LINUX: Rute User’s Tutorial and Exposition Paul Sheer August 14, 2001 Pages up to and including this page are not included by Prentice Hall. 2 “The reason we don’t sell billions and billions of Guides,” continued Harl, after wiping his mouth, “is the expense. What we do is we sell one Guide billions and billions of times. We exploit the multidimensional nature of the Universe to cut down on manufacturing costs. And we don’t sell to penniless hitchhikers. What a stupid notion that was! Find the one section of the market that, more or less by definition, doesn’t have any money, and try to sell to it. No. We sell to the affluent business traveler and his vacationing wife in a billion, billion different futures. This is the most radical, dynamic and thrusting business venture in the entire multidimensional infinity of space-time-probability ever.” Ford was completely at a loss for what to do next. “Look,” he said in a stern voice. But he wasn’t certain how far saying things like “Look” in a stern voice was necessarily going to get him, and time was not on his side. What the hell, he thought, you’re only young once, and threw himself out of the window. That would at least keep the element of surprise on his side. In a spirit of scientific inquiry he hurled himself out of the window again. Douglas Adams Mostly Harmless Strangely, the thing that least intrigued me was how they’d managed to get it all done. I suppose I sort of knew. If I’d learned one thing from traveling, it was that the way to get things done was to go ahead and do them. Don’t talk about going to Borneo. Book a ticket, get a visa, pack a bag, and it just happens. Alex Garland The Beach vi Chapter Summary 1 Introduction 1 2 Computing Sub-basics 5 3 PC Hardware 15 4 Basic Commands 25 5 Regular Expressions 49 6 Editing Text Files 53 7 Shell Scripting 61 8 Streams and sed — The Stream Editor 73 9 Processes, Environment Variables 81 10 Mail 97 11 User Accounts and Ownerships 101 12 Using Internet Services 111 13 L INUX Resources 117 14 Permission and Modification Times 123 15 Symbolic and Hard Links 127 16 Pre-installed Documentation 131 17 Overview of the U NIX Directory Layout 135 18 U NIX Devices 141 19 Partitions, File Systems, Formatting, Mounting 153 20 Advanced Shell Scripting 171 21 System Services and lpd 193 22 Trivial Introduction to C 207 23 Shared Libraries 233 24 Source and Binary Packages 237 25 Introduction to IP 247 26 TCP and UDP 263 vii Chapter Summary 27 DNS and Name Resolution 273 28 Network File System, NFS 285 29 Services Running Under inetd 291 30 exim and sendmail 299 31 lilo, initrd, and Booting 317 32 init, ?getty, and U NIX Run Levels 325 33 Sending Faxes 333 34 uucp and uux 337 35 The LINUX File System Standard 347 36 httpd — Apache Web Server 389 37 crond and atd 409 38 postgres SQL Server 413 39 smbd — Samba NT Server 425 40 named — Domain Name Server 437 41 Point-to-Point Protocol — Dialup Networking 453 42 The L INUX Kernel Source, Modules, and Hardware Support 463 43 The X Window System 485 44 UNIX Security 511 A Lecture Schedule 525 B LPI Certification Cross-Reference 531 C RHCE Certification Cross-Reference 543 DL INUX Advocacy FAQ 551 E The GNU General Public License Version 2 573 Index 581 viii Contents Acknowledgments xxxi 1 Introduction 1 1.1 What This Book Covers 1 1.2 Read This Next. . . 1 1.3 What Do I Need to Get Started? 1 1.4 MoreAboutThisBook 2 1.5 I Get Frustrated with U NIX Documentation That I Don’t Understand . . 2 1.6 LPI and RHCE Requirements 2 1.7 Not RedHat: RedHat-like 3 1.8 Updates and Errata 3 2 Computing Sub-basics 5 2.1 Binary, Octal, Decimal, and Hexadecimal 5 2.2 Files 7 2.3 Commands 8 2.4 Login and Password Change 9 2.5 Listing Files 10 2.6 Command-Line Editing Keys 10 2.7 ConsoleKeys 11 2.8 Creating Files 12 2.9 Allowable Characters for File Names 12 2.10 Directories 12 3 PC Hardware 15 3.1 Motherboard 15 3.2 Master/Slave IDE 19 ix Contents 3.3 CMOS 20 3.4 Serial Devices 20 3.5 Modems 23 4 Basic Commands 25 4.1 The ls Command, Hidden Files, Command-Line Options 25 4.2 Error Messages 26 4.3 Wildcards, Names, Extensions, and glob Expressions 29 4.3.1 File naming 29 4.3.2 Glob expressions 32 4.4 Usage Summaries and the Copy Command 33 4.5 Directory Manipulation 34 4.6 Relative vs. Absolute Pathnames . 34 4.7 System Manual Pages 35 4.8 System info Pages 36 4.9 Some Basic Commands 36 4.10 The mc File Manager 40 4.11 Multimedia Commands for Fun 40 4.12 Terminating Commands 41 4.13 Compressed Files 41 4.14 Searching for Files 42 4.15 Searching Within Files 43 4.16 Copying to MS-DOS and Windows Formatted Floppy Disks 44 4.17 Archives and Backups 45 4.18 The PATH Where Commands Are Searched For 46 4.19 The Option 47 5 Regular Expressions 49 5.1 Overview 49 5.2 The fgrep Command 51 5.3 Regular Expression \{ \} Notation 51 5.4 + ? \< \> ( ) | Notation 52 5.5 Regular Expression Subexpressions 52 x Contents 6 Editing Text Files 53 6.1 vi 53 6.2 Syntax Highlighting 57 6.3 Editors 57 6.3.1 Cooledit 58 6.3.2 vi and vim 58 6.3.3 Emacs 59 6.3.4 Other editors 59 7 Shell Scripting 61 7.1 Introduction 61 7.2 Looping: the while and until Statements 62 7.3 Looping: the for Statement 63 7.4 breaking Out of Loops and continueing 65 7.5 Looping Over Glob Expressions 66 7.6 The case Statement 66 7.7 Using Functions: the function Keyword 67 7.8 Properly Processing Command-Line Args: shift 68 7.9 More on Command-Line Arguments: $@ and $0 70 7.10 Single Forward Quote Notation 70 7.11 Double-Quote Notation 70 7.12 Backward-Quote Substitution 71 8 Streams and sed — The Stream Editor 73 8.1 Introduction 73 8.2 Tutorial 74 8.3 Piping Using | Notation 74 8.4 A Complex Piping Example 75 8.5 Redirecting Streams with >& 75 8.6 Using sed to Edit Streams 77 8.7 Regular Expression Subexpressions 77 8.8 Inserting and Deleting Lines 79 9 Processes, Environment Variables 81 9.1 Introduction 81 9.2 ps — List Running Processes 82 9.3 Controlling Jobs 82 xi Contents 9.4 Creating Background Processes 83 9.5 killing a Process, Sending Signals 84 9.6 List of Common Signals 86 9.7 Niceness of Processes, Scheduling Priority 87 9.8 Process CPU/Memory Consumption, top 88 9.9 Environments of Processes 90 10 Mail 97 10.1 Sending and Reading Mail 99 10.2 The SMTP Protocol — Sending Mail Raw to Port 25 99 11 User Accounts and Ownerships 101 11.1 File Ownerships 101 11.2 The Password File /etc/passwd 102 11.3 Shadow Password File: /etc/shadow 103 11.4 The groups Command and /etc/group 104 11.5 Manually Creating a User Account 105 11.6 Automatically: useradd and groupadd 106 11.7 User Logins 106 11.7.1 The login command 106 11.7.2 The set user, su command 107 11.7.3 The who, w, and users commands to see who is logged in 108 11.7.4 The id command and effective UID 109 11.7.5 User limits 109 12 Using Internet Services 111 12.1 ssh, not telnet or rlogin 111 12.2 rcp and scp 112 12.3 rsh 112 12.4 FTP 113 12.5 finger 114 12.6 Sending Files by Email 114 12.6.1 uuencode and uudecode 114 12.6.2 MIME encapsulation 115 xii Contents 13 LINUX Resources 117 13.1 FTP Sites and the sunsite Mirror 117 13.2 HTTP — Web Sites 118 13.3 SourceForge 119 13.4 Mailing Lists 119 13.4.1 Majordomo and Listserv 119 13.4.2 *-request 120 13.5 Newsgroups 120 13.6 RFCs 121 14 Permission and Modification Times 123 14.1 The chmod Command 123 14.2 The umask Command 125 14.3 Modification Times: stat 126 15 Symbolic and Hard Links 127 15.1 Soft Links 127 15.2 Hard Links 129 16 Pre-installed Documentation 131 17 Overview of the U NIX Directory Layout 135 17.1 Packages 135 17.2 U NIX Directory Superstructure . . . 136 17.3 L INUX on a Single Floppy Disk 138 18 U NIX Devices 141 18.1 Device Files 141 18.2 Block and Character Devices 142 18.3 Major and Minor Device Numbers 143 18.4 Common Device Names 143 18.5 dd, tar, and Tricks with Block Devices 147 18.5.1 Creating boot disks from boot images 147 18.5.2 Erasing disks 147 18.5.3 Identifying data on raw disks 148 18.5.4 Duplicating a disk 148 18.5.5 Backing up to floppies 149 xiii Contents 18.5.6 Tape backups 149 18.5.7 Hiding program output, creating blocks of zeros 149 18.6 Creating Devices with mknod and /dev/MAKEDEV 150 19 Partitions, File Systems, Formatting, Mounting 153 19.1 The Physical Disk Structure 153 19.1.1 Cylinders, heads, and sectors 153 19.1.2 Large Block Addressing 154 19.1.3 Extended partitions 154 19.2 Partitioning a New Disk 155 19.3 Formatting Devices 160 19.3.1 File systems 160 19.3.2 mke2fs 160 19.3.3 Formatting floppies and removable drives 161 19.3.4 Creating MS-DOS floppies 162 19.3.5 mkswap, swapon, and swapoff 162 19.4 Device Mounting 163 19.4.1 Mounting CD-ROMs 163 19.4.2 Mounting floppy disks 164 19.4.3 Mounting Windows and NT partitions 164 19.5 File System Repair: fsck 165 19.6 File System Errors on Boot 165 19.7 Automatic Mounts: fstab 166 19.8 Manually Mounting /proc 167 19.9 RAM and Loopback Devices 167 19.9.1 Formatting a floppy inside a file 167 19.9.2 CD-ROM files 168 19.10 Remounting 168 19.11 Disk sync 169 20 Advanced Shell Scripting 171 20.1 Lists of Commands 171 20.2 Special Parameters: $?, $*, 172 20.3 Expansion 173 20.4 Built-in Commands 175 20.5 Trapping Signals — the trap Command 176 xiv Contents 20.6 Internal Settings — the set Command 177 20.7 Useful Scripts and Commands 178 20.7.1 chroot 178 20.7.2 if conditionals 179 20.7.3 patching and diffing 179 20.7.4 Internet connectivity test 180 20.7.5 Recursive grep (search) 180 20.7.6 Recursive search and replace 181 20.7.7 cut and awk — manipulating text file fields 182 20.7.8 Calculations with bc 183 20.7.9 Conversion of graphics formats of many files 183 20.7.10 Securely erasing files 184 20.7.11 Persistent background processes 184 20.7.12 Processing the process list 185 20.8 Shell Initialization 186 20.8.1 Customizing the PATH and LD LIBRARY PATH 187 20.9 File Locking 187 20.9.1 Locking a mailbox file 188 20.9.2 Locking over NFS 190 20.9.3 Directory versus file locking 190 20.9.4 Locking inside C programs 191 21 System Services and lpd 193 21.1 Using lpr 193 21.2 Downloading and Installing 194 21.3 LPRng vs. Legacy lpr-0.nn 195 21.4 Package Elements 195 21.4.1 Documentation files 195 21.4.2 Web pages, mailing lists, and download points 195 21.4.3 User programs 196 21.4.4 Daemon and administrator programs 196 21.4.5 Configuration files 196 21.4.6 Service initialization files 196 21.4.7 Spool files 197 21.4.8 Log files 198 21.4.9 Log file rotation 198 xv Contents 21.4.10 Environment variables 199 21.5 The printcap File in Detail 199 21.6 PostScript and the Print Filter 200 21.7 Access Control 202 21.8 Printing Troubleshooting 203 21.9 Useful Programs 204 21.9.1 printtool 204 21.9.2 apsfilter 204 21.9.3 mpage 204 21.9.4 psutils 204 21.10 Printing to Things Besides Printers 205 22 Trivial Introduction to C 207 22.1 C Fundamentals 208 22.1.1 The simplest C program 208 22.1.2 Variables and types 209 22.1.3 Functions 210 22.1.4 for, while, if, and switch statements 211 22.1.5 Strings, arrays, and memory allocation 213 22.1.6 String operations 215 22.1.7 File operations 217 22.1.8 Reading command-line arguments inside C programs 218 22.1.9 A more complicated example 218 22.1.10 #include statements and prototypes 220 22.1.11 C comments 221 22.1.12 #define and #if — C macros 222 22.2 Debugging with gdb and strace 223 22.2.1 gdb 223 22.2.2 Examining core files 227 22.2.3 strace 227 22.3 C Libraries 227 22.4 C Projects — Makefiles 230 22.4.1 Completing our example Makefile 231 22.4.2 Putting it all together 231 xvi Contents 23 Shared Libraries 233 23.1 Creating DLL .so Files 233 23.2 DLL Versioning 234 23.3 Installing DLL .so Files 235 24 Source and Binary Packages 237 24.1 Building GNU Source Packages 237 24.2 RedHat and Debian Binary Packages 240 24.2.1 Package versioning 240 24.2.2 Installing, upgrading, and deleting 240 24.2.3 Dependencies 241 24.2.4 Package queries 241 24.2.5 File lists and file queries 242 24.2.6 Package verification 243 24.2.7 Special queries 244 24.2.8 dpkg/apt versus rpm 245 24.3 Source Packages 246 25 Introduction to IP 247 25.1 Internet Communication 247 25.2 Special IP Addresses 249 25.3 Network Masks and Addresses 250 25.4 Computers on a LAN 250 25.5 Configuring Interfaces 251 25.6 Configuring Routing 252 25.7 Configuring Startup Scripts 254 25.7.1 RedHat networking scripts 254 25.7.2 Debian networking scripts 255 25.8 Complex Routing — a Many-Hop Example 256 25.9 Interface Aliasing — Many IPs on One Physical Card 259 25.10 Diagnostic Utilities 260 25.10.1 ping 260 25.10.2 traceroute 261 25.10.3 tcpdump 261 xvii Contents 26 TCP and UDP 263 26.1 The TCP Header 264 26.2 A Sample TCP Session 265 26.3 User Datagram Protocol (UDP) 268 26.4 /etc/services File 269 26.5 Encrypting and Forwarding TCP 270 27 DNS and Name Resolution 273 27.1 Top-Level Domains (TLDs) 273 27.2 Resolving DNS Names to IP Addresses 274 27.2.1 The Internet DNS infrastructure 275 27.2.2 The name resolution process 276 27.3 Configuring Your Local Machine 277 27.4 Reverse Lookups 281 27.5 Authoritative foraDomain 281 27.6 The host, ping, and whois Command 281 27.7 The nslookup Command 282 27.7.1 NS, MX, PTR, A and CNAME records 283 27.8 The dig Command 284 28 Network File System, NFS 285 28.1 Software 285 28.2 Configuration Example 286 28.3 Access Permissions 288 28.4 Security 289 28.5 Kernel NFS 289 29 Services Running Under inetd 291 29.1 The inetd Package . 291 29.2 Invoking Services with /etc/inetd.conf 291 29.2.1 Invoking a standalone service 292 29.2.2 Invoking an inetd service 292 29.2.3 Invoking an inetd “TCP wrapper” service 293 29.2.4 Distribution conventions 294 29.3 Various Service Explanations 294 29.4 The xinetd Alternative 295 29.5 Configuration Files 295 xviii Contents 29.5.1 Limiting access 296 29.6 Security 297 30 exim and sendmail 299 30.1 Introduction 299 30.1.1 How mail works 299 30.1.2 Configuring a POP/IMAP server 301 30.1.3 Why exim? 301 30.2 exim Package Contents 301 30.3 exim Configuration File 302 30.3.1 Global settings 303 30.3.2 Transports 304 30.3.3 Directors 305 30.3.4 Routers 306 30.4 Full-blown Mail server 306 30.5 Shell Commands for exim Administration 308 30.6 The Queue 309 30.7 /etc/aliases for Equivalent Addresses 310 30.8 Real-Time Blocking List — Combating Spam 311 30.8.1 What is spam? 311 30.8.2 Basic spam prevention 312 30.8.3 Real-time blocking list 313 30.8.4 Mail administrator and user responsibilities 313 30.9 Sendmail 314 31 lilo, initrd, and Booting 317 31.1 Usage 317 31.2 Theory 318 31.2.1 Kernel boot sequence 318 31.2.2 Master boot record 318 31.2.3 Booting partitions 318 31.2.4 Limitations 319 31.3 lilo.conf and the lilo Command 319 31.4 Creating Boot Floppy Disks 321 31.5 SCSI Installation Complications and initrd 322 31.6 Creating an initrd Image 322 31.7 Modifying lilo.conf for initrd 324 31.8 Using mkinitrd 324 xix Contents 32 init, ?getty, and UNIX Run Levels 325 32.1 init — the First Process 325 32.2 /etc/inittab 326 32.2.1 Minimal configuration 326 32.2.2 Rereading inittab 328 32.2.3 The respawning too fast error 328 32.3 Useful Run Levels 328 32.4 getty Invocation 329 32.5 Bootup Summary 329 32.6 Incoming Faxes and Modem Logins 330 32.6.1 mgetty with character terminals 330 32.6.2 mgetty log files 330 32.6.3 mgetty with modems 330 32.6.4 mgetty receiving faxes 331 33 Sending Faxes 333 33.1 Fax Through Printing 333 33.2 Setgid Wrapper Binary 335 34 uucp and uux 337 34.1 Command-Line Operation 338 34.2 Configuration 338 34.3 Modem Dial 341 34.4 tty/UUCP Lock Files 342 34.5 Debugging uucp 343 34.6 Using uux with exim 343 34.7 Scheduling Dialouts 346 35 The L INUX File System Standard 347 35.1 Introduction 349 35.1.1 Purpose 349 35.1.2 Conventions 349 35.2 The Filesystem 349 35.3 The Root Filesystem 351 35.3.1 Purpose 351 35.3.2 Requirements 352 35.3.3 Specific Options 352 xx Contents 35.3.4 /bin : Essential user command binaries (for use by all users) . . 353 35.3.5 /boot : Static files of the boot loader 354 35.3.6 /dev : Device files 355 35.3.7 /etc : Host-specific system configuration 355 35.3.8 /home : User home directories (optional) 358 35.3.9 /lib : Essential shared libraries and kernel modules 358 35.3.10 /lib<qual> : Alternate format essential shared libraries (optional)359 35.3.11 /mnt : Mount point for a temporarily mounted filesystem 359 35.3.12 /opt : Add-on application software packages 360 35.3.13 /root : Home directory for the root user (optional) 361 35.3.14 /sbin : System binaries 361 35.3.15 /tmp : Temporary files 362 35.4 The /usr Hierarchy 362 35.4.1 Purpose 362 35.4.2 Requirements 363 35.4.3 Specific Options 363 35.4.4 /usr/X11R6 : X Window System, Version 11 Release 6 (optional) 363 35.4.5 /usr/bin : Most user commands 364 35.4.6 /usr/include : Directory for standard include files. 365 35.4.7 /usr/lib : Libraries for programming and packages 365 35.4.8 /usr/lib<qual> : Alternate format libraries (optional) 366 35.4.9 /usr/local : Local hierarchy 366 35.4.10 /usr/sbin : Non-essential standard system binaries 367 35.4.11 /usr/share : Architecture-independent data 367 35.4.12 /usr/src : Source code (optional) 373 35.5 The /var Hierarchy 373 35.5.1 Purpose 373 35.5.2 Requirements 373 35.5.3 Specific Options 374 35.5.4 /var/account : Process accounting logs (optional) 374 35.5.5 /var/cache : Application cache data 374 35.5.6 /var/crash : System crash dumps (optional) 376 35.5.7 /var/games : Variable game data (optional) 376 35.5.8 /var/lib : Variable state information 377 35.5.9 /var/lock : Lock files 379 35.5.10 /var/log : Log files and directories 379 xxi Contents 35.5.11 /var/mail : User mailbox files (optional) 379 35.5.12 /var/opt : Variable data for /opt 380 35.5.13 /var/run : Run-time variable data 380 35.5.14 /var/spool : Application spool data 381 35.5.15 /var/tmp : Temporary files preserved between system reboots . 382 35.5.16 /var/yp : Network Information Service (NIS) database files (op- tional) 382 35.6 Operating System Specific Annex 382 35.6.1 Linux 382 35.7 Appendix 386 35.7.1 The FHS mailing list 386 35.7.2 Background of the FHS 386 35.7.3 General Guidelines 386 35.7.4 Scope 386 35.7.5 Acknowledgments 387 35.7.6 Contributors 387 36 httpd — Apache Web Server 389 36.1 Web Server Basics 389 36.2 Installing and Configuring Apache 393 36.2.1 Sample httpd.conf 393 36.2.2 Common directives 394 36.2.3 User HTML directories 398 36.2.4 Aliasing 398 36.2.5 Fancy indexes 399 36.2.6 Encoding and language negotiation 399 36.2.7 Server-side includes — SSI 400 36.2.8 CGI — Common Gateway Interface 401 36.2.9 Forms and CGI 403 36.2.10 Setuid CGIs 405 36.2.11 Apache modules and PHP 406 36.2.12 Virtual hosts 407 37 crond and atd 409 37.1 /etc/crontab Configuration File 409 37.2 The at Command 411 37.3 Other cron Packages 412 xxii [...]... convenient Commands under the GNU free software license are superior in this way: they have a greater number of options than traditional U NIX commands and are therefore more flexible , for example, ls -a -l, ls -l -a, or ls -al —any of these will list all files in long format & - commands take the additional arguments -h and help You can All GNU type a command with just this on the command-line and get a... > You will see that the command cat writes the contents of a file to the screen, allowing you to view your letter It should match exactly what you typed in Your command-line keeps a history of all the commands you have typed in Ctrlp and Ctrl-n will cycle through previous commands entered New users seem to gain tremendous satisfaction from typing in lengthy commands over and over Never type in anything... sequences begin with the letters AT and are called ATtention commands AT commands are sent by your computer to configure your modem for the current telephone line conditions, intended function, and serial port capability—for example, there are commands to: enable automatic answering on ring; set the flow control method; dial a number; and hang up The sequence of commands used to configure the modem is... issue these commands is discussed in Section 32.6.3, 34.3, and 41.1 and will become relevant when you want to dial your Internet service provider (ISP) Because each modem brand supports a slightly different set of modem commands, it is worthwhile familiarizing yourself with your modem manual Most modern modems now support the Hayes command set—a generic set of the most useful modem commands However,... you type the command ls to list the contents of a directory To see a hidden file you must use the command ls -a The -a option means to list all files as well as hidden files Another variant is ls -l, which lists the contents in long format The - is used in this way to indicate variations on a command These are called command-line options or command-line arguments, and most U NIX commands can take a number... yet Most U NIX commands do not give any kind of message unless something went wrong (the passwd command above was an exception) If there were files, you would see their names listed rather blandly in columns with no indication of what they are for 2.6 Command-Line Editing Keys The following keys are useful for editing the command-line Note that U NIX has had a , and other keys may long and twisted evolution... X or Y; and *[a-d]id matches all files ending with aid, bid, cid or did; and *.{cpp,c,cxx} matches all files ending in cpp, c or cxx This way of specifying a file name is called a glob expression Glob expressions are used in many different contexts, as you will see later 32 4 Basic Commands 4.4 Usage Summaries and the Copy Command 4.5 Directory Manipulation 4 Basic Commands 4.4 Usage Summaries and the... terminal date Prints out the current date and time (The command time, though, does something entirely different.) You should now use the man command to look up the manual pages for all the commands that you have learned Type man cp, man mv, man rm, man mkdir, man rmdir, man passwd, man cd, man pwd, and of course man man Much of the df Stands for disk free and tells you how much free space is left on... for source code, file formats, and file systems.- Go to the end of a file ssss Search backward through a file for the text ssss ¤ ✞ LESS=-Q export LESS ✝ ✆ and then logging out and logging in again But this is an aside that will make more sense later.) 38 4 Basic Commands 4.9 Some Basic Commands - at the & 4.10 The mc File Manager 4 Basic Commands lynx Opens a URL URL stands for Uniform Resource Locator—a... Error Messages All of U NIX is case sensitive A command with even a single letter’s capitalization altered is considered to be a completely different command The same goes for files, directories, configuration file formats, and the syntax of all native programming languages 4.1 The ls Command, Hidden Files, Command-Line Options In addition to directories and ordinary text files, there are other types of files, . LINUX: Rute User’s Tutorial and Exposition Paul Sheer August 14, 2001 Pages up to and including this page are not included by Prentice Hall. 2 “The reason we don’t sell billions and billions. inetd 291 30 exim and sendmail 299 31 lilo, initrd, and Booting 317 32 init, ?getty, and U NIX Run Levels 325 33 Sending Faxes 333 34 uucp and uux 337 35 The LINUX File System Standard 347 36 httpd. Understand . . 2 1.6 LPI and RHCE Requirements 2 1.7 Not RedHat: RedHat-like 3 1.8 Updates and Errata 3 2 Computing Sub-basics 5 2.1 Binary, Octal, Decimal, and Hexadecimal 5 2.2 Files 7 2.3 Commands