Built-in mail system Network File System (NFS)
Network Information System (NIS/YP) Domain Name System (DNS)
X-windows
Quiz
What is UNIX ? What does UNIX use to control the hardware ?
Your first UNIX Session
Logging In
Login into a workstation, computer server, via: telnet, rlogin,
rsh, ssh Enter username & password at login prompt Username
will be visible Password will NOT be visible
Login Examples% % % % % telnet pgli0003 rlogin pglw8019 rsh
pghc0002 rsh insite.fm.intel.com -l ewee ssh
insite.fm.intel.com
Remote Access
rlogin l kyeoh3 pglc8010
Establishes a remote connection from your terminal to a remote
machine
rsh pglc8010 touch file1
Runs a shell-level non-interactive command on another
computer
ssh pglc8010
A substitute for rsh is called ssh; which encrypts all
information between the SSH client and server
xhost +
Allows GUI display from remote UNIX systems
setenv DISPLAY pglw8010.png:2
Bring up X Windows
Most UNIX workstations are not with GUI Use runx command to
bring up the X windows Windows managers: fvwm2, fvwm95, twm,
Default windows manager MYEC provides is fvwm2 fvwm2 environment
startup file is $HOME/.fvwm2rc
Change password
Change your password at your first login after you received your
account though mail or voicemail. If you havent, do it NOW. Make
your UNIX password strong with 6 to 8 characters which combine with
alpha-numeric + special characters ($ % ^ @ # ; : > who
| wc -l
who
STDIN STDOUT STDERR
STDIN STDOUT STDERR
wc -l
Redirection with the concept of pipe, you can redirect your data
output to a file or devicewho who > file1 ls l file1 cat file1
wc l < file1 date >> file1
% % % % % %
You can redirect error to a file
% wc file1 >& err.file % cat err.file
Quiz
What are those 3 data streams in standard shell ? How do you get
the data into a file ? How do you link a commands output to another
commands input ?
FiltersBeside pipes, redirections, you can modify your data
output with filters
grep sed awk sort
grep
% ps ef | grep sh % ps ef | grep
grep flags
dont want this (filter out) -i neglect lower/upper case -n give
line numbers -c count lines-v
sed
sed is Single-line EDitor, it processes data line-by-
line
% cat /etc/passwd | sed s/bin/BIN/ % cat /etc/passwd | sed n
1,2s/bash/BASH/ % cat /etc/passwd | sed n 1,2s/bash/BASH/p
sed flags-n
silent mode
awk
awk is a pattern matching for filtering data
% cat /etc/passwd | grep root % cat /etc/passwd | grep root |
awk F: {print $6} % cat /etc/passwd | awk F: {print $1}
awk flags -F field delimiter
sort
Sometimes you will need to sort your data outputsort flags
% cat /etc/passwd | awk F: {print $1} | sort
-d dictionary order-n numeric -r reverse
-u unique (no repeat occurance)
Quiz
What do these commands do: grep, awk, sort ?
Lab
Run the command ypcat hosts | grep pglw and put the sorted
second column of the output into a file: linux.ws List all the
users logged in and sort them into a file, and display number of
users logged in at the last line of the file
More Commands
Some Productive Hints
man, date, hostname, w, whoami, history, !
Wild cards
* ? []
any character(s) one, and only one character a range of
characters [0-9] [A-z]
Comparing Files
cmp diff sdiff tkdiff
Hard & Soft Links
ln Hard link Creates a new item, newlink which changes with
oldfile rm resistant, non-nfs friendly, non-directory friendly ln s
Soft (symbolic) link Creates a new pointer (ala Windows
shortcut)
Compressing Files
.gz
gzip / gunzip
Smallest size!
.Z
compress / uncompress
.zip
zip / unzip
tar
tar Tape Archive Restore
Example: Copying file% tar cf
Extract files% tar xvf
View contents of .tar file% tar tvf
Process Table
/usr/bin/ps -wef /usr/ucb/ps auwx kill -9
ps flags
ps ef
ps ax
System V, AIX, HPUX, Linux BSD, SunOS
Lab 4
cd to your home directory
Redirect man page of true to a file true.f Redirect man page of
test to test.f Make a directory called lab cd to lab touch 3 files:
a, b, c. List them all with l Remove a. List them again with l
Remove lab
The Shells
The Shell
UNIX shells are command interpreter and a programming language,
usually used by admin for automated operations There are more than
one shell in UNIX world sh borne shell, most machines roots shell
csh C shell, a favorite for most users, ECs default shell tcsh an
enhanced C shell .cshrc your C shell environment file .login your C
shell login setting file .aliases this is where you customize your
shortcut keys
Shell Environment
env
Common Environment variables:
TERM terminal types HOME home directory PATH - your search path
for commands PROMPT your system prompt TZ time zone EDITOR default
editor DISPLAY the display location of X UID your user ID GID your
group ID
Set Values to Variables
In csh / tcsh:% % % % % % % set hi = Hello set there = world
echo $hi $there set unset hi there echo $hi $there setenv DISPLAY
`hostname`:0.0
Quiz
How to see your environmental variable? Where is $HOME first
set? What kind of variables are these:
HOME, PATH, TERM
Lab
Set a, b, c & d to 1-4 Display their values Unset them
Shell Quotes
used to preserve white space characters string ` ` runs command
within the shell
Useful Shell Prompt
Put the following alias into your ~/.aliases, change the prompt
if necessary:
alias cd 'cd \!*; set prompt = "%m:`pwd` %# "'
To use it:
source ~/.aliases
Simple Shell Script example#!/bin/sh a=3 b=4 c=`expr $a + $b`
echo $a + $b = $c
Looping
whilewhile 1 $ date $ sleep 1 $ end
foreachforeach x ( a b c) $ echo $x $ end foreach x (`env`) $
echo $x $ sleep 1 $ end
n=1 while {$n -ne 10} do echo $n n=`expr n+1` done
Lab
Create a loop routine to count down 10, 91 Use your knowledge of
common Unix commands and utilities (filter, pipe, etc) to create 2
files: linux.ws.alive, linux.ws.deadlinux.ws.alive - all Linux
workstation alive using ping command linux.ws.dead all linux
workstation not responding using ping command
More on tcsh
tcsh being one of the more popular shells FeaturesSimple command
cycling/editing Filename/Command completion
tcsh Shortcut Summary
Command History in tcsh
!!
Repeats previous command. !!:p Prints out the previous command.
!-2 Repeats second-to-previous command. !-2:p Prints
second-to-previous command. !23 Repeats command 23 as specified in
the history list. !cat Repeats the most recent command that started
with cat. !?cat Repeats the most recent command that had cat in it.
!$ use the last word from the previous command and substitute it
for this command !* use all words except the first one from the
previous command and substitute them for the command.
history Lists out the previous commands in a format like: 86
9:26 cd admin 87 9:26 ls status/ 88 9:26 cd .. 89 9:26 ls tmp/
Quiz
1) 2)
3)4)
You have been entering a bunch of commands, and several commands
earlier was a very long one that you need to enter again. Name at
least four ways to enter this command: Type it in completely
Answers1) 2) history, then ! 3) ! 4) arrow-keys
UNIX Security Policy
File/Directory Access Permission
drwxrwxrwxTypeOwner Group Others
Types: file d directory l link b binary
Access Permission: r readable w writable x executable reverse of
rwx
Examples
drwxrwxrwx World read/writeable directory -rwxrwxrwx World
read/writeable file -r-xr-xr-x Executable only
-rwxr-xr-x Executable, owner writeable-rwxrwx--- Executable,
owner & group
writeable, others unreadable -rwxr-x--- Quiz
Modify File/Directory Permission
chmod u+?-?,g+?-?,o+?-? file1 chmod ### file1 Example:
chmod u+rwx,g+rx-w,o+rx-w file1 chmod 755 file1
File/Directory Ownership
chown chgrp chown ##:## (productivity of csh) groups gid
Creation mask setting
The umask command sets or displays the creation mask setting
which defines default attributes for new files Settings are the
complement of chmod
umask 022 -rw-r- - r - umask 027 -rw-r- - - - -
Sticky bit
sticky bit only works on directories It is to make sure all
files inside the directory having same GID
drwxrwsrwx 5 sys sys 543 May 9 09:41 etc
Lab
touch a new empty file: file2
Check its default permission and ownership Change its permission
to rwxr-x--Change its GID to PDC Change its ownership to root. Can
you?
General UNIX Security Guideline
Login access
rule-based password protection passwords have 3-month shelf life
Protect .rhosts with 0600
Network access
File/Directory protection Command search path - $PATH
Keyboard/Screen access permission
xlock
PDC Security Guideline
UNIX security has to comply with Intels information security
policies & guidelines. Non-compliance of UNIX security will put
Intel in danger of losing Intellectual Property.
PDC UNIX Security Guideline (cont)
File permission guidelines
First level, external users cannot access Intel file systems.
Second level, you can protect your files from other Intel users.
For example, no one else should be able to read your mail since
mail is private. Project databases and some other material are
sensitive and are accessible only to some users. Keep your home
directory non-group writable. No one should be allowed to write in
your area. When working in project areas, make your files group
writable if they are shared.
vi Editor
vi
UNIX users favorite editor - a headache to Windows users You can
use for a text file:
Viewing Inserting Appending Deleting Moving Copying Going to
shell from within vi
Modes within vi
command mode
h left, j down, k up, l right x erase character dd delete line,
10dd yy yank or copy, y1 p - paste u - undo . repeat the last vi
command (favorite productivity) 0 move to beginning of line
cw change a word r replace a character / - initiate a search n
search next pattern J merge lines G go to bottom of lines :# - go
to line # :r read a file from shell :set nu, :set nonu set/unset
line # ^F page down (forward) ^B page up (backward) :wq, :wq! -
write & quit
input mode, to exit
i insert, I insert at the begin of line a append, A append at
the end of line o open a new line, or append at the next line
Lab
