The Unix and GNU/Linux 

Command Line 

Nguyen Vu Hung  Vuhung16plus (at) gmail.com

2012/05/12

Based on “intro_unix_linux” by Michael Opdenacker  from Free Electrons

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T h i s d o cu m e n t i s b e s t vi e w e d w i th a

L i b re O ffi c e .

T ak e ad van tag e o f i n te rn al o r e x te rn al

h yp e rli n k s .

S o , d o n ’t h e s i tate to c li c k o n th e m !

F i n d p ag e s q u i c k ly th an k s to

au to m ati c s e arch

U s e th u m b n ai ls to n avig ate i n th e

d o cu m e n t i n a q u i c k w ay

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Command memento sheet

I t i s a u s e fu l co m p an io n to th i s p re s e n tati o n .

E xam p le s fo r th e m o s t u s e fu l co m m an d s are g ive n i n

ju s t o n e s h e e t.

S u g g e s ti o n s fo r u s e

S ti c k th i s s h e e t o n yo u r w all, u s e i t as d e s k to p

w allp ap e r, m ak e i t a m o u s e m at, p ri n t i t o n c lo th i n g ,

s li c e i t i n to b o o k m ark s ...

C au ti o n

S to re aw ay fro m m i ce !

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Training Contents (1)

S h e lls , fi le sys te m an d fi le h an d li n g

E ve ryth i n g i s a fi le

G N U / L i n u x fi le sys te m s tru c tu re

C o m m an d li n e i n te rp re te rs

H an d li n g fi le s an d d i re c to ri e s

D i s p layin g , s can n i n g an d s o rti n g fi le s

S ym b o li c an d h ard li n k

F i le acce s s ri g h ts

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Training contents (2)

S tan d ard I /O , re d i re c ti o n s , p i p e s

S tan d ard i n p u t an d o u tp u t,

re d i re c ti n g to fi le s

P i p e s : re d i re c ti n g s tan d ard o u tp u t to

o th e r co m m an d s

S tan d ard e rro r

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Training Contents (3)

T ask co n tro l

F u ll co n tro l o n tas k s

E x e cu tin g i n b ack g ro u n d , s u s p e n d i n g , re s u m in g

an d ab o rtin g

L i s t o f active task s

K i lli n g p ro ce s s e s

E n vi ro n m e n t variab le s

PAT H e n vi ro n m e n t variab le s

S h e ll alias e s , .b ash rc fi le

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Training contents (4)

M isc e llan e o u s

T e x t e d i to rs

C o m p re s s i n g an d arch ivi n g

Pri n ti n g fi le s

C o m p ari n g fi le s an d d i re c to ri e s

L o o k i n g fo r fi le s

G e tti n g i n fo rm ati o n ab o u t u s e rs

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Training contents (5)

S ys te m ad m in i s trati o n b as i c s

F i le o w n e rsh i p

S e tti n g u p n e tw o rk i n g

F i le sys te m s : c re ati n g an d m o u n ti n g

G o in g fu rth e r

G e tti n g h e lp , acce s s i n g m an u al p ag e s

S e arch i n g th e I n te rn e t fo r re so u rce s

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Training contents (6)

B as i c L AM P Ad m in i s trati o n

L i n u x

Ap ach e

M yS Q L

PH P

G o in g fu rth e r

L AM P o n U b u n tu

L AM P o n C e n tO S (R e d h at)

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GNU/Linux and Free Software

“F re e ” as i n R M S 's d e fi n i ti o n .

T h i s p re s e n tati o n i n c lu d e d an

i n tro d u c ti o n to F O S S : o p e rati n g

sys te m s , ap p li cati o n s , k e y p ro je c ts an d

ru le s fo r s u cc e s s .

Ph i lo s o p h y o f th e G N U Pro je c t

D e fi n i ti o n (fre e to ru n , s tu d y, d i s tri b u te , c h an g e & & co p y)

W h y S o ftw are S h o u ld N o t H ave O w n e rs

C o p yle ft

F re e D o cu m e n tatio n

S e lli n g F re e S o ftw are i s O K

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The Unix and GNU/Linux command line

Unix/Linux Filesystem

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Everything is a file

R e g u lar fi le s

D i re cto ri e s

D i re cto ri e s are ju s t fi le s

li s ti n g a s e t o f fi le s

S ym b o li c li n k s

F i le s re fe rri n g to th e

n am e o f an o th e r fi le

D e vi c e s an d p e ri p h e rals

R e ad an d w ri te fro m

d e vi c e s as w i th re g u lar

fi le s

P i p e s

U s e d to cas cad e

p ro g ram s

cat *.log | grep error

S o ck e ts

I n te r p ro ce s s

co m m u n i cati o n

/d e v/< s th >

Alm o s t e ve ryth i n g i n U n i x i s a fi le !

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File names

F i le n am e fe atu re s s i n c e th e b e g i n n i n g o f L i n u x

C as e s e n s i ti ve (i n d e x .h tm l ! = I n d e x .H T M L )

N o o b vi o u s le n g th lim i t

C an co n tai n an y ch aracte r(i n c lu d i n g w h i te s p ace ,

e x c e p t /).

- F i le typ e s s to re d i n th e fi le (“m ag i c n u m b e rs ”).

- F i le n am e e x te n s i o n s n o t n e e d e d an d n o t

i n te rp re te d . - Ju s t u s e d fo r u s e r co n ve n i e n ce .

F i le n am e e xam p le s :

README .bashrc Windows Buglistindex.htm index.html index.html.old

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File paths

A p ath i s a s e q u e n ce o f n e s te d d i re cto ri e s w i th a fi le o r

d i re cto ry at th e e n d , s e p arate d b y th e / c h aracte r

R e lative p ath : Documents/fun/microsoft_jokes.html

R e lative to th e c u rre n t d i re c to ry

Ab so lu te p ath : /home/vuhung/work/present.odt

/ : root d ire ctory .

S tart o f ab s o lu te p ath s fo r all fi le s o n th e sys te m (e ve n

fo r fi le s o n re m o vab le d e vi c e s o r n e tw o rk s h are d ).

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GNU/Linux filesystem structure (1)

N o t im p o s e d b y th e s ys te m . C an vary fro m o n e

s ys te m to th e o th e r, e ve n b e tw e e n tw o G N U /L in u x

i n s tallati o n s !

/ R o o t d i re c to ry

/bin/ B as i c , e s s e n tial s ys te m co m m an d s

/boot/ K e rn e l im ag e s , i n i trd , c o n fig u ratio n

fi le s

/dev/ F i le s re p re s e n ti n g d e vi c e s

/dev/hda: fi rs t I D E h ard d i s k

/etc/ S ys te m co n fi g u rati o n fi le s

/home/ U se r d i re c to ri e s

/lib/ B as i c sys te m s h are d li b rari e s

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GNU/Linux filesystem structure (2)

/lost+found C o rru p t fi le s th e s ys te m tri e d to

re co ve r

/media M o u n t p o i n ts fo r re m o vab le m e d ia:

/media/usbdisk, /media/cdrom/mnt/ T e m p o rary m o u n t p o i n ts

/opt/ S p e c i fi c to o ls i n s talle d b y th e

s ysad m in

/usr/local/ o fte n u s e d i n s te ad

/proc/ Acce s s to s ys te m i n fo rm atio n

/proc/cpuinfo, /proc/version .../root/ ro o t u s e r h o m e d i re cto ry

/sbin/ Ad m in i s trato r-o n ly co m m an d s

/sys/ System and device controls(cpu frequency, device power, etc.)

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GNU/Linux filesystem structure (3)

/tmp/ T e m p o rary fi le s

/usr/ R e g u lar u s e r to o ls (n o t e s s e n tial to th e

s ys te m )

/usr/bin/, /usr/lib/, /usr/sbin.../usr/local/      S p e c i fi c s o ftw are i n s talle d b y th e

s ysad m in

(o fte n p re fe rre d to /opt/)

/var/ D ata u s e d b y th e sys te m o r s ys te m

s e rve rs

/var/log/, /var/spool/mail (i n co m in g

m ai l), /var/spool/lpd (p ri n t jo b s )...

T h e U n i x fi le sys te m s tru c tu re i s d e fi n e d

b y th e F i le sys te m H i e rarch y S tan d ard (F H S ):

h ttp ://w w w .p ath n am e .co m /fh s/

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The Unix and GNU/Linux command line

Shells and File Handling

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Command line interpreters

S h e lls : to o ls to e x e cu te u s e r co m m an d s

C alle d “s h e lls ” b e cau s e th e y h i d e th e d e tai ls o n

th e u n d e rlyin g o p e rati n g sys te m u n d e r th e

s h e ll's s u rface .

C o m m an d s are i n p u t i n a te x t te rm in al, e i th e r a

w in d o w i n a g rap h i cal e n vi ro n m e n t o r a te x t-

o n ly co n so le .

R e s u lts are also d i s p laye d o n th e te rm in al. N o

g rap h i c s are n e e d e d at all.

S h e lls can b e s c ri p te d : p ro vi d e all th e

re s o u rce s to w ri te co m p le x p ro g ram s (variab le ,

c o n d i ti o n als , i te rati o n s ...)

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Well known shells

M o st fam o u s an d p o p u lar s h e lls

bash: The Bourne Again shell (most popular)An improved implementation of sh with lots of added features too.

sh: T h e B o u rn e s h e ll (o b s o le te )

T rad i ti o n al, b as i c s h e ll fo u n d o n U n i x s ys te m s , b y

S te ve B o u rn e .

csh: T h e C s h e ll (o b s o le te )

O n ce p o p u lar s h e ll w i th a C -li k e s yn tax

tcsh: T h e T C s h e ll (s ti ll ve ry p o p u lar)

A C s h e ll co m p ati b le im p le m e n tati o n w i th e vo lve d

fe atu re s (co m m an d co m p le ti o n , h i s to ry e d i ti n g an d

m o re ...)

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fish: a great new shellT h e F ri e n d ly I n te ractive S H e ll

h ttp ://w w w .fi s h s h e ll.o rg /

S tan d ard fe atu re s : h i s to ry, c o m m an d an d fi le

co m p le ti o n ...

B ran d n e w fe atu re s : co m m an d o p ti o n co m p le ti o n ,

co m m an d co m p le ti o n w i th s h o rt d e s cri p ti o n , s yn tax

h i g h li g h ti n g ..

E as i e r to an y o p e n fi le s : open b u i lt-i n c o m m an d .

M u ch s im p le r an d co n s i s te n t syn tax (n o t PO S I X

co m p lian t)

M ak e s i t e as i e r to cre ate s h e ll s cri p ts .

C o m m an d li n e b e g i n n e rs can le arn m u ch fas te r!

E ve n e x p e ri e n c e d u s e rs s h o u ld fi n d th i s s h e ll ve ry

co n ve n i e n t.

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ls command

ls ­a (all)

L i s ts all th e fi le s

(i n c lu d i n g .* fi le s )

ls ­l (lo n g )

L o n g li s ti n g (typ e , d ate ,

s i z e , o w n e r, p e rm i s s i o n s )

ls ­t (time)Lists the most recent files first

ls ­S (s i z e )

L i s ts th e b i g g e s t fi le s fi rs t

ls ­r (re ve rs e )

R e ve rs e s th e s o rt o rd e r

ls ­ltr (o p ti o n s can b e

com b in e d )

L o n g li s ti n g , m o s t re ce n t

fi le s at th e e n d

Lists the files in the current directory, in alphanumeric order,except files starting with the “.” character.

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File name pattern substitutions

B e tte r i n tro d u ce d b y e x am p le s !

ls *txtT h e s h e ll fi rs t re p lace s *txt b y all th e fi le an d

d i re c to ry n am e s e n d i n g b y txt (i n c lu d i n g .txt),

e x c e p t th o s e s tarti n g w i th ., an d th e n e x e cu te s th e

ls co m m an d li n e .

ls ­d .*L i s ts all th e fi le s an d d i re c to ri e s s tarti n g w i th .­d te lls ls n o t to d i s p lay th e co n te n ts o f d i re c to ri e s .

cat ?.logD i s p lays all th e fi le s w h i c h n am e s s tart b y 1

ch aracte r an d e n d b y .log

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Special directories (1)

./

The current directory. Useful for commands taking a directory argument. Also sometimes useful to run commands in the current directory (see later).

So ./readme.txt and readme.txt are equivalent.

../

T h e p are n t (e n clo s i n g ) d i re c to ry. Alw ays b e lo n g s to

th e  . d i re cto ry (s e e ls ­a). O n ly re fe re n ce to th e

p are n t d i re cto ry.

T yp i cal u sag e :

cd ..

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Special directories (2)

~/

N o t a s p e c ial d i re c to ry i n d e e d . S h e lls ju s t

s u b s ti tu te i t b y th e h o m e d i re c to ry o f th e

c u rre n t u s e r.

C an n o t b e u s e d i n m o s t p ro g ram s , as i t i s n o t a

re al d i re c to ry.

~vuhung/

S im i larly, s u b s ti tu te d b y s h e lls b y th e h o m e

d i re c to ry o f th e vuhung u s e r.

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The cd and pwd commands

cd <dir>C h an g e s th e c u rre n t d i re c to ry to <dir>.

cd ­Gets back to the previous current directory.

pwdD i s p lays th e c u rre n t d i re c to ry ("w o rk i n g

d i re c to ry").

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The cp command

cp <source_file> <target_file>C o p i e s th e s o u rce fi le to th e targ e t.

cp file1 file2 file3 ... dirC o p i e s th e fi le s to th e targ e t d i re c to ry (las t

arg u m e n t).

cp ­i (i n te ractive )

Ask s fo r u s e r c o n fi rm ati o n i f th e targ e t fi le

alre ad y e x i s ts

cp ­r <source_dir> <target_dir> (re cu rs ive )

C o p i e s th e w h o le d i re c to ry.

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Smart directory copy with rsync

rsync (re m o te s yn c ) h as b e e n d e s i g n e d to k e e p i n

syn c

d i re cto ri e s o n 2 m ach i n e s w i th a lo w b an d w i d th

co n n e c ti o n .

O n ly co p i e s fi le s th at h ave ch an g e d . F i le s w i th th e sam e

s i ze are co m p are d b y ch e ck su m s .

O n ly tran s fe rs th e b lo ck s th at d i ffe r w i th i n a fi le !

C an co m p re s s th e tran s fe rre d b lo ck s

Pre s e rve s sym b o li c li n k s an d fi le p e rm i s s i o n s : als o ve ry

u s e fu l fo r co p i e s o n th e sam e m ach i n e .

C an w ork th ro u g h s s h (s e cu re re m o te s h e ll). Ve ry u s e fu l

to u p d ate th e co n te n ts o f a w e b s i te , fo r e xam p le .

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rsync examples (1)

rsync ­a /home/vuhung/work /home/backup/work

­a: archive mode. Equivalent to ­rlptgoD... easy way to tell you want recursion and want to preserve almost everything.

rsync ­Pav ­­delete /home/vuhung/work/ /home/backup/work/

­P: ­­partial (keep partially transferred files) and ­­progress (show progress during transfer)

­­delete: delete files in the target which don't exist in the source.

Caution: directory names should end with / .  Otherwise, you get abackup/work/ directory at the destination.

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rsync examples (2)

Copying to a remote machine

rsync ­Pav /home/vuhung/work/001.svn/ \ vuhung@192.168.52.123:/home/work/002.ipad/

User vuhung will be prompted for a password.

Copying from a remote machine through ssh

rsync ­Pav ­e ssh vuhung@192.168.52.123:/home/vuhung/work/ \tmp/work/

User vuhung will be prompted for his ssh key password.

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mv and rm commands

mv <old_name> <new_name>  (move)R e n am e s th e g ive n fi le o r d i re cto ry.

mv ­i (interactive)I f th e n e w fi le alre ad y e x i ts , as k s fo r u s e r co n fi rm

rm file1 file2 file3 ... (remove)R e m o ve s th e g ive n fi le s .

rm ­i (i n te ractive )

Alw ays as k fo r u s e r co n fi rm .

rm ­r dir1 dir2 dir3 (re cu rs ive )

R e m o ve s th e g ive n d i re c to ri e s w i th all th e i r

co n te n ts .

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Create and delete directories

mkdir dir1 dir2 dir3 ... (make dir)C re ate s d i re c to ri e s w i th th e g ive n n am e s .

rmdir dir1 dir2 dir3 ... (remove dir)R e m o ve s th e g ive n d i re c to ri e s

S afe : o n ly w o rk s w h e n d i re c to ri e s an d e m p ty.

Alte rn ative : rm ­r (doesn't need empty directories).

mkdir ­p /dir1/dir2/dir3

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Displaying file contents

S e ve ral w ays o f d i s p layi n g th e co n te n ts o f fi le s .

cat file1 file2 file3 ... (concatenate)C o n cate n ate s an d o u tp u ts th e co n te n ts o f th e g ive n

fi le s .

more file1 file2 file3 ...Afte r e ach p ag e , as k s th e u s e r to h i t a k e y to

co n ti n u e .

C an also ju m p to th e fi rs t o ccu rre n ce o f a k e yw o rd

(/ c o m m an d ).

less file1 file2 file3 ...D o e s m o re th an more w i th le s s .

D o e sn 't re ad th e w h o le fi le b e fo re s tarti n g .

S u p p o rts b ack w ard m o ve m e n t i n th e fi le (?

co m m an d ).

“m o re i s le s s ”

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The head and tail commands

head [­<n>] <file>D i s p lays th e fi rs t < n > li n e s (o r 1 0 b y d e fau lt) o f th e g ive n fi le .

D o e s n 't h ave to o p e n th e w h o le fi le to d o th i s !

tail [­<n>] <file>D i s p lays th e las t < n > li n e s (o r 1 0 b y d e fau lt) o f th e g ive n fi le .

N o n e e d to lo ad th e w h o le fi le i n R AM ! Ve ry u s e fu l fo r h u g e

fi le s .

tail ­f <file> (follow)D i s p lays th e las t 1 0 li n e s o f th e g ive n fi le an d c o n ti n u e s to

d i s p lay n e w li n e s w h e n th e y are ap p e n d e d to th e fi le .

Ve ry u s e fu l to fo llo w th e c h an g e s i n a lo g fi le , fo r e x am p le .

E x am p le s

head /etc/passwdtail ­f /var/log/httpd/acces_log

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The grep command

grep <pattern> <files>S can s th e g i ve n fi le s an d d i s p lays th e li n e s w h i ch m atch

th e g i ve n p atte rn .

grep URGETN *.logD i s p lays all th e li n e s co n tai n i n g error i n th e *.log fi le s

grep ­i URGENT *.logS am e , b u t cas e i n s e n s i ti ve

grep ­ri URGENT .S am e , b u t re cu rs i ve ly i n all th e fi le s i n . an d i ts

s u b d i re cto ri e s

grep ­v INFO *.logO u tp u ts all th e li n e s i n th e fi le s e x ce p t th o s e co n tai n i n g

info.

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The sort command

sort <file>S o rts th e li n e s i n th e g ive n fi le i n c h aracte r

o rd e r an d o u tp u ts th e m .

sort ­r <file>S am e , b u t i n re ve rs e o rd e r.

sort ­ru <file>u: u n i q u e . S am e , b u t ju s t o u tp u ts i d e n ti cal

li n e s o n c e .

M o re p o s s i b i li ti e s d e s cri b e d late r!

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Symbolic links

A sym b o li c li n k i s a s p e c ial fi le w h i c h

i s ju s t a re fe re n ce to th e n am e o f

an o th e r o n e (fi le o r d i re c to ry):

U s e fu l to re d u c e d i s k u sag e an d

co m p le x i ty w h e n 2 fi le s h ave th e sam e

co n te n t.

E x am p le :

/var/lo g /s e cu re   /home/var.log.secure→

H o w to i d e n ti fy sym b o li c li n k s :

ls ­l d i s p lays ­> an d th e li n k e d fi le n am e .

G N U ls d i s p lays li n k s w i th a d i ffe re n t co lo r.

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Creating symbolic links

T o cre ate a sym b o li c li n k (sam e o rd e r as i n cp):

ln ­s file_name link_name

T o cre ate a li n k w i th to a fi le i n an o th e r

d i re c to ry, w i th th e sam e n am e :

ln ­s ../README.txt

T o cre ate m u lti p le li n k s at o n ce i n a g ive n

d i re c to ry:

ln ­s file1 file2 file3 ... dir

T o re m o ve a li n k :

rm link_nameOf course, this doesn't remove the linked file!

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Hard links

T h e d e fau lt b e h avio r fo r ln i s to c re ate hard links

A hard link to a fi le i s a re g u lar fi le w i th e xactly

th e sam e p h ys i cal co n te n ts

W h i le th e y s ti ll save s p ace , h ard li n k s can 't b e

d i s ti n g u i s h e d fro m th e o rig i n al fi le s .

I f yo u re m o ve th e o rig i n al fi le , th e re i s n o

im p act o n th e h ard li n k c o n te n ts .

T h e c o n te n ts are re m o ve d w h e n th e re are n o

m o re fi le s (h ard li n k s ) to th e m .

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Files names and inodes

M ak e s h ard an d s ym b o li c (s o ft) li n k s

e as i e r to u n d e rs tan d !

Inode

File Hard linkSoft link

Inodeinterface

File name interface

Filesystem

Users

rmrm

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File access rights

3 typ e s o f acce s s ri g h ts

R e ad acce s s (r)

W ri te acce s s (w)

E x e cu te ri g h ts (x)

3 typ e s o f acce s s le ve ls

U s e r (u): fo r th e o w n e r

o f th e fi le

G ro u p (g): e ach fi le also

h as a “g ro u p ” attri b u te ,

co rre s p o n d i n g to a g ive n

li s t o f u s e rs

O th e rs (o): fo r all o th e r

u s e rs

Use ls ­l to check file access rights

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Access right constraints

x w i th o u t r i s le g al b u t i s u s e le s s

Yo u h ave to b e ab le to re ad a fi le to e x e cu te i t.

B o th r an d x p e rm i s s i o n s n e e d e d fo r d i re cto ri e s :

x to e n te r, r to li s t i ts co n te n ts .

Yo u can 't re n am e , re m o ve , c o p y fi le s i n a d i re cto ry

i f yo u d o n 't h ave w acce s s to th i s d i re cto ry.

I f yo u h ave w acc e s s to a d i re cto ry, yo u C AN

re m o ve a fi le e ve n i f yo u d o n 't h ave w ri te acce s s to

th i s fi le (re m e m b e r th at a d i re c to ry i s ju s t a fi le

d e s cri b i n g a li s t o f fi le s ). T h i s e ve n le ts yo u m o d i fy

(re m o ve + re cre ate ) a fi le e ve n w i th o u t w acce s s to

i t.

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Access rights examples

­rw­r­­r­­R e ad ab le an d w ri tab le fo r fi le o w n e r, o n ly re ad ab le

fo r o th e rs

­rw­r­­­­­R e ad ab le an d w ri tab le fo r fi le o w n e r, o n ly re ad ab le

fo r u s e rs b e lo n g i n g to th e fi le g ro u p .

drwx­­­­­­D i re cto ry o n ly acce s s i b le b y i ts o w n e r

­­­­­­­r­xF i le e x e cu tab le b y o th e rs b u t n e i th e r b y yo u r

fri e n d s n o r b y yo u rs e lf. N i c e p ro te cti o n s fo r a

trap ...

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chmod: changing permissions

chmod <permissions> <files>2 fo rm ats fo r p e rm i s s i o n s :

O ctal fo rm at (ab c ):

a,b,c = r*4+w*2+x (r, w, x: b o o le an s )

E xam p le : chmod 644 <file>(rw fo r u, r fo r g an d o)

O r sym b o li c fo rm at. E asy to u n d e rs tan d b y

e xam p le s :

chmod go+r: ad d re ad p e rm i s s i o n s to g ro u p an d

o th e rs .

chmod u­w: re m o ve w ri te p e rm i s s i o n s fro m

u s e r.

chmod a­x: (a: all) re m o ve e x e cu te p e rm i s s i o n

fro m all.

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More chmod (1)

chmod ­R a+rX folder/M ak e s folder an d e ve ryth i n g i n i t

avai lab le to e ve ryo n e !

R: ap p ly c h an g e s re cu rs ive ly

X: x, b u t o n ly fo r d i re c to ri e s an d fi le s

alre ad y e x e cu tab le

Ve ry u s e fu l to o p e n re cu rs ive acce s s to

d i re c to ri e s , w i th o u t ad d i n g e x e cu ti o n ri g h ts

to all fi le s .

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More chmod (2)

chmod a+t /tmp

t: (sticky). Special permission for directories, allowing only the directory and file owner to delete a file in a directory.

Useful for directories with write access to anyone,like /tmp.

Displayed by ls ­l with a t character.

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The Unix and GNU / Linux command line

Standard I/O, Redirections, Pipes

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Standard output

M o re ab o u t co m m an d o u tp u t

All th e co m m an d s o u tp u tti n g te x t o n

yo u r te rm in al d o i t b y w ri ti n g to th e i r

stand ard outp ut.

S tan d ard o u tp u t can b e w ri tte n

(re d i re c te d ) to a fi le u s i n g th e >

s ym b o l

S tan d ard o u tp u t can b e ap p e n d e d to

an e x i s ti n g fi le u s i n g th e >> s ym b o l

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Standard output redirection examples

ls ~vuhung/* > ~vuhung/vuhung­home­list.txt

cat america.txt > the_earth.txtcat america.txt >> the_world.txt

echo “README: No such file or directory” > READMEUseful way of creating a file without a text editor.Nice Unix joke too in this case.

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Standard input

M o re ab o u t co m m an d i n p u t

L o ts o f co m m an d s , w h e n n o t g ive n i n p u t

arg u m e n ts , can tak e th e i r i n p u t fro m stand ard inp ut.

sortwindowslinux[Ctrl][D]linuxwindows

sort < participants.txtT h e s tan d ard i n p u t o f s o rt i s tak e n fro m th e g ive n

fi le .

sort takes its input fromthe standard input: in this case,what you type in the terminal(ended by [Ctrl][D])

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Pipes

U n ix p i p e s are ve ry u s e fu l to re d i re ct th e s tan d ard

o u tp u t o f a co m m an d to th e s tan d ard i n p u t o f

an o th e r o n e .

E x am p le s

cat *.log | grep ­i error | sort

grep ­ri error . | grep ­v “ignored” | sort ­u \ > serious_errors.log

cat /home/*/homework.txt | grep grade | more

T h i s o n e o f th e m o s t p o w e rfu l fe atu re s i n U n i x

s h e lls !

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The tee command

tee [­a] file

T h e tee c o m m an d can b e u s e d to s e n d

s tan d ard o u tp u t to th e s cre e n an d to a fi le

s im u ltan e o u s ly.

make | tee build.logR u n s th e make c o m m an d an d s to re s i ts

o u tp u t to build.log.

make install | tee ­a build.logR u n s th e make install c o m m an d an d

ap p e n d s i ts o u tp u t to build.log.

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Standard error

E rro r m e s sag e s are u s u ally o u tp u t (i f th e p ro g ram

i s w e ll w ri tte n ) to stand ard e rror i n s te ad o f

s tan d ard o u tp u t.

S tan d ard e rro r can b e re d i re cte d th ro u g h 2> o r 2>>

E x am p le :

cat f1 f2 nofile > newfile 2> error_file

Note: 1 is the descriptor for standard output, so 1> is equivalent to >.

C an re d i re ct b o th s tan d ard o u tp u t an d s tan d ard

e rro r to th e sam e fi le u s i n g &> :cat f1 f2 nofile &> whole_file

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The yes commandU se fu l to fi ll s tan d ard i n p u t w i th

alw ays th e sam e s tri n g .

yes <string> | <command>K e e p s fi lli n g th e s tan d ard i n p u t o f

<command> w i th <string> (y b y

d e fau lt).

E x am p le s

yes | rm ­r dir/bank> yes no | credit_applicantyes "" | make oldconfig (equivalent to hitting [Enter] to accept all default settings)

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Special devices (1)

D e vi c e fi le s w i th a s p e c ial b e h avio r o r co n te n ts

/dev/nullT h e d ata s i n k ! D i s card s all d ata w ri tte n to th i s fi le .

U s e fu l to g e t ri d o f u n w an te d o u tp u t, typ i cally lo g

i n fo rm ati o n :

mplayer big_buck_bunny_1080p_surround.avi &> /dev/null

/dev/zeroR e ad s fro m th i s fi le alw ays re tu rn \0 c h aracte rs

U s e fu l to c re ate a fi le fi lle d w i th ze ro s :

dd if=/dev/zero of=disk.img bs=1k count=2048

S e e man null o r man zero fo r d e tai ls

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Special devices (2)/dev/randomR e tu rn s ran d o m b yte s w h e n re ad . M ain ly u s e d b y

cryp to g rap h i c p ro g ram s . U s e s i n te rru p ts fro m

s o m e d e vi c e d rive rs as s o u rce s o f tru e ran d o m n e s s

(“e n tro p y”).

R e ad s can b e b lo ck e d u n ti l e n o u g h e n tro p y i s

g ath e re d .

/dev/urandomF o r p ro g ram s fo r w h i c h p s e u d o ran d o m n u m b e rs

are fi n e .

Alw ays g e n e rate s ran d o m b yte s , e ve n i f n o t e n o u g h

e n tro p y i s avai lab le (i n w h i c h cas e i t i s p o s s i b le ,

th o u g h s ti ll d i ffi c u lt, to p re d i c t fu tu re b yte

s e q u e n ce s fro m p as t o n e s ).

S e e man random fo r d e tai ls .

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Special devices (3)

/dev/fullM im i c s a fu ll d e vi c e .

U s e fu l to c h e ck th at yo u r ap p li cati o n p ro p e rly

h an d le s

th i s k i n d o f s i tu ati o n .

S e e man full fo r d e tai ls .

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The Unix and GNU / Linux command line

Task Control

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Full control on tasks

S in c e th e b e g i n n i n g , U n i x s u p p o rts

tru e p re e m p tive m u lti task i n g .

Ab i li ty to ru n m an y task s i n p aralle l,

an d ab o rt th e m e ve n i f th e y co rru p t

th e i r o w n s tate an d d ata.

Ab i li ty to c h o o s e w h i c h p ro g ram s yo u

ru n .

Ab i li ty to c h o o s e w h i c h i n p u t yo u r

p ro g ram s tak e s , an d w h e re th e i r

o u tp u t g o e s .

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Processes

“E ve ryth i n g i n U n i x i s a fi le

E ve ryth i n g i n U n i x th at i s n o t a fi le i s a p ro ce s s ”

Pro ce s s e s

I n s tan ce s o f a ru n n i n g p ro g ram s

S e ve ral i n s tan ce s o f th e sam e p ro g ram can ru n at

th e sam e tim e

D ata as so c iate d to p ro ce s s e s :

O p e n fi le s , allo cate d m e m o ry, s tack , p ro ce s s i d ,

p are n t, p ri o ri ty, s tate ...

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Running jobs in background

S am e u sag e th ro u g h o u t all th e s h e lls

U s e fu l

F or co m m an d li n e jo b s w h i ch o u tp u t can b e

e xam in e d late r, e s p e c ially fo r tim e

co n s u m in g o n e s .

T o s tart g rap h i cal ap p li cati o n s fro m th e

co m m an d li n e an d th e n co n ti n u e w i th th e

m o u s e .

S tarti n g a tas k : ad d & at th e e n d o f

yo u r li n e :

find_prince_charming ­­cute ­­clever ­­rich &

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Background job control

jobsR e tu rn s th e li s t o f b ack g ro u n d jo b s fro m th e sam e

s h e ll

[1]­  Running ~/bin/find_meaning_of_life ­­without­god &[2]+  Running make mistakes &

fgfg %<n>Pu ts th e las t / n th b ack g ro u n d jo b i n fo re g ro u n d

m o d e

M o vin g th e cu rre n t task i n b ack g ro u n d m o d e :

[Ctrl] Zbg

kill %<n>Aborts the nth job.

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Job control example

> jobs[1]­  Running ~/bin/find_meaning_of_life ­­without­god &[2]+  Running make mistakes &

> fgmake mistakes

> [Ctrl] Z[2]+  Stopped make mistakes

> bg[2]+ make mistakes &

> kill %1[1]+  Terminated ~/bin/find_meaning_of_life ­­without­god

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Listing all processes

... whatever shell, script or process they are started from

ps ­uxLists all the processes belonging to the current user

ps ­aux (N o te : ps ­edf o n S ys te m V sys te m s )

L i s ts all th e p ro ce s s e s ru n n in g o n th e s ys te m

ps ­aux | grep bart | grep bashUSER       PID %CPU %MEM   VSZ  RSS TTY      STAT START   TIME COMMANDbart      3039  0.0  0.2  5916 1380 pts/2    S    14:35   0:00 /bin/bashbart      3134  0.0  0.2  5388 1380 pts/3    S    14:36   0:00 /bin/bashbart      3190  0.0  0.2  6368 1360 pts/4    S    14:37   0:00 /bin/bashbart      3416  0.0  0.0     0    0 pts/2    RW   15:07   0:00 [bash]

PID:  Process idVSZ:  Virtual process size (code + data + stack)RSS:  Process resident size: number of KB currently in RAMTTY:  TerminalSTAT:  Status: R (Runnable), S (Sleep), W (paging), Z (Zombie)...

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Live process activitytop ­ D i s p lays m o s t im p o rtan t p ro ce s s e s , s o rte d

b y cp u p e rce n tag e

top ­ 15:44:33 up  1:11,  5 users,  load average: 0.98, 0.61, 0.59Tasks:  81 total,   5 running,  76 sleeping,   0 stopped,   0 zombieCpu(s): 92.7% us,  5.3% sy,  0.0% ni,  0.0% id,  1.7% wa,  0.3% hi,  0.0% siMem:    515344k total,   512384k used,     2960k free,    20464k buffersSwap:  1044184k total,        0k used,  1044184k free,   277660k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND3809 vuhung      25   0  6256 3932 1312 R 93.8  0.8   0:21.49 bunzip22769 root      16   0  157m  80m  90m R  2.7 16.0   5:21.01 X

h to p : I m p ro ve d to p

Yo u can ch an g e th e s o rti n g o rd e r b y typ i n g

M: M e m o ry u sag e , P: % C PU , T: T im e .

Yo u can k i ll a task b y typ i n g k an d th e p ro ce s s i d .

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Live process activityhtop ­ D i s p lays m o s t im p o rtan t p ro ce s s e s , s o rte d

b y cp u p e rce n tag e

top ­ 15:44:33 up  1:11,  5 users,  load average: 0.98, 0.61, 0.59Tasks:  81 total,   5 running,  76 sleeping,   0 stopped,   0 zombieCpu(s): 92.7% us,  5.3% sy,  0.0% ni,  0.0% id,  1.7% wa,  0.3% hi,  0.0% siMem:    515344k total,   512384k used,     2960k free,    20464k buffersSwap:  1044184k total,        0k used,  1044184k free,   277660k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND3809 jdoe      25   0  6256 3932 1312 R 93.8  0.8   0:21.49 bunzip22769 root      16   0  157m  80m  90m R  2.7 16.0   5:21.01 X3006 jdoe      15   0 30928  15m  27m S  0.3  3.0   0:22.40 kdeinit3008 jdoe      16   0  5624  892 4468 S  0.3  0.2   0:06.59 autorun3034 jdoe      15   0 26764  12m  24m S  0.3  2.5   0:12.68 kscd3810 jdoe      16   0  2892  916 1620 R  0.3  0.2   0:00.06 top

Yo u can ch an g e th e s o rti n g o rd e r b y typ i n g

M: M e m o ry u sag e , P: % C PU , T: T im e .

Yo u can k i ll a task b y typ i n g k an d th e p ro ce s s i d .

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Killing processes (1)kill <pids>S e n d s an ab o rt s i g n al to th e g ive n p ro ce s s e s .

L e ts p ro ce s s e s save d ata an d e x i t b y

th e m s e lve s . S h o u ld b e u s e d fi rs t. E x am p le :

kill 3039 3134 3190 3416

kill ­9 <pids>S e n d s an im m e d iate te rm in ati o n s i g n al. T h e

sys te m i ts e lf te rm in ate s th e p ro ce s s e s . U s e fu l

w h e n a p ro c e s s i s re ally s tu ck (d o e sn 't an sw e r

to kill ­1).

kill ­9 ­1K i lls all th e p ro ce s s e s o f th e c u rre n t u s e r. ­1:

m e an s all p ro ce s s e s .

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Killing processes (2)

killall [­<signal>] <command>K i lls all th e jo b s ru n n i n g <command>. E xam p le :

killall bash

xkillLets you kill a graphical application by clicking on it!Very quick! Convenient when you don't know the application command name.

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Recovering from stuck graphics

I f yo u r g rap h i cal s e s s i o n i s s tu ck an d yo u can n o lo n g e r

typ e i n yo u r te rm i n als , d o n 't re b o o t!

I t i s ve ry li k e ly th at yo u r sys te m i s s ti ll fi n e . T ry to

acce s s a te x t co n so le b y p re s s i n g th e [Ctrl][Alt][F1]

k e ys

(o r [F2],[F3] fo r m o re te x t co n so le s )

I n th e te x t co n so le , yo u can try to k i ll th e g u i lty

ap p li cati o n .

O n ce th i s i s d o n e , yo u can g o b ack to th e g rap h i c

s e s s i o n b y p re s s i n g [Ctrl][Alt][F5] or [Ctrl][Alt][F7] (depending on your distribution)

If you can't identify the stuck program, you can also kill all your processes: kill ­9 ­1You are then brought back to the login screen.

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Sequential commands

C an typ e th e n e x t co m m an d i n yo u r te rm in al e ve n

w h e n th e c u rre n t o n e i s n o t o ve r.

C an s e p arate co m m an d s w i th th e ; s ym b o l:

echo “I love thee”; sleep 10;  echo “ not”

C o n d i ti o n als : u s e || (o r) o r && (an d ):

more God || echo “Sorry, God doesn't exist”Runs echo only if the first command fails

ls ~sd6 && cat ~sd6/* > ~sydney/recipes.txtOnly cats the directory contents if the ls command succeeds (means read access).

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Quoting (1)

D o u b le (") q u o te s can b e u s e d to p re ve n t th e s h e ll

fro m i n te rp re ti n g s p ace s as arg u m e n t s e p arato rs ,

as w e ll as to p re ve n t fi le n am e p atte rn e x p an s i o n .

> echo "Hello World"Hello World

> echo "You are logged as $USER"You are logged as vuhung

> echo *.logfind_prince_charming.log cosmetic_buys.log

> echo "*.log"*.log

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Quoting (2)

S i n g le q u o te s b ri n g a s im i lar fu n c ti o n ali ty, b u t

w h at i s b e tw e e n q u o te s i s n e ve r s u b s ti tu te d

> echo 'You are logged as $USER'You are logged as $USER

Back quotes (`) can be used to call a command within another

> cd /lib/modules/`uname ­r`; pwd/lib/modules/2.6.9­1.6_FC2

Back quotes can be used within double quotes

> echo "You are using Linux `uname ­r`"You are using Linux 2.6.9­1.6_FC2

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Measuring elapsed time

time find_expensive_housing ­­near<...command output...>real    0m2.304s (actual elapsed time)user    0m0.449s (CPU time running program code)sys     0m0.106s (CPU time running system calls)

real = user + sys + waitingwaiting = I/O waiting time + idle time (running other tasks)

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Environment variables

S h e lls le t th e u s e r d e fi n e variab le s.

T h e y can b e re u s e d i n s h e ll co m m an d s .

C o n ve n ti o n : lo w e r cas e n am e s

e x p o rt M YN AM E = 'vu h u n g '

Yo u can also d e fi n e e nvironm ent variab le s:

variab le s th at are als o vi s i b le w i th i n s cri p ts

o r e x e cu tab le s calle d fro m th e s h e ll.

C onve ntion : up p e r case nam e s.

$setL i s ts all d e fi n e d e n vi ro n m e n t variab le s an d

th e i r valu e .

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Shell variables examples

S h e ll variab le s (b ash )

projdir=/home/vuhung/coolstuffls ­la $projdir; cd $projdir

E n vi ro n m e n t variab le s (b ash )

cd $HOME

export DEBUG=1./find_extraterrestrial_life(displays debug information if DEBUG is set)

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Main standard environment variables

LD_LIBRARY_PATHS h are d li b rary s e arch p ath

DISPLAYS cre e n i d to d i s p lay X

(g rap h i cal) ap p li cati o n s o n .

EDITORD e fau lt e d i to r (vi , e m acs ...)

HOMEC u rre n t u s e r h o m e

d i re c to ry

HOSTNAMEN am e o f th e lo cal m ach i n e

MANPATHM an u al p ag e s e arch p ath

PATHC o m m an d s e arch p ath

PRINTERD e fau lt p ri n te r n am e

SHELLC u rre n t s h e ll n am e

TERMC u rre n t te rm i n al typ e

USERC u rre n t u s e r n am e

Extremely widely used!

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PATH environment variables

PATHS p e c i fi e s th e s h e ll s e arch o rd e r fo r co m m an d s

/home/vuhung/bin:/usr/local/bin:/usr/kerberos/bin:

/usr/bin:/bin:/usr/X11R6/bin:/bin:/usr/bin

LD_LIBRARY_PATHS p e c i fi e s th e s h are d li b rary (b i n ary co d e li b rari e s

s h are d b y ap p li cati o n s , li k e th e C li b rary) s e arch o rd e r

fo r ld

/usr/local/lib:/usr/lib:/lib:/usr/X11R6/lib

MANPATHS p e c i fi e s th e s e arch o rd e r fo r m an u al p ag e s

/usr/local/man:/usr/share/man

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PATH usage warning

I t i s s tro n g ly re co m m e n d e d n o t to h ave th e “.”

d i re c tory i n yo u r PATH e n vi ro n m e n t variab le , i n

p arti cu lar n o t at th e b e g i n n i n g :

A crack e r co u ld p lace a m ali c i o u s ls fi le i n yo u r

d i re c tori e s . I t w ou ld g e t e x e cu te d w h e n yo u ru n ls i n

th i s d i re cto ry an d co u ld d o n au g h ty th i n g s to you r d ata.

I f yo u h ave an e x e cu tab le fi le calle d test i n a d i re cto ry,

th i s w i ll o ve rri d e th e d e fau lt test p ro g ram an d s o m e

s cri p ts w i ll s to p w ork i n g p ro p e rly.

E ach tim e yo u cd to a n e w d i re c to ry, th e s h e ll w i ll w as te

tim e u p d ati n g i ts li s t o f avai lab le com m an d s .

C all yo u r lo cal co m m an d s as fo llo w s : ./test

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Alias

S h e lls le t yo u d e fi n e com m an d aliase s: s h o rtcu ts fo r

com m an d s yo u u s e ve ry fre q u e n tly.

E xam p le s

alias ls='ls ­la'Useful to always run commands with default arguments.

alias rm='rm ­i'U s e fu l to m ak e rm alw ays as k fo r co n fi rm atio n .

alias frd='find_rambaldi_device ­­asap ­­risky'Useful to replace very long and frequent commands.

alias cia='. /home/vuhung/env/cia.sh'Useful to set an environment in a quick way(. is a shell command to execute the content of a shell script).

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The which command

B e fo re yo u ru n a co m m an d , which te lls yo u w h e re

i t i s fo u n d

bash> which lsalias ls='ls ­­color=tty'        /bin/ls

tcsh> which lsls:      aliased to ls ­­color=tty

bash> which alias/usr/bin/which: no alias in (/usr/local/bin:/usr/bin:/bin:/usr/X11R6/bin)

tcsh> which aliasalias: shell built­in command.

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~/.bashrc file

~/.bashrc, ~/.bash_profile, /etc/bashrcS h e ll s cri p t re ad e ach tim e a bash

s h e ll i s s tarte d

Yo u can u s e th i s fi le to d e fi n e

Yo u r d e fau lt e n vi ro n m e n t variab le s (PATH,

EDITOR...).

Yo u r alias e s .

Yo u r p ro m p t (s e e th e bash m an u al fo r d e tai ls ).

A g re e ti n g m e s sag e .

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Command editing

Yo u can u s e th e le ft an d ri g h t arro w

k e ys to m o ve th e c u rs o r i n th e c u rre n t

co m m an d .

Yo u can u s e [Ctrl][a] to g o to th e

b e g i n n i n g o f th e li n e , an d [Ctrl][e]

to g o to th e e n d .

Yo u can u s e th e u p an d d o w n arro w s

to s e le c t e arli e r co m m an d s .

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Command history (1)historyD i s p lays th e late s t co m m an d s th at yo u ran an d

th e i r n u m b e r. Yo u can co p y an d p as te co m m an d

s tri n g s .

Yo u can re call th e late s t co m m an d :

!!

Yo u can re call a co m m an d b y i ts n u m b e r

!1003

Yo u can re call th e late s t co m m an d m atch i n g a

s tarti n g s trin g :

!cat

Ctrl­R

Search bash history backward

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Command history (2)

Yo u can m ak e s u b s ti tu ti o n s o n th e

late s t co m m an d :

^more^less

Yo u can ru n an o th e r co m m an d w i th

th e sam e arg u m e n ts :

more !*

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The Unix and GNU / Linux command line

MiscellaneousText Editors

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Text editors

G rap h i cal te x t e d i to rs

F i n e fo r m o s t n e e d s

n e d i t

E m acs , X e m acs

T e x t-o n ly te x t e d i to rs

O fte n n e e d e d fo r sysad m in s an d g re at fo r

p o w e r u s e rs

vi (vim )

n an o

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The gedit text editor

G n o m e g e d i t

B e s t te x t e d i to r fo r n on vi or emacs experts

F e atu re h i g h lig h ts :

Ve ry e asy te x t s e le c ti o n an d m o vi n g

S yn tax h i g h li g h ti n g fo r m o s t lan g u ag e s an d

fo rm ats . C an b e tai lo re d fo r yo u r o w n lo g

fi le s , to h i g h li g h t p arti c u lar e rro rs an d

w arn i n g s .

E asy to cu s to m i z e th ro u g h m e n u s

I n s talle d b y d e fau lt b y m o s t

d i s tri b u ti o n s

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gedit screenshot

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Emacs/Xemacs

E m acs an d X e m acs are p re tty

s im i lar (u p to yo u r

p re fe re n c e )

E x tre m e ly p o w e rfu l te x t

e d i to r fe atu re s

G re at fo r p o w e r u s e rs

L e s s e rg o n o mic than nedit

N o n s tan d ard s h o rtcu ts

M u ch m o re th an a te x t e d i to r

(g am e s , e -m ai l, s h e ll,

b ro w s e r).

S o m e p o w e r co m m an d s h ave

to b e le arn t.

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vi (vim)

T e x t-m o d e te x t e d i to r avai lab le i n all

U n i x s ys te m s . C re ate d b e fo re

co m p u te rs w i th m i c e ap p e are d .

D i ffi c u lt to le arn fo r b e g i n n e rs u s e d to

g rap h i cal te x t e d i to rs .

Ve ry p ro d u c tive fo r p o w e r u s e rs .

O fte n can 't b e re p lace d to e d i t fi le s i n

s ys te m ad m in i s trati o n o r i n E m b e d d e d

S ys te m s , w h e n yo u ju s t h ave a te x t

co n so le .

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vim - vi improved

vi im p le m e n tati o n n o w fo u n d i n m o s t G N U /

L i n u x h o s t sys te m s

I m p le m e n ts lo ts o f fe atu re s avai lab le i n

m o d e rn e d i to rs : s yn tax h ig h li g h ti n g ,

co m m an d h i s to ry, h e lp , u n lim i te d u n d o an d

m u ch m u ch m o re .

C o o l fe atu re e xam p le : can d i re ctly o p e n

co m p re s s e d te x t fi le s .

C o m e s w i th a G T K g rap h i cal i n te rface (gvim)

U n fo rtu n ate ly, n o t fre e s o ftw are (b e cau s e o f

a sm all re s tri c ti o n i n fre e d o m to m ak e

ch an g e s )

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vi basic commands

Though vi is extremely powerful, its main 30 commands are easy to learn and are sufficient for 99% of everyone's needs!

You can also take the quick tutorial by running vimtutor.

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GNU nano

An o th e r sm all te x t-o n ly, m o u s e fre e te x t

e d i to r.

An e n h an ce d P i co c lo n e (n on fre e e d i to r i n

P i n e )

F ri e n d ly an d e as i e r to le arn fo r b e g i n n e rs

th an k s to o n s cre e n co m m an d s u m m ari e s .

Avai lab le i n b i n ary p ack ag e s fo r s e ve ral

p latfo rm s .

An alte rn ative to vi i n e m b e d d e d sys te m s .

H o w e ve r, n o t avai lab le as a b u syb o x b u i lt-

i n .

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GNU nano screenshot

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The Unix and GNU/Linux command line

MiscellaneousCompressing and Archiving

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Measuring disc usage

C au ti o n : d i ffe re n t fro m fi le s i z e !

du ­h <file> (d i s k u sag e )

­h: re tu rn s s i z e o n d i s k o f th e g ive n fi le , i n

h u m an re ad ab le fo rm at: K (k i lo b yte s ), M

(m e g ab yte s ) o r G (g ig ab yte s ), . W ith o u t ­h, du

re tu rn s th e raw n u m b e r o f d i s k b lo ck s u s e d b y

th e fi le (h ard to re ad ).

N o te th at th e ­h o p ti o n o n ly e x i s ts i n G N U du.

du ­sh <dir>­s: re tu rn s th e s u m o f d i s k u sag e o f all th e fi le s

i n th e g ive n d i re c to ry.

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Measuring disk space

df ­h <dir>R e tu rn s d i s k u sag e an d fre e s p ace fo r th e

fi le sys te m co n tain i n g th e g ive n d i re c to ry.

S im i larly, th e ­h o p ti o n o n ly e x i s ts i n G N U df.

Example:> df ­h .Filesystem            Size  Used Avail Use% Mounted on/dev/hda5             9.2G  7.1G  1.8G  81% /

df ­hR e tu rn s d i s k s p ace i n fo rm ati o n fo r all

fi le sys te m s avai lab le i n th e sys te m . W h e n

e rro rs h ap p e n , u s e fu l to lo o k fo r fu ll

fi le sys te m s .

d u -s h /

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Compressing

Ve ry u s e fu l fo r s h ri n k i n g h u g e fi le s an d savin g

s p ace

g[un]zip <file>G N U z i p co m p re s s i o n u ti li ty. C re ate s .gz fi le s .

O rd i n ary p e rfo rm an ce (s im i lar to Z i p ).

b[un]zip2 <file>M o re re ce n t an d e ffe ctive co m p re s s i o n u ti li ty.

C re ate s .bz2 fi le s . U s u ally 2 0-2 5 % b e tte r th an gzip.

U s i n g 7-z i p

M u ch b e tte r co m p re s s i o n rati o th an b z i p 2 (u p to 1 0

to 2 0% ).

S e e th e 7-z i p p ag e fo r d e tai ls .

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Archiving (1)

U se fu l to b ack u p o r re le as e a s e t o f fi le s w i th i n

1 fi le

tar: o ri g i n ally “tap e arch ive ”

C re ati n g an arch ive :

tar cvf <archive> <files or directories>c: c re ate

v: ve rb o s e . U s e fu l to fo llo w arch ivi n g p ro g re s s .

f: fi le . Arch ive cre ate d i n fi le (tap e u s e d

o th e rw i s e ).

E xam p le :

tar cvf /backup/home.tar /homebzip2 /backup/home.tar

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Archiving (2)

Vie w in g th e co n te n ts o f an arch ive o r

i n te g ri ty ch e ck :

tar tvf <archive>t: te s t

E x tracti n g all th e fi le s fro m an arch ive :

tar xvf <archive>

E xtracti n g ju s t a fe w fi le s fro m an arch ive :

tar xvf <archive> <files or directories>F i le s o r d i re c to ri e s are g ive n w i th p ath s

re lative to th e arch ive ro o t d i re c to ry.

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Extra options in GNU tar

tar = gtar = G N U tar o n G N U / L i n u x

C an co m p re s s an d u n co m p re s s arch ive s o n th e

fly. U s e fu l to avo i d c re ati n g h u g e i n te rm e d iate

fi le s

M u ch s im p le r to d o th an w i th tar an d bzip2!

j o p ti o n : [u n ]co m p re s s e s o n th e fly w i th bzip2

z o p ti o n : [u n ]co m p re s s e s o n th e fly w i th gzip

E xam p le s

tar cvjf work.tar.bz2 work/

tar cvzf work.tar.gz work/

tar xvzf work.tar.bz2; tar xvjf work.tar.gz

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7-zip (1)h ttp ://w w w .7-z i p .o rg /

N o w th e b e s t s o lu ti o n fo r yo u r arch ive s !

L i c e n s e : G N U L G PL

7-z i p c o m p re s s e s m u ch b e tte r th an b z i p 2 (u p to 1 0 o r

2 0% )

an d o f co u rs e z i p (30 to 5 0 % ).

B e n ch m ark co m p re s s i n g K n o p p i x 5 .0.1 : -2 2 % (vs .

b z i p 2 )!

C au ti o n : 7-z i p can n o t re p lace tar fo r arch ivi n g o n U n i x .

I t d o e sn 't k e e p fi le o w n e r an d g ro u p i n fo rm ati o n ,

b u t o f co u rs e k e e p s fi le p e rm i s s i o n s .

U s e i t to co m p re s s tar arch ive s !

I n vo k e : 7z , 7za

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7-zip (2)

7-z i p s u p p o rts s tro n g AE S -2 5 6 e n cryp ti o n .

N o n e e d to e n cryp t i n a s e p arate p as s .

At las t a s o lu ti o n avai lab le fo r U n i x an d W in d o w s !

T h e to o l s u p p o rts m o s t o th e r co m p re s s i o n fo rm ats :

zip, cab , arj, g z i p , b z i p 2 , tar, cp i o , rp m an d d e b .

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Using 7-zip

Arch ive fi le s are u s u ally cre ate d w i th a .7z e x te n s i o n

C re ati n g an arch ive : (a: ad d )

7z a <archive> <files or directories>

L i s t fi le s i n arch ive : (l: li s t)

7z l <archive>

E xtracti n g fro m a 7-z i p arch ive : (e: e x tract)

7z x <archive>

Backup a directory (keeping owner and group information):tar cf ­ <dir> | 7z a ­si dir.tar.7z

Restore this backup:7z x ­so dir.tar.7z | tar xf ­

standard input

standard output

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Checking file integrity

Very low cost solution to check file integrity

md5sum FC3­i386­disk*.iso > MD5SUMComputes a MD5 (Message Digest Algorithm 5) 128 bit checksum of the given files. Usually redirected to a file.

Example output:db8c7254beeb4f6b891d1ed3f689b412 FC3­i386­disc1.iso2c11674cf429fe570445afd9d5ff564e FC3­i386­disc2.isof88f6ab5947ca41f3cf31db04487279b FC3­i386­disc3.iso6331c00aa3e8c088cc365eeb7ef230ea FC3­i386­disc4.iso

md5sum ­c MD5SUMChecks the integrity of the files in MD5SUM by comparing their actual MD5 checksum with their original one.

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The Unix and GNU / Linux command line

MiscellaneousPrinting

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Unix printing

M u lti -u s e r, m u lti -jo b , m u lti -c li e n t, m u lti -p ri n te r

I n U n i x / L i n u x , p ri n ti n g co m m an d s d o n 't re ally

p ri n t. T h e y s e n d jo b s to p ri n ti n g q u e u e s , p o s s i b ly

o n th e lo cal m ach i n e , o n n e tw o rk p ri n ti n g s e rve rs

o r o n n e tw o rk p ri n te rs .

Pri n te r i n d e p e n d e n t s ys te m :

Pri n t s e rve rs o n ly acce p t jo b s i n Po s tS cri p t

o r te x t. Pri n te r d rive rs o n th e s e rve r tak e

care o f th e co n ve rs i o n to e ach p ri n te rs o w n fo rm at.

R o b u s t s ys te m :

R e b o o t a s ys te m , i t w i ll co n ti n u e to p ri n t p e n d i n g

jo b s .

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Printing commands

U se fu l e n vi ro n m e n t variab le : PRINTERS e ts th e d e fau lt p ri n te r o n th e sys te m . E x am p le :

export PRINTER=lp

lpr [­P<queue>] <files>S e n d s th e g ive n fi le s to th e s p e c i fi e d p ri n ti n g q u e u e

T h e fi le s m u s t b e i n te x t o r Po s tS cri p t fo rm at.

O th e rw i s e , yo u o n ly p ri n t g arb ag e .

a2ps [­P<queue>] <files>“An y to Po s tS cri p t” co n ve rts m an y fo rm ats to

Po s tS cri p t an d s e n d th e o u tp u t to th e s p e c i fi e d

q u e u e . U s e fu l fe atu re s : s e ve ral p ag e s / s h e e t, p ag e

n u m b e ri n g , i n fo fram e ...

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Print job control

lpq [­P<queue>]Lists all the print jobs in the given or default queue.

lp is not readyRank    Owner   Job     File(s)                         Total Size1st     asloane 84      nsa_windows_backdoors.ps        60416 bytes2nd     amoore  85      gw_bush_iraq_mistakes.ps        65024000 bytes

cancel <job#> [<queue>]Removes the given job number from the default queue.

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Using PostScript and PDF files

Vie w in g a Po s tS cri p t fi le

Po s tS cri p t vi e w e rs e x i s t, b u t th e i r q u ali ty i s p re tty

p o o r.

B e tte r co n ve rt to PD F w i th ps2pdf:

ps2pdf decss_algorithm.psxpdf decss_algorithm.pdf &

Prin ti n g a PD F fi le

Yo u d o n 't n e e d to o p e n a PD F re ad e r!

B e tte r co n ve rt to Po s tS cri p t w i th pdf2ps:

pdf2ps rambaldi_artifacts_for_dummies.pdflpr rambaldi_artifacts_for_dummies.ps

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The Unix and GNU / Linux command line

MiscellaneousComparing Files and Directories

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Comparing files and directories

diff file1 file2R e p o rts th e d i ffe re n ce s b e tw e e n 2 fi le s , o r

n o th in g i f th e fi le s are i d e n ti cal.

diff ­r dir1/ dir2/R e p o rts all th e d i ffe re n c e s b e tw e e n fi le s w i th

th e sam e n am e i n th e 2 d i re c to ri e s .

T o i n ve s tig ate d i ffe re n c e s i n d e tai l, b e tte r u s e

g rap h i cal to o ls !

vim d i ff

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vimdiffvimdiff file1 file2

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meld

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kdiffAn o th e r n i c e to o l to co m p are fi le s an d m e rg e

d i ffe re n ce s

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gvimdiffAn o th e r n i c e to o l to vi e w d i ffe re n ce s i n

fi le s

Available in most distributions with gvimApparently not using diff.No issue with files with binary sections!

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The Unix and GNU / Linux command line

MiscellaneousLooking for Files

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The find command

B e tte r e x p lain e d b y a fe w e xam p le s !

find . ­name “*.pdf”L i s ts all th e *.pdf fi le s i n th e c u rre n t (.)

d i re c to ry o r s u b d i re c to ri e s . Yo u n e e d th e

d o u b le q u o te s to p re ve n t th e s h e ll fro m

e x p an d in g th e * c h aracte r.

find docs ­name "*.pdf" ­exec xpdf {} ';'F in d s all th e *.pdf fi le s i n th e docs d i re c to ry

an d d i s p lays o n e afte r th e o th e r.

M an y m o re p o s s i b i li ti e s avai lab le ! H o w e ve r,

th e ab o ve 2 e xam p le s c o ve r m o s t n e e d s .

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The locate commandM u ch fas te r re g u lar e x p re s s i o n s e arch alte rn ative

to find

locate keysLists all the files on your system with keys in their name.

locate “*.pdf”L i s ts all th e *.pdf fi le s avai lab le o n th e w h o le

m ach i n e

locate “/home/fridgevuhung/*

eer*”Lists all the *beer* files in the given directory (absolute

p ath )

locate i s m u ch fas te r b e cau s e i t i n d e x e s all fi le s i n

a d e d i cate d d atab as e , w h i ch i s u p d ate d o n a

re g u lar b as i s .

updatedb

find i s b e tte r to s e arch th ro u g h re ce n tly cre ate d

fi le s .

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The Unix and GNU / Linux command line

MiscellaneousVarious Commands

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Getting information about users

whoL i s ts all th e u s e rs lo g g e d o n th e s ys te m .

whoamiT e lls w h at u s e r I am lo g g e d as .

groupsT e lls w h i ch g ro u p s I b e lo n g to .

groups <user>T e lls w h i ch g ro u p s <user> b e lo n g s to .

finger <user>T e lls m o re d e tai ls (re al n am e , e tc ) ab o u t <user>D i sab le d i n s o m e s ys te m s (s e cu ri ty re aso n s ).

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Changing users

Yo u d o n o t h ave to lo g o u t to lo g o n an o th e r

u s e r acco u n t!

su vuhung(R are ) C h an g e to th e hyde acco u n t, b u t

k e e p i n g th e e n vi ro n m e n t variab le s e tti n g s

o f th e o rig i n al u s e r.

su ­ vuhung(M o re fre q u e n t) L o g o n th e jekyll acco u n t,

w i th e xactly th e sam e s e tti n g s as th i s n e w

u s e r.

su ­W h e n n o arg u m e n t i s g ive n , i t m e an s th e

root u s e r.

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The wget command

I n s te ad o f d o w n lo ad i n g fi le s fro m yo u r b ro w s e r,

ju s t co p y an d p as te th e i r U R L an d d o w n lo ad th e m

w i th wget!

wget m ai n fe atu re s

h ttp an d ftp s u p p o rt

C an re s u m e i n te rru p te d d o w n lo ad s

C an d o w n lo ad e n ti re s i te s o r at le as t c h e ck fo r b ad

li n k s

Ve ry u s e fu l i n s cri p ts o r w h e n n o g rap h i c s are

avai lab le

(sys te m ad m in i s trati o n , e m b e d d e d sys te m s )

Pro x y s u p p o rt (http_proxy an d ftp_proxy e n v.

(s e t) variab le s )

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wget examples

wget ­c \ http://microsoft.com/customers/dogs/winxp4dogs.zipContinues an interrupted download.

wget ­m https://www.facebook.com/nguyenvuhungMirrors a site.

wget ­r ­np http://virror.hanoilug.org/Recursively downloads an on­line book for off­line access.­np: "no­parent". Only follows links in the current directory.

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Misc commands (1)

sleep 60W aits fo r 60 s e co n d s

(d o e s n 't co n s u m e sys te m re s o u rce s ).

wc report.txt (word count)438  2115 18302 report.txtC o u n ts th e n u m b e r o f li n e s , w o rd s an d

ch aracte rs i n a fi le o r i n s tan d ard i n p u t.

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Misc commands (2)

bc ("basic calculator?")bc is a handy but full­featured calculator. Even includes a programming language! Use the ­l option to have floating point support.

python as a calculator

dateR e tu rn s th e c u rre n t d ate . U s e fu l i n s cri p ts

to re co rd w h e n co m m an d s s tarte d o r

co m p le te d .

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The Unix and GNU/Linux command line

System Administration Basics

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File ownership

Parti cu larly u s e fu l i n (e m b e d d e d ) sys te m

d e ve lo p m e n t

w h e n yo u cre ate fi le s fo r an o th e r s ys te m .

chown ­R vuhung /home/linux/src (­R: recursive)M ak e s u s e r vuhung th e n e w o w n e r o f all th e fi le s i n

/home/linux/src. 

chgrp ­R core /home/vuhungM ak e s core th e n e w g ro u p o f e ve ryth i n g i n

/home/vuhung.

chown ­R vuhung:core /FileServer/Backup/chown can b e u s e d to ch an g e th e o w n e r an d g ro u p

at th e sam e tim e .

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Shutting down

shutdown ­h +5 (­h: halt)S h u ts th e sys te m d o w n i n 5 m i n u te s .

U s e rs g e t a w arn i n g i n th e i r co n s o le s .

shutdown ­h now (0)

shutdown ­r now (­r: re b o o t)

init 0Another way to shutdown(init is used internally by shutdown).

init 6Another way to reboot.

[Ctrl][Alt][Del]Also works on GNU/Linux (at least on PCs!).

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Network setup (1)

/sbin/ifconfig ­a; echo $PATHPrin ts d e tai ls ab o u t all th e n e tw o rk i n te rface s

avai lab le o n yo u r sys te m .

ifconfig eth0L i s ts d e tai ls ab o u t th e eth0 i n te rface

ifconfig eth0 192.168.52.100Ass ig n s th e 192.168.52.100 I P ad d re s s

to eth0 (1 I P ad d re s s p e r i n te rface ).

ifconfig eth0 downS h u ts d o w n th e eth0 i n te rface

(fre e s i ts I P ad d re s s ).

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Network setup (2)

route add default gw 192.168.52.3S e ts th e d e fau lt ro u te fo r p ack e ts o u ts i d e th e

lo cal n e tw o rk . T h e g ate w ay (h e re

192.168.52.3) i s re s p o n s i b le fo r s e n d i n g th e m

to th e n e x t g ate w ay, e tc ., u n ti l th e fi n al

d e s ti n ati o n .

routeL i s ts th e e x i s ti n g ro u te s

route del defaultroute del <IP>D e le te s th e g ive n ro u te

U s e fu l to re d e fi n e a n e w ro u te .

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Network testingping freshmeat.net (external)

ping 192.168.52.16 (internal)ping 192.168.51.1 (semi­internal)T ri e s to s e n d p ack e ts to th e g ive n m ach i n e an d g e t

ack n o w le d g m e n t p ack e ts i n re tu rn .

PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.64 bytes from 192.168.51.1: icmp_seq=0 ttl=150 time=2.51 ms64 bytes from 192.168.51.1: icmp_seq=1 ttl=150 time=3.16 ms64 bytes from 192.168.51.1: icmp_seq=2 ttl=150 time=2.71 ms64 bytes from 192.168.51.1: icmp_seq=3 ttl=150 time=2.67 ms

W h e n yo u can p i n g yo u r g ate w ay, yo u r n e tw o rk

i n te rface w o rk s fi n e .

W h e n yo u can p i n g an e x te rn al I P ad d re s s , yo u r

n e tw o rk s e tti n g s are co rre ct!

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Network setup summary

O n ly fo r s im p le cas e s w i th 1 i n te rface , n o d h cp

s e rve r...

C o n n e c t to th e n e tw o rk (cab le , w ire le s s card o r

d e vi c e ...)

I d e n ti fy yo u r n e tw o rk i n te rface :

ifconfig ­a

Ass ig n an I P ad d re s s to yo u r i n te rface

(as s u m in g eth0)

ifconfig eth0 192.168.52.100 (e xam p le )

Ad d a ro u te to yo u r g ate w ay (as s u m in g

192.168.52.3) fo r p ack e ts o u ts i d e th e n e tw o rk :

route add default gw 192.168.52.3

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Name resolution

Yo u r p ro g ram s n e e d to k n o w w h at I P ad d re s s

co rre s p o n d s to a g ive n h o s t n am e (s u ch as

kernel.org)

D o m ain N am e S e rve rs (D N S ) tak e care o f th i s .

Yo u ju s t h ave to s p e c i fy th e I P ad d re s s o f 1 o r

m o re D N S s e rve rs i n yo u r /etc/resolv.conf

fi le :

nameserver 192.168.52.3 (Internal DNS server)nameserver 8.8.8.8 (Google Open DNS)

nameserver 8.8.4.4 (Google Open DNS)

nameserver 203.162.4.190 (Viettel)

T h e c h an g e s tak e s e ffe c t im m e d iate ly!

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Creating filesystems

E xam p le s

mkfs.ext2 /dev/sda1F orm ats yo u r U S B k e y (/dev/sda1: 1

s t p arti ti o n raw

d ata) i n ext2 fo rm at.

mkfs.ext2 ­F disk.imgF orm ats a d i s k im ag e fi le i n e x t2 fo rm at

mkfs.vfat ­v ­F 32 /dev/sda1 (­v: ve rb o s e )

F orm ats yo u r U S B k e y b ack to F AT 32 fo rm at.

mkfs.vfat ­v ­F 32 disk.imgF orm ats a d i s k im ag e fi le i n F AT 32 fo rm at.

B lan k d i s k im ag e s can b e cre ate d as i n th e b e lo w

e xam p le :

dd if=/dev/zero of=disk.img bs=1024 count=65536

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Mounting devices (1)

T o m ak e fi le sys te m s o n an y d e vi c e

(i n te rn al o r e x te rn al s to rag e )

vi s i b le o n yo u r sys te m , yo u h ave to m ount th e m .

T h e fi rs t tim e , cre ate a m o u n t p o i n t i n yo u r s ys te m :

mkdir /mnt/usbdisk (e x am p le )

N o w , m o u n t i t:

mount ­t vfat /dev/sda1 /mnt/usbdisk/dev/sda1: physical device­t: specifies the filesystem (format) type(ext2, ext3, vfat, reiserfs, iso9660...)

raw data(file descriptors

and file contents)

mount

filestructure

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Mounting devices (2)L o ts o f mount o p ti o n s are avai lab le , i n p arti cu lar to

ch o o s e p e rm i s s i o n s o r th e fi le o w n e r an d g ro u p ... S e e

th e mount m an u al p ag e fo r d e tai ls .

M o u n t o p ti o n s fo r e ach d e vi c e can b e s to re d i n th e

/etc/fstab fi le .

T h an k s to th i s fi le , yo u ju s t n e e d to s tate th e m o u n t

p o i n t:

# /etc/fstab: static file system information.# <file system> <mount point>   <type>  <options>       <dump> <pass>proc            /proc           proc    defaults        

0       0/dev/hda3       /               ext3    defaults,errors=remount­ro 0       1/dev/hda4       /home           ext3    defaults        

0       2/dev/hda2       /root2          ext3    defaults        

0       2/dev/hda1       none            swap    sw              

0       0/dev/hdc        /media/cdrom0   udf,iso9660 user,noauto     

0       0

mount e xam p le s w i th  /etc/fstab:

mount /procmount /media/cdrom0 

Device list: /proc/partitions

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Mounting devices (3)

Yo u can als o m o u n t a fi le sys te m im ag e

s to re d i n a re g u lar fi le (loop d e vice s)

U s e fu l to d e ve lo p fi le sys te m s fo r an o th e r m ach i n e

U s e fu l to acce s s th e co n te n ts o f an I S O c d ro m

im ag e w i th o u t h avi n g to b u rn i t.

U s e fu l to c re ate a L i n u x p arti ti o n o n a h ard d i s k

w i th o n ly W in d o w s p arti ti o n s

cp /dev/sda1 usbkey.imgmount ­o loop ­t vfat usbkey.img /mnt/usbdisk 

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Listing mounted filesystems

Ju s t u s e th e mount co m m an d w i th n o arg u m e n t:

/dev/hda6 on / type ext3 (rw,noatime)none on /proc type proc (rw,noatime)none on /sys type sysfs (rw)none on /dev/pts type devpts (rw,gid=5,mode=620)usbfs on /proc/bus/usb type usbfs (rw)/dev/hda4 on /data type ext3 (rw,noatime)none on /dev/shm type tmpfs (rw)/dev/hda1 on /win type vfat (rw,uid=501,gid=501)none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)

O r d i s p lay th e /etc/mtab fi le

(sam e re s u lt, u p d ate d b y mount an d umount e ach

tim e th e y are ru n )

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Unmounting devices

umount /mnt/usbdiskC o m m i ts all p e n d i n g w ri te s an d u n m o u n ts th e g ive n

d e vi c e , w h i c h can th e n b e re m o ve d i n a safe w ay.

T o b e ab le to u n m o u n t a d e vi c e , yo u h ave to c lo s e

all th e o p e n fi le s i n i t:

C lo s e ap p li cati o n s o p e n i n g d ata i n th e m o u n te d

p arti ti o n

M ak e s u re th at n o n e o f yo u r s h e lls h ave a w o rk i n g

d i re c to ry i n th i s m o u n t p o in t.

Yo u can ru n th e lsof c o m m an d (li s t o p e n fi le s ) to

vi e w w h i c h p ro ce s s e s s ti ll h ave o p e n fi le s i n th e

m o u n te d p arti ti o n .

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Beware of the dark side of root

root u s e r p rivi le g e s are o n ly n e e d e d fo r ve ry

s p e c i fi c task s w i th s e cu ri ty ri s k s : m o u n ti n g ,

cre ati n g d e vi c e fi le s , lo ad i n g d rive rs , s tarti n g

n e tw o rk i n g ,

ch an g in g fi le o w n e rs h i p , p ack ag e u p g rad e s ...

E ve n i f yo u h ave th e root p as sw o rd , yo u r re g u lar

acco u n t s h o u ld b e s u ffi c i e n t fo r 99.9 % o f yo u r

task s

(u n le s s yo u are a s ys te m ad m in i s trato r).

I n a trai n i n g s e s s i o n , i t i s acc e p tab le to u s e root.

I n re al li fe , yo u m ay n o t e ve n h ave acce s s to th i s

acco u n t, o r p u t yo u r s ys te m s an d d ata at ri s k i f yo u

d o .

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Using the root account

I n cas e you re ally w an t to u s e root...

I f yo u h ave th e root p as sw o rd :

su ­ (s w itch u s e r)

I n m o d e rn d i s tri b u ti o n s , th e sudo co m m an d g ive s yo u

acce s s to s o m e root p ri vi le g e s w i th yo u r o w n u s e r

p as sw o rd .

E xam p le : sudo mount /dev/hda4 /home

D i s tri b u ti o n s li k e D e b ian o r U b u n tu b y d e fau lt d o n 't

allo w th e root u s e r to u s e g rap h i cal ap p li cati o n s (m o re

com p le x an d th u s m o re vu ln e rab le ).

I f yo u re ally w an t to s tart a g rap h i cal ap p li cati o n w i th

root, typ e :

As root: export DISPLAY=:0 (i .e . u s e th e fi rs t d i s p lay)

As yo u r re g u lar u s e r: xhost + (i .e . allo w o th e r u s e rs )

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The Unix and GNU/Linux command line

GNU/Linux: Distribution Packages

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How to find packages

U b u n tu , D e b ian

ap t-cach e s e arch m e ld

h ttp ://w w w .d e b ian .o rg /d i s tri b /p ack ag e s

S e arch b y p ack ag e o r fi le n am e

rp m fi n d : h ttp ://rp m fi n d .n e t/

L o ts o f R PM p ack ag e s fo r R e d H at,

M an d riva, S u s e ...

R e d h at varian ts

yu m s e arch “k e yw o rd ”

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Identifying packages

W h at p ack ag e d o e s a fi le b e lo n g to ?

U se fu l to g e t m o re i n fo rm ati o n , g e t th e co d e ,

fi n d n e w e r ve rs i o n s , re p o rt i s s u e s ...

D i s tri b u ti o n w i th R PM p ack ag e s :

(R e d H at, F e d o ra, M an d riva, S u s e ...)

> rpm ­qf /bin/lscoreutils­5.2.1­7

D e b ian , U b u n tu :

> dpkg ­S /bin/lsfileutils: /bin/ls

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Information about packages

Acce s s p ack ag e d e s cri p ti o n , ve rs i o n n u m b e r,

s o u rc e s , e tc .

R PM b ase d d i s tri b u ti o n s :

rpm ­qi <package­name>

D e b ian :

dpkg ­s <package­name>

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The Unix and GNU/Linux command line

Going Further

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Command help

S o m e U n i x c o m m an d s an d m o s t G N U / L i n u x

co m m an d s o ffe r at le as t o n e h e lp arg u m e n t:

­h(­ i s m o s tly u s e d to i n tro d u ce 1 -ch aracte r

o p ti o n s )

­­help(­­ i s alw ays u s e d to i n tro d u c e th e

co rre s p o n d i n g “lo n g ” o p ti o n n am e , w h i c h

m ak e s s c ri p ts e as i e r to u n d e rs tan d )

Yo u als o o fte n g e t a s h o rt s u m m ary o f o p ti o n s

w h e n yo u i n p u t an i n vali d arg u m e n t.

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Manual pages

man <keyword>D i s p lays o n e o r s e ve ral m an u al p ag e s fo r

<keyword>

man man

M o st avai lab le m an u al p ag e s are ab o u t U n i x

c o m m an d s , b u t s o m e are als o ab o u t C fu n c ti o n s ,

h e ad e rs o r d ata s tru ctu re s , o r e ve n ab o u t s ys te m

co n fi g u rati o n fi le s !

man stdio.h

man fstab (for /etc/fstab)

M an u al p ag e fi le s are lo o k e d fo r i n th e d i re cto ri e s

s p e c i fi e d b y th e MANPATH e n vi ro n m e n t variab le .

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Info pages

I n G N U , m an p ag e s are b e i n g re p lace d b y i n fo

p ag e s . S o m e m an u al p ag e s e ve n te ll to re fe r to

i n fo p ag e s i n s te ad .

info <command>

info fe atu re s :

D ocu m e n tati o n s tru ctu re d i n s e c ti o n s

(“n o d e s ”) an d s u b s e c ti o n s (“s u b n o d e s ”)

Po s s i b i li ty to n avig ate i n th i s s tru ctu re : to p ,

n e x t, p re v, u p

I n fo p ag e s g e n e rate d fro m th e sam e te x i n fo

s o u rce as th e H T M L d o cu m e n tati o n p ag e s

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Searching the Internet for resources (1)

I n ve s ti g ati n g i s s u e s

M o s t fo ru m s an d m ai li n g li s t arch ive s are

p u b li c , an d are i n d e x e d o n a ve ry fre q u e n t

b as i s b y G o o g le .

I f yo u i n ve s ti g ate an e rro r m e s sag e , co p y i t

ve rb atim i n th e s e arch fo rm , e n c lo s e d i n d o u b le

q u o te s (“e rro r m e s sag e ”). L o ts o f c h an ce s th at

s o m e b o d y e ls e alre ad y face d th e sam e i s s u e .

D o n 't fo rg e t to u s e G o o g le G ro u p s :

h ttp ://g ro u p s .g o o g le .c o m /

T h i s s i te i n d e x e s m o re th an 2 0 ye ars o f

n e w sg ro u p s m e s sag e s .

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Searching the Internet for resources (2)

L o o k i n g fo r d o cu m e n tati o n

L o o k fo r <tool> o r <tool> page to fi n d th e to o l o r

p ro je ct h o m e p ag e an d th e n fi n d th e late s t

d o cu m e n tati o n re s o u rce s .

L o o k fo r <tool> documentation o r <tool> manual

i n yo u r favo ri te s e arch e n g i n e .

L o o k i n g fo r g e n e ri c te ch n i cal

i n fo rm ati o n

W ik iPe d ia: h ttp ://w ik i p e d ia.o rg

L o ts o f u s e fu l d e fi n i ti o n s i n co m p u te r s c i e n c e . A

re al e n cyclo p e d ia! O p e n to an yo n e 's c o n tri b u ti o n s .

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Local Communities

Vie tlu g

U b u n tu -vn

H an o iL u g

S aig o n L u g

H u e L u g

T h aiN g u ye n L U G

D an an g L u g ?

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I n tro d u cti o n to G N U /L in u x an d F re e S o ftw are

L i n u x an d e co lo g y

W h at's n e w i n L i n u x 2 .6?

H o w to p o rt L i n u x o n a n e w PD A

M o re th an 1 5 00 p ag e s u n d e r fre e li c e n s e s .

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LAMP BasicC e n tO S

yu m i n s tall h ttp d m ysq l-s e rve r p h p

yu m i n s tall h ttp d -d e ve l m ysq l-d e ve l p h p -d e ve l

U b u n tu

ap t-g e t i n s tall ap ach e 2 p h p 5 -m ysq l li b ap ach e 2 -

m o d -p h p 5 m ysq l-s e rve r

su d o /e tc/in i t.d /ap ach e 2 re s tart

su d o /e tc/in i t.d /h ttp d s tart|re s tart|s to p

s u d o /e tc/in i t.d /m ysq ld s tart|re s tart|s to p

Ad d i ti o n p ack ag e s : p h p -co m m o n p h p -g d p h p -

m cryp t p h p -p e ar p h p -p e c l-m e m cach e p h p -

m h ash p h p -m ysq l p h p -xm l

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Further Readings

h ttp ://arti c le s .s li c e h o s t.c o m /2 008/2 /6/

ce n to s -i n s talli n g -ap ach e -an d -p h p 5

h ttp ://tld p .o rg /L D P/sag /h tm l/i n d e x .h t

m l

An y b o o k s o n L AM P

Q&A

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Rights to copyA t tr ibu t ion – S hareA l ike 2 .5You are free

to co p y, d i s tri b u te , d i s p lay, an d p e rfo rm th e

w o rk

to m ak e d e rivative w o rk s

to m ak e com m e rc ial u s e o f th e w o rk

U nder the fol lowing c ondi t ionsA t t r ibu t ion . You m u s t g i ve th e

o ri g i n al au th or cre d i t.

S hare A l ike . I f yo u alte r, tran sform ,

o r b u i ld u p on th i s w o rk , yo u m ay

d i s tri b u te th e re su lti n g w ork o n ly

u n d e r a li c e n se i d e n ti cal to th i s o n e .

F or an y re u se o r d i s tri b u ti o n , yo u m u st m ak e

c le ar to o th e rs th e li c e n se te rm s o f th i s

w o rk .

An y o f th e se co n d i ti o n s can b e w aive d i f you

g e t p e rm i s s i o n from th e cop yrig h t h o ld e r.

You r fai r u se and other r ights are in no way affec ted by the above.

L i c e n s e te x t:

h ttp ://cre ative co m m o n s .o rg /li c e n s e s/b y-sa/2 .5 /le g alco d e

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