Ubuntu Server Administration

593 Pages·2008·11.8 MB·English

by  Michael Jang

Ubuntu® Server
Administration
MICHAEL JANG
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Ubuntu: humanity towards others.
ABOUT THE AUTHOR
Michael Jang (RHCE, UCP, LPIC-2, LCP, Linux+, MCP) is currently a full-time
writer who specializes in operating systems and networks. His experience with
computers goes back to the days of jumbled punch cards. He has written other
books on Linux certification, including RHCE Red Hat Certified Engineer Linux Study
Guide, Ubuntu Certified Professional Study Guide, Linux+ Certification Passport, and
Sair GNU/Linux Installation and Configuration Exam Cram. His other Linux books
include Linux Annoyances for Geeks, Linux Patch Management, and Mastering Fedora
Core Linux 5. He has also written or contributed to books on Microsoft operating
systems, including MCSE Guide to Microsoft Windows 98 and Mastering Windows XP
Professional, Second Edition.
About the Technical Editor
Elizabeth Zinkann is a logical Linux catalyst, a freelance technical editor, and
an independent computer consultant. She was a contributing editor and review
columnist for Sys Admin Magazine for 10 years. Some of her editing projects have
included RHCE Red Hat Certified Engineer Linux Study Guide, Linux+ Certification
Passport, Mastering Fedora Core Linux 5, Linux Patch Management, and Write Portable
Code. She owns an iBook that thinks it’s an “UbuntuBook” and is an avid digital
photographer. In a former life, she also programmed communications features,
including ISDN, at AT&T Network Systems.
CONTENTS
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix
▼ 1 The Ubuntu Community . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
A Short History of Ubuntu and Linux . . . . . . . . . . . . . . . . . . . . . . 2
Background on Unix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Linux Is Not Unix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
A Linux Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Linux and Open Source Licenses . . . . . . . . . . . . . . . . . . . . . 4
The Debian Project and Ubuntu . . . . . . . . . . . . . . . . . . . . . . 5
Ubuntu Just Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Hardy Heron Highlights . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
The Ubuntu Release Configuration . . . . . . . . . . . . . . . . . . . . . . . . 8
Past Releases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
The Ubuntu Development Cycle . . . . . . . . . . . . . . . . . . . . . 9
Support Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Desktop Environments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
The Ubuntu Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
v
vi
Ubuntu Server Administration
Participate in the Ubuntu Community . . . . . . . . . . . . . . . . . . . . . 12
Sponsored by Canonical . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Request a “Hard Copy” Release with ShipIt . . . . . . . . . . . . 13
The Ubuntu Launchpad . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Ubuntu Community Resources . . . . . . . . . . . . . . . . . . . . . . 16
Launchpad Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
The Ubuntu Wiki . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Ubuntu News and Security Notices . . . . . . . . . . . . . . . . . . . 20
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
▼ 2 Installing Ubuntu Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Acquire the Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Download the ISO File Online . . . . . . . . . . . . . . . . . . . . . . . 24
Download the ISO File from the Command Line . . . . . . . . . 26
Downloading the ISO File Cooperatively . . . . . . . . . . . . . . . 27
Write the ISO File to Disc . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Mount the ISO File on a Virtual Machine . . . . . . . . . . . . . . . 28
Mount the ISO File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Alternatives to Downloads . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Install from the CD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Stability or Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Hardware Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Linux Hardware Documentation . . . . . . . . . . . . . . . . . . . . . 31
The Ubuntu Server Installation Screen . . . . . . . . . . . . . . . . . 31
Install Ubuntu Server, Step by Step . . . . . . . . . . . . . . . . . . . . . . . . 34
Choose a Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Configure the Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Detect and Mount the CD-ROM . . . . . . . . . . . . . . . . . . . . . . 39
Load the Debconf Preconfiguration File . . . . . . . . . . . . . . . . 39
Load Installer Components from the CD . . . . . . . . . . . . . . . 39
Detect Network Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Configure the Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Continue Installation Remotely Using SSH . . . . . . . . . . . . . 42
Choose a Mirror of the Ubuntu Archive . . . . . . . . . . . . . . . . 44
Download Installer Components . . . . . . . . . . . . . . . . . . . . . 45
Configure the Clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Detect Disks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
Partition Disks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Configure MD Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Install the Base System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Set Up Users and Passwords . . . . . . . . . . . . . . . . . . . . . . . . 53
Configure the Package Manager . . . . . . . . . . . . . . . . . . . . . 54
vii
Contents
Select and Install Software . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Build LTSP Chroot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Install the GRUB Boot Loader on a Hard Disk . . . . . . . . . . . 58
Install the LILO Boot Loader on a Hard Disk . . . . . . . . . . . . 59
Continue Without Boot Loader . . . . . . . . . . . . . . . . . . . . . . 59
Finish the Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Change Debconf Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Check the CD-ROM(s) Integrity . . . . . . . . . . . . . . . . . . . . . 60
Save Debug Logs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Execute a Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Eject a CD from the Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Abort the Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Finish the Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Network Installations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Dynamic Host Configuration Protocol (DHCP) Services . . . 64
Trivial File Transfer Protocol . . . . . . . . . . . . . . . . . . . . . . . . 66
Configure a Network Installation . . . . . . . . . . . . . . . . . . . . . 66
PXE Booting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
▼ 3 Automated Installations with Kickstart . . . . . . . . . . . . . . . . . . . . . . . . . . 69
How to Kickstart an Installation . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Install the Kickstart Software . . . . . . . . . . . . . . . . . . . . . . . . 70
Use the Kickstart Configuration Tool . . . . . . . . . . . . . . . . . . 71
Customize the Kickstart File . . . . . . . . . . . . . . . . . . . . . . . . . 81
Boot an Installation with a Kickstart File . . . . . . . . . . . . . . . 84
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
▼ 4 The Boot Process and Rescue Mode . . . . . . . . . . . . . . . . . . . . . . . . . . 87
What Happens After Powering Up . . . . . . . . . . . . . . . . . . . . . . . . 88
The BIOS Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Making GRUB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
Kernels and Hardware Detection . . . . . . . . . . . . . . . . . . . . . 96
Upstart, RCs Scripts, and Services . . . . . . . . . . . . . . . . . . . . 96
Rescue Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Recovery and Single-User Mode . . . . . . . . . . . . . . . . . . . . . 100
Using the GRUB Command Line . . . . . . . . . . . . . . . . . . . . . 102
The Installation CD Rescue Mode . . . . . . . . . . . . . . . . . . . . 104
Using a LiveCD/DVD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
viii
Ubuntu Server Administration
▼ 5 Filesystem Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
Make the Filesystem Work for You . . . . . . . . . . . . . . . . . . . . . . . . 110
The Filesystem Hierarchy Standard . . . . . . . . . . . . . . . . . . . 110
Partition Device Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
Create Partitions with fdisk . . . . . . . . . . . . . . . . . . . . . . . . . 113
The parted Utility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
Format New Filesystems . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Manage Filesystems in /etc/fstab . . . . . . . . . . . . . . . . . . . . 124
How to Make RAID Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
RAID Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Create RAID Partitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
Format and Configure a RAID Array . . . . . . . . . . . . . . . . . . 130
Use an Active RAID Array . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Maintaining RAID Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . 132
Make RAID Work in /etc/fstab . . . . . . . . . . . . . . . . . . . . . . 132
Logical Volumes Promote Flexibility . . . . . . . . . . . . . . . . . . . . . . . 133
Logical Volume Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
Create Physical Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Creating a Volume Group . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
Creating a Logical Volume . . . . . . . . . . . . . . . . . . . . . . . . . . 136
Activate Logical Volumes . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Configure Logical Volumes in /etc/fstab . . . . . . . . . . . . . . . 139
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
▼ 6 Command Line Tools and Shell Management . . . . . . . . . . . . . . . . . . . . 141
Command Line Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Interactivity and Command Completion . . . . . . . . . . . . . . . 142
Navigate Around Directories . . . . . . . . . . . . . . . . . . . . . . . . 144
File Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
Quotes and Backslashes . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
Aliases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
Wildcards in a Glob . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
File Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Command Combinations and Data Streams . . . . . . . . . . . . 153
Set the Default Linux Text Editor . . . . . . . . . . . . . . . . . . . . . 154
Optimize the Shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Profiles in Bash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
A Minor in Scripts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Variables and More . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
Manage Permissions, Octal and Super . . . . . . . . . . . . . . . . . . . . . 158
Basic File Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Commands to Modify Permissions and Ownership . . . . . . 159
ix
Contents
Special File Permissions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
Access Control Lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
▼ 7 Basic Administrative Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Create a Secure Shell Server . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
Configuring the SSH Server . . . . . . . . . . . . . . . . . . . . . . . . . 168
Passphrases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
A Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Client Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Telnet if You Must . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Schedule Important Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Standard cron Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
User cron Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
Configure at Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Job Scheduling Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Customize Services and Runlevels . . . . . . . . . . . . . . . . . . . . . . . . 181
Script Actions in Different Runlevels . . . . . . . . . . . . . . . . . . 181
Manage when a Service Starts and Stops . . . . . . . . . . . . . . . 182
Manage Those Log Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
General Log Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . 185
General Log Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Service-Specific Log Files . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Log Rotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
▼ 8 Manage Updates and Local Repositories . . . . . . . . . . . . . . . . . . . . . . . 191
The Basics of dpkg and apt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
A Background in dpkg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Ubuntu Repository Organization . . . . . . . . . . . . . . . . . . . . . 194
Repository Source Management . . . . . . . . . . . . . . . . . . . . . . 195
Find the Right Mirror . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
Fundamental apt Commands . . . . . . . . . . . . . . . . . . . . . . . . 198
More apt Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Update Management Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 202
The Task Selector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
Keep the Server Up-to-Date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Security Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Kernel Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
Application Updates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210