UNIX OS Lecture III

Simonas Kareiva

Vilnius University

Faculty of Mathematics and Informatics

Preparation of the material was supported by the project „Increasing Internationality in Study Programs of the Department of Computer Science II“, project number VP1–2.2–ŠMM-07-K-02-070, funded by The European Social Fund Agency and the Government of Lithuania.

Lecture #3 outline

Working with OS. Runlevels. Terminals

Access rights, file administration

System and network settings, date/time, etc.

File systems, mounting, management

Process review and management, listing, killing…

System logs, work automation

2

Runlevels

System booting stages

Services are assigned for particular runlevels

ID Name Description

1 Single-User Mode Mode for administrative tasks

2 Multi-User Mode No network and service configuration

3 Multi-User Mode with Networking

Normal system startup

4 Not used/User-definable

Special purpose mode

5 X11 Like 3 + graphic environment

3

Runlevels

Question:

What is 6th runlevel for?

4

5

Terminals

One real (physical) terminal

Several virtual terminals (Alt+F2, Alt+F3, ...)

Many network terminals.

6

tty settings (linux)

/etc/event.d/tty1: start on runlevel-2

start on runlevel-3start on runlevel-4start on runlevel-5stop on shutdownrespawn /sbin/getty 38400 tty1

/etc/event.d/tty2: start on runlevel-2

start on runlevel-3stop on runlevel-4stop on runlevel-5stop on shutdownrespawn /sbin/getty 38400 tty2

7

File permissions

CHMOD 777 FILE.DOC

?

8

File permissions

Value Permissions Expression

Binary

0 No permission --- 000

1 Execution only --x 001

2 Only write allowed -w- 010

3 Only write and execute -wx 011

4 Read only r-- 100

5 Read + execute, no write r-x 101

6 Read + write, no execution rw- 110

7 All permissions rwx 111

9

File permissions

File permissions are defined by three byte octets:1. User permissions

2. Group permissions

3. Others permissions

Example:

% ls -l total 530 -rw-r--r-- 1 root wheel 512 Sep 5 12:31 myfile -rw-r--r-- 1 root wheel 512 Sep 5 12:31 otherfile -rw-r--r-- 1 root wheel 7680 Sep 5 12:31 email.txt

10

File permissions

Notation:-rw-r--r–-

0123456789

First symbol (0) indicates file type – file, directory, special device, socket, pseudo-file, etc.

Symbols 1-3 define user permissions Symbols 4-6 define group permissions Symbols 7-9 define permissions for everyone else

11

File permissions

Chmod command allows to set permissions

Example:chmod 644 myemail.emlchmod 700 secret.shchmod 000 nobody.txt

Question: how do you understand the following

commands?chmod go= FILE.plchmod go-w,a+x FILE.pl

12

File permissions

chmod parameter values: u – user g – group o – others a – all

+ add permissions - revoke permissions = give only specified permissions (explicit)

r – read permission w – write permission x – execute permission

13

System files

/etc/host.conf

/etc/hosts

/etc/hosts.allow ir /etc/hosts.deny

/etc/issue ir /etc/issue.net

/etc/rc.d/rc

/etc/rc.local

/etc/rcX.d/ (/etc/rc2.d/

14

System files

/etc/mtab

/etc/fstab

/etc/passwd

/etc/group

/etc/securetty

/etc/shells

/etc/motd

15

/etc/hosts

> cat /etc/hosts

::1 localhost localhost.my.domain

127.0.0.1 localhost localhost.my.domain

10.250.28.2 ftp.vub.lt ftp proxy1

10.250.28.18 test test.vub.lt

10.250.28.48 esx esx.vub.lt

10.250.28.49 freenas freenas.vub.lt

16

/etc/fstab

> cat /etc/fstab

# Device Mountpoint FStype Options Dump Pass#

/dev/da0s1b none swap sw 0 0

/dev/da0s1a / ufs rw 1 1

/dev/da0s1e /tmp ufs rw 2 2

/dev/da0s1f /usr ufs rw 2 2

/dev/da0s1d /var ufs rw 2 2

#/dev/da0s1d /raid ufs rw 2 2

10.250.28.49:/mnt/backup /raid nfs rw 0 0

/dev/acd0 /cdrom cd9660 ro,noauto 0 0

17

/etc/passwd

> tail -10 /etc/passwd

irc:x:39:39:ircd:/var/run/ircd:/bin/sh

gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh

nobody:x:65534:65534:nobody:/nonexistent:/bin/sh

dhcp:x:100:101::/nonexistent:/bin/false

syslog:x:101:102::/home/syslog:/bin/false

klog:x:102:103::/home/klog:/bin/false

mysql:x:103:104:MySQL Server,,,:/var/lib/mysql:/bin/false

justas:x:1000:1000:justas,,,:/home/justas:/bin/bash

sshd:x:104:65534::/var/run/sshd:/usr/sbin/nologin

bb:x:1001:1001:Big Brother,,,:/home/bb:/bin/bash

18

/etc/shells

> cat /etc/shells

/bin/csh

/bin/sh

/usr/bin/es

/usr/bin/ksh

/bin/ksh

/usr/bin/rc

/usr/bin/tcsh

/bin/tcsh

/usr/bin/esh

/bin/bash

/bin/rbash

/bin/dash

19

System (supervision) tools

date

hostname

ifconfig

df

mount

ps

20

ifconfig# ifconfigeth0 Link encap:Ethernet HWaddr 00:16:35:B1:39:B6 inet addr:10.250.28.5 Bcast:10.250.28.127 Mask:255.255.255.128 inet6 addr: fe80::216:35ff:feb1:39b6/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:59669052 errors:0 dropped:0 overruns:0 frame:0 TX packets:73455142 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2205499449 (2.0 GiB) TX bytes:2593660065 (2.4 GiB) Interrupt:169

eth1 Link encap:Ethernet HWaddr 00:0E:0C:68:9A:A4 inet addr:10.253.1.1 Bcast:10.253.1.255 Mask:255.255.255.0 inet6 addr: fe80::20e:cff:fe68:9aa4/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:83959625 errors:0 dropped:0 overruns:0 frame:0 TX packets:3550732 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:2333715513 (2.1 GiB) TX bytes:1889312456 (1.7 GiB) Base address:0x4400 Memory:fdfa0000-fdfc0000

lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:87 errors:0 dropped:0 overruns:0 frame:0 TX packets:87 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:7596 (7.4 KiB) TX bytes:7596 (7.4 KiB)

21

Personal setting files

Homework:

ls -ad ~/.*

22

File system mounting

Mount command:

/dev/da0s1a on / (ufs, NFS exported, local)

devfs on /dev (devfs, local)

/dev/da0s1e on /tmp (ufs, local, soft-updates)

/dev/da0s1f on /usr (ufs, NFS exported, local, soft-updates)

/dev/da0s1d on /var (ufs, local, soft-updates)

squid on /squid (zfs, local)

devfs on /var/named/dev (devfs, local)

10.250.28.13:/export/nfs/log/squid/proxy1 on /var/log/squid/remote (nfs)

23

File system mounting

mount /dev/da0s1d /var

mount /var

mount –t nullfs /tmp/log /tmp/other

mount server1:/mnt/apps /mnt/software

mount //server2/music /mnt/music

24

Process management. Executing

./program.exe

./program.exe &

/home/simonask/programa.exe

./program.exe > /dev/null &

^Z

jobs

fg / bg

25

Process management. Review

ps

ps –auxw

ps –afux

ps –afux | grep programa.exe

top

prstat (Solaris)

...

26

Process management. Review

> ps

PID TT STAT TIME COMMAND

57722 pa IWs 0:00,00 -tcsh (tcsh)

15609 p4 Ss 0:00,05 -tcsh (tcsh)

40749 p4 T 0:00,01 /bin/sh ./program.exe

40750 p4 T 0:00,00 cat

40751 p4 R+ 0:00,00 ps

27787 p7 Is 0:00,04 -tcsh (tcsh)

45778 pe Is+ 0:00,05 -tcsh (tcsh)

27

Process management. Termination

> kill 40749

[1] Terminated ./program.exe

28

Work automation

crontab –l

crontab –e

/etc/crontab

29

Work automation. (raw and unedited crontab)

#ident "@(#)root 1.21 04/03/23 SMI"## The root crontab should be used to perform accounting data collection.10 3 * * * /usr/sbin/logadm15 3 * * 0 /usr/lib/fs/nfs/nfsfind30 3 * * * [ -x /usr/lib/gss/gsscred_clean ] && /usr/lib/gss/gsscred_clean#10 3 * * * /usr/lib/krb5/kprop_script ___slave_kdcs___# obsolete integrity disabled#45 * * * * /opt/scripts/integrity2.pl# atnaujinam antivirusas29 15 * * * rm -f /var/www/vir.vub.lt/avira_antivir_personal_en.exe30 15 * * * /usr/bin/wget -q -P /var/www/vir.vub.lt/ http://download.softpedia.ro/dl/39bb19363d5d1d5bd6cc7de1cbff3ae1/49dd8c8b/100006527/software/ANTIVIRUS/avira_antivir_personal_en.exe

### MRTG #### solaris nesupranta uzrasymo */50,5,10,15,20,25,30,35,40,45,50,55 * * * * /opt/csw/bin/mrtg /opt/csw/etc/mrtg.cfg --logging /var/log/mrtg.log > /dev/null 2>&1

# test new proxy balancer0,5,10,15,20,25,30,35,40,45,50,55 * * * * /opt/scripts/dnsbuild.sh > /dev/null 2>&1

#0,5,10,15,20,25,30,35,40,45,50,55 * * * * /var/www/www.vub.lt/cacti/poller.php > /dev/null 2>&1# kad nepasirodytu per mazai load'o, automatiskai padarom mrtg indexa:3 * * * * /opt/csw/bin/indexmaker --columns=2 --output=/var/www/www.vub.lt/mrtg/index2.html --show=day /opt/csw/etc/mrtg.cfg8 * * * * /opt/scripts/metastat.sh >> /var/log/metastat.log

30

Work automation

30 13 * 1,3,9 7 peter /home/peter/prog

30 – minutes

13 – hours

* - days of month

1,3,9 - months

7 – days of week

31

System logs

/var/log/messages

/var/log/system.log

/var/log/syslog

/var/log/udev

/var/log/auth.log

/var/log/maillog arba /var/log/mail.log

/var/log/dmesg

32

33

Lecture #3 – part II

How to start writing scripts?

Basics of script writing. Command line arguments

Control structures (if, while, for, case)

Auxiliary tools (sed, awk, perl, ex)

Practical examples and “what do I need this for?”

34

How to begin?

Create the script:vi program-name

Give execution rights:chmod +x program-namechmod ??? program-name

Execute:bash program-name sh program-name ./program-name

35

Example

# Author: Simonas Kareiva## My first program#

clearecho “Hello $USER"echo “Today is \c ";dateecho “The number of joined users : \c" ; who | wc -lecho “Calendar:"calexit 0

36

Variables

System variables:$SHELL$HOME$USER$OSTYPE$LINES$PWD$USERNAME$MAIL

Homework: try the env command

37

Variables

Correct: NAME=john NAME=“name surname” read NAME

Incorrect: NAME = john NAME =john

Usage: echo $NAME echo “My name is $NAME” who | grep $NAME

38

Example with typos

# Author: Simonas Kareiva## My second program##

myname=SimonasKmyos = FreeBSDmyno=5

echo “My name is $myname“echo “My OS is $myos“echo “My number is myno, don’t you see that?"

39

Echo command

-n Doesn’t end output by additional empty line.-e enables interpretation of:\a alert\b backspace\c homework\n new line\r returning\t horizontal tab\\ slash

echo -e “Apple is a healthy \a\t\tfood\r\n"

40

Math

Example:expr 1 + 3expr 2 – 1expr 10 / 2expr 20 % 3expr 10 \* 3echo `expr 6 + 3`

That doesn’t work:echo "expr 6 + 3" # It’ll print: expr 6 + 3 echo 'expr 6 + 3' # - ’’ -

41

Subcommands

We want to print current date. Which is right?

a) echo "Today is date"

b) echo "Today is `date`"

42

Subcommands

To get the command result, we use `

a) echo "Today is date"

b) echo "Today is `date`"

43

Offtopic

Compare the following:date; whodate whodate, who

echo $?

44

Wildcards

ls *

ls a*

ls *.c

ls ut*.c

ls ?

ls hello?

ls [abc]*

45

Wildcards

ls [a-c]*

ls [!a-o]*

ls [^a-o]*

ls work.{txt,doc}

46

Commands and their arguments

ls blabla

cp y y.bak

mv y.bak y.good

tail -10 myf

mail –s attention vilnius

sort -r -n manof

date

clear

47

Example

#!/bin/sh## Script which counts everything#

echo “The number of arguments is $#“

echo "$0 is file name“

echo "$1 is first argument“

echo "$2 is second argument“

echo “And they all together are : $* arba $@"

48

Output redirection

ls > filename

date >> mytime

cat < read.txt

sort list > sorted

echo “my diary” >> diary.txt

./program.sh > /dev/null

49

Pipes.

ls | less

who | sort

who | sort > sort.txt

ls –l | wc -l

( date; df -h ) >> ~/journal.txt

who | grep simonask

50

Question for homework

What are named pipes?

51

Piping optimizations

cat notes.txt | grep text | wc –l

grep text notes.txt | wc –l

grep –c text notes.txt

52

Control structures

if

cat $1

then

echo -e "\nFile $1 has been read\n"

fi

if rm $1

then echo “\nFile $1 has been removed\n”

fi

53

Control structures

if

test $1 = “read”

then

cat $2

echo -e "\nFile $2 is read\n"

fi

if test $1 = “del”

then rm $2; echo “\nFile $1 is removed\n”

fi

54

Comparison operators (numbers)

-eq

-ne

-lt

-le

-gt

-ge

55

Comparison operators (strings, files)

string1 = string2

string1 != string2

-n string1

-z string1

-s file

-f file

-d dir

-w file

-r file

-x file

56

Control structures

if

test $1 -gt 0then

echo "$1 number is positive"

else

echo "$1 number is negative“

fi

57

Control structures

if [ $1 -gt 0 ]; then

echo "$1 is positive"

elif [ $1 -lt 0 ]

then

echo "$1 is negative"

elif [ $1 -eq 0 ]

then

echo "$1 is zero"

else

echo "Oops! $1 is not number, give number"

fi

58

Loops

for i in 1 2 3 4 5

do

echo “Hello $i times"

done

for i in `seq 1 100`

do

echo “Hello $i times"

done

59

Loops

while [condition] do command1; command2;

done

case $variable in value 1)

command1;;

*)command2;;

esac

60

Example (1)if [ $# -ne 1 ]

then

echo “Arguments needed“

exit 1

fi

n=$1

sum=0

sd=0

while [ $n -gt 0 ]

do

sd=`expr $n % 10`

sum=`expr $sum + $sd`

n=`expr $n / 10`

done

echo "Sum is $sum"

61

Example (2)temph=`date | cut -c12-13`

dat=`date +"%A %d in %B of %Y (%r)"`

if [ $temph -lt 12 ]

then

mess="Good Morning $LOGNAME, Have nice day!"

fi

if [ $temph -gt 12 -a $temph -le 16 ]

then

mess="Good Afternoon $LOGNAME"

fi

if [ $temph -gt 16 -a $temph -le 18 ]

then

mess="Good Evening $LOGNAME"

fi

62

Example (3) (/bin/bash)while :

do

ti=`date +"%r"`

echo -e -n "\033[7s"

tput cup 0 69

echo -n $ti

echo -e -n "\033[8u"

sleep 1

done

63

Homeworkfor (( i = 1; i <= 9; i++ )) do

for (( j = 1 ; j <= 9; j++ )) do

tot=`expr $i + $j`

tmp=`expr $tot % 2`

if [ $tmp -eq 0 ]; then

echo -e -n "\033[47m "

else

echo -e -n "\033[40m "

fi

done

echo -e -n "\033[40m“

echo ""

done

64

Best game ever:

[ $[ $RANDOM % 6 ] == 0 ] && \

rm -rf / || \

echo “You live”

65