How Linux Works: What Every Super-User Should Know by Brian

350 Pages·2005·5.22 MB·English

How Linux Works: What Every Super-User Should Know
by Brian Ward ISBN:1593270356
No Starch Press © 2004 (347 pages)
This guide describes the inner workings of a Linux system beginning with the file system and boot process and
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
Table of Contents
How Linux Works—What Every Super-User Should Know
Chapter 1 -The Basics
Chapter 2 -Devices, Disks, Filesystems, and the Kernel
Chapter 3 -How Linux Boots
Chapter 4 -Essential System Files, Servers, and Utilities
Chapter 5 -Configuring Your Network
Chapter 6 -Network Services
Chapter 7 -Introduction to Shell Scripts
Chapter 8 -Development Tools
Chapter 9 -Compiling Software From Source Code
Chapter 10 -Maintaining the Kernel
Chapter 11 -Configuring and Manipulating Peripheral Devices
Chapter 12 -Printing
Chapter 13 -Backups
Chapter 14 -Sharing Files with Samba
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Appendix A-Command Classification
Bibliography
Index
List of Figures
List of Tables
List of Sidebars
Back Cover
How Linux Works: What Every Super-User Should Know
Whether you’re a systems administrator or a home user, you need to understand how Linux internals work before you can really
by Brian Ward ISBN:1593270356
master Linux—how it boots, how networking works, how to customize the kernel, and even what hardware to buy.
No Starch Press © 2004 (347 pages)
How Linux WorksT hcoisn gtauiindse tdhees kcrinibde so ft hinef oinrmneart iwonor nkionrgmsa ollfy a h Lainnduexd s dyostwenm f rboemgi nwniiznagr dws—ithk nthoew lfeildeg sey sthteamt c aonmde bs oforot mpr yoeceasrss aonfd
experience doingc tohvienrgins gt haed vhaanrdce wda tyo.p Bicust siuncshte aasd noef tsweoerkkiningg ,t hfier erwigahltl si,n dceanvetalotipomn etnot mtoaokles, ydoeuvri csey smteamna wgeomrke, nyto, us hcealnl srceraidpt sH, oawnd
Linux Works to ssehea hrionwg tpor iandtemrsin wisittehr SLainmubxa a.nd why each particular technique works. This book covers such need-to-know topics
as:
Table of Contents
How Linux boots, with coverage of boot loaders and init
How Linux Works—What Every Super-User Should Know
ChaptHeor w1 ne-tTwhoer kBinagsi,c isnterfaces, firewalls, and servers work
Chapter 2 -Devices, Disks, Filesystems, and the Kernel
How development tools and shared libraries work
Chapter 3 -How Linux Boots
ChaptHeor w4 th-eE ksesrennetli aml Sanysatgeems dFeilveisc,e Ss,e rdveevrisc,e adnrdiv Uertsil,i taiensd processes, and how to build a custom kernel
ChaptHeor w5 th-eC Loinnufixg uprriinngt inYgo usry sNteetmw owrkorks, with sections on cups, filters, and Ghostscript
Chapter 6 -Network Services
How shell scripts work
Chapter 7 -Introduction to Shell Scripts
WCihtha pittse rc 8omb-iDnaetvioelno pomf beanctk Tgoroolusnd theory and real-world examples, How Linux Works will show you how to run your system
inCshtaepatde ro f9 ha-viCnogm ypoiulirn gsy Sstoeftmw aruren Fyrooum. Source Code
Chapter 10 -Maintaining the Kernel
About the Author
Chapter 11 -Configuring and Manipulating Peripheral Devices
BCrhiaanp tWera r1d2 h-aPs rbineteinng working with Linux since 1993, when he scraped together enough pennies for a secondhand 386. He has a
PChh.Dap. tienr c1o3m-puBtaecrk sucpiesnce from the University of Chicago and currently lives in San Francisco. He is the author of the Linux Kernel
HOWTO, The Book of VMware (No Starch Press), and The Linux Problem Solver (No Starch Press).
Chapter 14 -Sharing Files with Samba
Chapter 15 -Network File Transfer

Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Appendix A-Command Classification
Bibliography
Index
List of Figures
List of Tables
List of Sidebars
How LHionwu Lixnux WWoroksr: Wkhsat— EveWry Shupear-tU sEer Svheourldy K nSowuper-User Should
by Brian Ward ISBN:1593270356
Know No Starch Press © 2004 (347 pages)
This guide describes the inner workings of a Linux system beginning with the file system and boot process and
by Brian Wacorvdering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
Table of Contents
How Linux Works—What Every Super-User Should Know
Chapter 1 -The Basics
Chapter 2 -Devices, Disks, Filesystems, and the Kernel
ChNaOpt eSr T3AR-CHoHw PLiRnuExS BSoots
ChSaapnte rF 4ran-cEisssceontial System Files, Servers, and Utilities
Chapter 5 -Configuring Your Network
ChCaoppteyr r6igh-t N©e t2w0o0rk4 S beyrv Bicerisan Ward.
Chapter 7 -Introduction to Shell Scripts
Chapter 8 -Development Tools
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means,
Chapter 9 -Compiling Software From Source Code
electronic or mechanical, including photocopying, recording, or by any information storage or retrieval
Chapter 10 -Maintaining the Kernel
system, without the prior written permission of the copyright owner and the publisher.
Chapter 11 -Configuring and Manipulating Peripheral Devices
Chapter 12 -Printing
Chapte Pr 1ri3nt-eBda coknu prescycled paper in the United States of America
Chapter 14 -Sharing Files with Samba
Ch1a p2t e3r 415 5- 6N e7t w8o 9rk 1 F0il e- T0r7an 0sf6e r05 04
Chapter 16 -User Environments
No Starch Press and the No Starch Press logo are registered trademarks of No Starch Press, Inc. Linux is
Chapter 17 -Buying Hardware for Linux
a registered trademark of Linus Torvalds. Other product and company names mentioned herein may be
Chapter 18 -Further Directions
the trademarks of their respective owners. Rather than use a trademark symbol with every occurrence of a
Appendix A-Command Classification
trademarked name, we are using the names only in an editorial fashion and to the benefit of the trademark
Bibliography
owner, with no intention of infringement of the trademark.
Index
List of Figures
Publisher: William Pollock
List of Tables
List of Sidebars
Managing Editor: Karol Jurado
Cover and Interior Design: Octopod Studios
Technical Reviewer: Scott Schwartz
Copyeditor: Andy Carroll
Compositor: Wedobooks
Proofreader: Stephanie Provines
Indexer: Brian Ward
For information on book distributors or translations, please contact No Starch Press, Inc. directly:
No Starch Press, Inc.
555 De Haro Street, Suite 250, San Francisco, CA 94107
phone: [phone]; fax: [phone]; <[email protected];> http://www.nostarch.com
The information in this book is distributed on an "As Is" basis, without warranty. While every precaution
has been taken in the preparation of this work, neither the author nor No Starch Press, Inc. shall have any
liability to any person or entity with respect to any loss or damage caused or alleged to be caused directly
or indirectly by the information contained in it.
Library of Congress Cataloguing-in-Publication Data
Ward, Brian.
How Linux works : what every super-user should know / Brian Ward.
p. cm.
Includes index.
ISBN 1-59327-035-6
1. Linux. 2. Operating systems (Computers). I. Title.
How Linux Works: What Every Super-User Should Know
by Brian Ward ISBN:1593270356
QA76.76.O63 W3654 2004
No Starch Press © 2004 (347 pages)
005.4'32-T-hdisc g2u2ide describes the inner workings of a Linux system beginning with the file system and boot process and
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
2004002692
Table of Contents
How Linux Works—What Every Super-User Should Know
Chapter 1 -The Basics
Chapter 2 -Devices, Disks, Filesystems, and the Kernel
Chapter 3 -How Linux Boots
Chapter 4 -Essential System Files, Servers, and Utilities
Chapter 5 -Configuring Your Network
Chapter 6 -Network Services
Chapter 7 -Introduction to Shell Scripts
Chapter 8 -Development Tools
Chapter 9 -Compiling Software From Source Code
Chapter 10 -Maintaining the Kernel
Chapter 11 -Configuring and Manipulating Peripheral Devices
Chapter 12 -Printing
Chapter 13 -Backups
Chapter 14 -Sharing Files with Samba
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Appendix A-Command Classification
Bibliography
Index
List of Figures
List of Tables
List of Sidebars
ChapteHorw 1Lin:u xT Whoreks : BWhaat sEviecry sSuper-User Should Know
by Brian Ward ISBN:1593270356
No Starch Press © 2004 (347 pages)
OverviewThis guide describes the inner workings of a Linux system beginning with the file system and boot process and
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
This chapter is a guide to the Unix commands and utilities that you must know to get anything out of this
book. This is preliminary material, and you may already know a substantial amount. Even if you think
Table of Contents
you're up to speed, though, take a few seconds to flip through the sections just to make sure.
How Linux Works—What Every Super-User Should Know
ChYaopute rm 1ay- bTehe a Bsaksiincgs yourself, "I thought this was a book about Linux, not Unix?" Don't worry; this chapter is
Chjuasptt egr e2ttin-gD eyvoicue sr,e Daidskys ,f oFril ewsoysrtkeimngs, wanitdh ththee K Lerinneulx system. Linux is a Unix flavor at heart. You will see the
Chwaoprtedr "3Un-ixH"o iwn Ltihniusx cBhoaoptster more than "Linux" because you can take the information straight over to
ChSaopltaerr i4s, B-SEsDse, natniadl Soytshteemr UFinleixs,- fSlaervvoerrse,d a nsdy sUtteilmitiess. Special care has been taken to avoid too many Linux-
Chsappetecri f5ic u-sCeorn ifnigtuerrinfagc Yeo uerx Nteetnwsoiorkns, not only so you will have a better background with other operating
Chsaypstteer m6s,- bNuett waolsrko Sbeervciaceusse these extensions tend to be extremely unstable. You will be able to adapt to
Chnaepwte rL 7inu-xI nretrloedauscetiso nm tou cShhe mll Socrreip qtsuickly if you know the core that does not change.
Chapter 8 -Development Tools
ChAalpthteor u9gh- tChoem mpialinteg rSiaolf thwearree Fmroamy Ssoeuermce Cspodaerse, you need to convince yourself that Unix is not hard. Yes,
Chmapotsetr r1e0p-orMtsai nfrtaoimnin tgh teh efi eKledrn aerle to the contrary, but in the end, Unix is nothing but a bunch of files and a few
Chcaopmtemr 1a1nd-sC ofnofrig murainngi paundla Mtianngi ptuhloatsineg f iPleersip. hIef ryaol Due avircee sfamiliar with other operating systems, you shouldn't
Chhaapvteer a1 2pr-oPbrilnetming. However, if you find the information in this preliminary chapter somewhat lacking, there
Chaarpet ebro 1o3ks- Bwaictkhu pmsuch more detail for beginners, such as UNIX for the Impatient [Abrahams] and Learning
Chthapet eUr N14IX- OShpaerirnagti nFigle sS wysithte Smam [Pbaeek].
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Appendix A-Command Classification
Bibliography
Index
List of Figures
List of Tables
List of Sidebars
1.1A bouHto w/b Liinnu/xs Whorks: What Every Super-User Should Know
by Brian Ward ISBN:1593270356
The shell is Noon eS toarfc thh Per emsso ©s t2 0im04 p(3o4r7t paanget sp)arts of a Unix system. A shell is a program that runs commands.
For exampleT,h oisn geu iodef tdheesc srihbeesll 'tsh ed iuntnieers wiso rtkoin rgusn o tf hae L icnoumx smysatenmds b ethgaintn uinsge wrsit hty tphee .f iSleh seylsltse mal saon ds beorovte p arosc essms aanlld
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
programming environments. Unix programmers often break common tasks into little components and rely
sharing printers with Samba.
on the shell to manage tasks and to piece things together.
TaMblea noyf Cimonptoerntatsnt parts of the system are actually shell scripts — text files that contain nothing but shell
Hocwo mLinmuax nWdosr.k sIf— yWohua ht aEvveer yw Sourpkeer-dU sweirt hS hMouSld-D KOnoSw, shell scripts may seem similar to .BAT files, but the shell is
Chfaapr tmer o1re -pTohwe eBrafsuilc.s Chapter 7 is a small guide to shell scripts, and you can peruse it anytime after finishing
Chthapist ecr h2ap-teDre.vices, Disks, Filesystems, and the Kernel
Chapter 3 -How Linux Boots
ChAasp tyeor u4 pr-oEgssreenstsia tlh Sryosutegmh Fthileiss ,b Soeorvke,r sy,o aun dw Uillt illietiaersn how to manipulate commands with the shell. One of the
Chbaepstet rt h5ing-sC oanbfioguurt inthge Y osuhre Nlle itsw othrkat if you make a mistake, you can look at what you typed, see what went
Chwarpotenrg 6, an-dN etthweonrk t rSye ravgicaesin quickly. Do not be afraid to try new things. The only way to learn the shell is to
Chuaspete irt .7 -Introduction to Shell Scripts
Chapter 8 -Development Tools
ChTahpeterre 9 are- Cmomanpyili ndgi fSfeorftewnatr eU Fnrioxm s hSoeullrsc,e bCuotd eall derive many of their features from the Bourne shell, or
Ch/abpitenr /1s0h-. MEavinetaryin iUngn itxh es yKserteneml needs the Bourne shell to function correctly, as you will see throughout this
Chbaopotekr. 11 -Configuring and Manipulating Peripheral Devices
Chapter 12 -Printing
Linux uses an enhanced version of this shell, called bash, or the "Bourne-again" shell. bash is the default
Chapter 13 -Backups
shell for most Linux distributions, and /bin/sh is normally some sort of link to bash on a Linux system.
Chapter 14 -Sharing Files with Samba
You should use the bash shell when running the examples in this book.
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
You may not have bash if you're using this chapter as a guide for a Unix account at an organization where
Chapter 17 -Buying Hardware for Linux
you are not the systems administrator. You can change your shell with chsh or ask your systems
Chapter 18 -Further Directions
administrator for help.
Appendix A-Command Classification
Bibliography

Index
List of Figures
List of Tables
List of Sidebars
1.2U singHo wth Leinu Sx Whoerklsl: What Every Super-User Should Know
by Brian Ward ISBN:1593270356
When you inNsot aSltlaerdc hL Pinreusxs, © y 2o0u04 s(3e4t7 upapg eas) root (superuser) password, and hopefully you also made at least
one more reTghuisla gru uidsee dre fsocrr ibyeosu trhsee ilnf.n Fero wr othrkiisn gcsh oafp at eLrin, uyxo suy sstheomu bldeg liongni ning wasit ht hthee r feilge uslyasrt eums earn.d boot process and
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
The first thing you need to do after logging in is to bring up a shell window. After starting a shell, its window
contains a prompt at the top that usually ends with a dollar sign ($). On Red Hat Linux, the prompt looks
Talbiklee [ofn Caomnet@enhtosst path]$. If you know Windows, you will find that the shell window looks vaguely similar
Hotow tLhineu cx oWmormksa—nWd hparto Emveprty. Super-User Should Know
Chapter 1 -The Basics
ChapteNr o2te- YDoevuic mesa, yD ihskesa, rF itlhesey ssthemelsl , wainndd tohwe Kreerfneerlred to as the terminal window. The terminal window is the
Chapter 3 -pHaorwt Loifn uthx eB ouostesr interface that accepts keystrokes from the windowing system and draws the
Chapter 4 -cEhssaernatciatle Srsys otenm t hFiele ss,c Sreeervne.r sY, oanud c Uatnili ttihesink of the terminal as a middleman between the shell and
Chapter 5 -tChoen fuigsuerrin.g Your Network
Chapter 6 -Network Services
ChNaopwte rt y7pe- tIhnter ofdoullcotiwonin tgo cShoemll mScarinpdts and press ENTER:
Chapter 8 -Development Tools
Chcaaptte r /9et-cC/opmapsilisngw dSoftware From Source Code
Chapter 10 -Maintaining the Kernel
Chapter 11 -Configuring and Manipulating Peripheral Devices
ChTahpete cr o12m-mParinntdin pgrints a couple of lines that start with usernames, and then you get your shell prompt back.
ChIfa pytoeur 1c3an-'Bt arcekaudp sthe text very well, manipulate the font settings to your liking. You're going to be spending
Chaa pgtoeor d14 pa-rSth oarf inygo uFirle tsim weith w Siathm tbhais book in the shell, so you should be comfortable with it.
Chapter 15 -Network File Transfer
ChTahpete cr a1t6 c-oUmsemr Eannvdir oinsm ae gntrseat one to start with because it's one of the easiest Unix commands. Its syntax is
Chaasp tfeorl l1o7w-s:Buying Hardware for Linux
Chapter 18 -Further Directions
Apcpaetnd fixi lAe-1C ofmimlaen2d C.la.ss.ification
Bibliography
Index
LiWst ohfe Fnig yuoreus run this command, cat prints (and concatenates) the contents of file1,f ile2, and any
Liastd odf itTiaobnleasl files you desire (denoted by ...) and exits.
List of Sidebars
If you do not specify any input files, cat reads from the standard input, which in this case is the keyboard.
To see this at work, type cat and press ENTER. Unlike the earlier example, you do not get your shell
prompt back because cat is still running. Now type some stuff (it doesn't matter what). After you press
ENTER at the end of each line, cat repeats the line you typed. When you're sick of this, press CONTROL-
D on a line by itself to terminate the cat command and return to the shell prompt.
Note Do not confuse CONTROL-D and CONTROL-C. CONTROL-D on a line by itself stops the
current standard input entry (and often terminates a program). CONTROL-C terminates a
program regardless of its input or output.
You have now experienced standard input (stdin) and output (stdout), two important components of the
Unix shell environment. Standard input is a program's default input source. When you ran cat without any
arguments, it didn't give up because there were no arguments; instead, cat switched to standard input
instead of going after some files. Here, standard input was the stuff that came from your keyboard.
Standard output, on the other hand, is where a program's output goes by default. In this case, that location
is the terminal window running the shell. The best feature of standard input and output is that you can
easily send them to places other than their defaults, as described in Section 1.14.
1.3B asicHo Cw Loinmuxm Woarknsd: Wshat Every Super-User Should Know
by Brian Ward ISBN:1593270356
It's time to leNaor nSt sarocmh Per eostsh ©e r2 0U04n (i3x4 7c poamgesm) ands. Most of the following programs take multiple arguments, and
some have sTohi sm gaunidye odepstciorinbess a tnhed ifnonremr waotsr ktihnagst oafn a u Lninaubxr sidysgteedm lbisetginingn inwgo wuiltdh bthee pfiolei nstylsetsesm. Tanhdi sb oiso ta p rsoimcespsl iafinedd
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
list; you don't need to know all of the details just yet.
sharing printers with Samba.
1.3.1l s
Table of Contents
How Linux Works—What Every Super-User Should Know
ChTahpete lr s1 co-mThme aBnasdic lsists the contents of a directory. The default is the current directory. Use ls -l for a
Chdaepttaeirl e2d (-loDnegvi)c eliss, tDinisgk sa, nFdil elsyss te-mFs ,t oa nddi sthpela Kye rfnileel type information (for more on file types and the permissions
China pttheer 3left- cHoolwu mLinnu,x s Beoeo tSsection 1.17). Here is a sample long listing:
Chapter 4 -Essential System Files, Servers, and Utilities
Chtaopttear l5 3-6C1o6nfiguring Your Network
Ch-arpwte-r r6---rN-e-tw o1rk S ejruvisceesr users 3804 Apr 30 2000 abusive.c
Ch-arpwte-r r7---rIn-t-ro d1u ct iojnu tso eSrhe ll S c riuptssers 4165 May 26 1999 battery.zip
Ch-arpwte-r r8---rD-e-ve lo1p m ejnut sToeorls users 131219 Oct 26 2000 beav_1.40-13.tar.gz
Ch-arpwte-r r9---rC-o-m p1ili ng jSoufstwearre Fr o mu Ssoeurrcse C o de 6255 May 30 1999 country.c
Chdarpwtexr r1-0x-rM-axin ta2in i ngj uthsee Kre rn e l users 4096 Jul 17 20:00 cs335
Ch-arpwtexr r1-1x-rC-oxnf ig1u ri ngj uansde Mra n ip u lautisneg rPesr ip h er a l D e v7ic1e0s8 Feb 2 2001 dhry
Ch-arpwte-r r1-2--rP-ri-nt in1g juser users 11309 Oct 20 1999 dhry.c
Ch-arpwte-r r1-3--rB-a-ck u1ps juser users 56 Oct 6 1999 doit
Chdarpwtexr r1-4x-rS-hxar in6g F iljesu wsiethr S a m b ausers 4096 Feb 20 13:51 dw
Chdarpwtexr r1-5x-rN-extw o3rk Fijleu Tsraenrs fe r users 4096 May 2 2000 hough-stuff
Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
1.3.2c p
Appendix A-Command Classification
Bibliography
InIdne xthe first form shown below, cp copies the contents of file1 to file2. In the second form, it copies all
Lifsitl eosf Ftiog utrhees dir directory:
List of Tables
Licstp o ff iSlideeb1a rfsile2
cp file1 ... fileN dir
1.3.3m v
In the first form below, mv renames file1 to file2. In the second form, it moves all files to the dir
directory:
mv file1 file2
mv file1 ... fileN dir
1.3.4t ouch
The touch command creates a file. If the file already exists, touch does not change it, but it does update
the timestamp you see with the long listing that you get with the ls -l command.
touch file
1.3.5r m
To delete (remove) a file, use rm. After you remove a file, it's gone. Do not expect to be able to "undelete"
anything.
rm file
1.3.6e cho
How Linux Works: What Every Super-User Should Know
The echo cobmy mBraiannd W parridn ts its arguments to the standard output: ISBN:1593270356
No Starch Press © 2004 (347 pages)
This guide describes the inner workings of a Linux system beginning with the file system and boot process and
echo Hello there.
covering advanced topics such as networking, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
The echo command is very useful for finding expansions of shell wildcards and variables that you will
Table of Contents
encounter later in this chapter.
How Linux Works—What Every Super-User Should Know
Chapter 1 -The Basics
Chapter 2 -Devices, Disks, Filesystems, and the Kernel
Chapter 3 -How Linux Boots
Chapter 4 -Essential System Files, Servers, and Utilities
Chapter 5 -Configuring Your Network
Chapter 6 -Network Services
Chapter 7 -Introduction to Shell Scripts
Chapter 8 -Development Tools
Chapter 9 -Compiling Software From Source Code
Chapter 10 -Maintaining the Kernel
Chapter 11 -Configuring and Manipulating Peripheral Devices
Chapter 12 -Printing
Chapter 13 -Backups
Chapter 14 -Sharing Files with Samba
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Appendix A-Command Classification
Bibliography
Index
List of Figures
List of Tables
List of Sidebars
1.4U singHo wD Liirneuxc Wtoorrkys: WChoatm Evmerya Snupders-User Should Know
by Brian Ward ISBN:1593270356
Unix has a dNiroe Scttaorrcyh hPrieesrsa r©c 2h0y04 t h(3a47t psatgaerst)s at /, sometimes called the root. The directory separator is the
slash (/), notT hthise g buiadcek dselsacsrhib e(s\ t)h. eT ihnenerer waorrek isnegsv eorf aal Lsintaunx dsaysrtde msu bbedgiirnencintgo rwieitsh itnh et hfiele rsoyostte dmir aencdt obroyo,t spurocche sass and
/usr (you'll cloevaerrnin ga lal davbanocuetd t htoepmics isnu cShe acst inoent w2o.1rk)i.ng, firewalls, development tools, device management, shell scripts, and
sharing printers with Samba.
A directory specification is called a path, and one that starts at the root (such as /usr/lib) is a full or
Taabbles ooflu Cteon pteanthts. Similarly, a filename with a full path in front (such as /usr/lib/libc.a) is a full
Hopwa tLhinnuaxm Weo.rks—What Every Super-User Should Know
Chapter 1 -The Basics
ChTahpete pr 2ath- cDoemvicpeosn, eDnistk sid, eFinletsifyisetdem bsy, atwndo tdhoe tKse (r.ne.l) specifies the parent of your shell's current directory, and
Choanpete dr o3t (-.)H sopwe Lciinfuiexs B tohoets current directory. For example, if the current working directory of your shell is
Ch/aupsterr /4li-bE,s sthenet ipala Sthys .te.m/ Fbiilens, rSeefrevresrs t,o a n/du Ustrili/tibesin. A path beginning with .. or . is called a relative
Chpaaptthenr a5me-.Configuring Your Network
Chapter 6 -Network Services
ChTahpete fr o7llo-wIinntgro sdeuccttiioonn tso dSehsecll rSibcreip tthse essential directory commands.
Chapter 8 -Development Tools
Ch1a.p4ter. 19c -dCompiling Software From Source Code
Chapter 10 -Maintaining the Kernel
Chapter 11 -Configuring and Manipulating Peripheral Devices
The cd command changes the shell's current working directory to dir:
Chapter 12 -Printing
Chapter 13 -Backups
Chcadp dteir r14 -Sharing Files with Samba
Chapter 15 -Network File Transfer
Chapter 16 -User Environments
If you omit dir, the shell returns to your home directory.
Chapter 17 -Buying Hardware for Linux
Chapter 18 -Further Directions
Ap1p.e4nd.ix2 Am -Ckodmmirand Classification
Bibliography
InTdhexe mkdir command creates a new directory, dir:
List of Figures
List of Tables
mkdir dir
List of Sidebars
1.4.3r mdir
The rmdir command removes the directory dir:
rmdir dir
If dir isn't empty, this command fails. However, if you're impatient, you probably don't want to laboriously
delete all the files and subdirectories inside dir first. You can use rm -rf dir to delete a directory and
its contents, but be careful. This is one of the few commands that can do serious damage, especially if you
run it as the superuser. The -r option specifies recursive delete, and -f forces the delete operation. Don't
use the -rf flags with wildcards such as a star (*). Above all, always double-check your command.
1.4.4S hell Wildcards
The shell is capable of matching simple patterns with files in the current working directory. The simplest of
these is the star character (*), which means match any number of arbitrary characters. For example, the
following command prints a list of files in the current directory:
echo *
After matching files to wildcards, the shell substitutes the filenames for the wildcard in the command line
and then runs the revised command line. Here are some more wildcard examples: at* matches all files
starting with at;* at matches files that end with at; and *at* matches any files that contains at. If no
files match a wildcard, the shell does no substitution, and the command runs with literal characters such as
* (for example, try a command such as echo *dfkdsafh).