Linux Home Networking
Grief Relief For The Home And Small Office
Peter Harrison
www.linuxhomenetworking.com
May 3, 2003Copyright
© Peter Harrison 2002-2003, All rights reserved. ISBN 0-9729355-0-9
Unless otherwise stated, the material published within this document is copyright of the author, Peter Harrison. No part of of this document, including page design, interior design, cover design and icons may be reproduced or transmitted in any form, by any means, (electronic, photocopying, recording, or otherwise) without the prior consent of the publisher/author.
Disclaimer – The Website and Manual
While every effort will be made to ensure that the information contained within the is website and manual is accurate and up to date, the author makes no warranty, representation or undertaking whether
expressed or implied, nor does it assume any legal liability, whether direct or indirect, or responsibility for the accuracy, completeness, or usefulness of any information.
Disclaimer - Other sites
Hypertext links to sites outside this website are provided as a convenience to users and should not necessarily be construed as an endorsement. Although every care is taken to provide links to suitable material from this site, the nature of the Internet prevents the author from guaranteeing the suitability or accuracy of any of the material that this site may be linked to. Consequently, the author can accept no responsibility for unsuitable or inaccurate material that may be encountered and accepts no liability whether direct or indirect for any loss or damage a person suffers because that person had directly or indirectly relied on any information stored in the hypertext links.
Further, the author is not and can not be responsible for the accuracy or legitimacy of information found elsewhere on the Internet and there is therefore no guarantee or warranty that any of the sites listed will be available at any particular time. The author does not guarantee or warrant any services that might be announced - use at your own risk.
The author makes no warranty, representation or undertaking whether expressed or implied nor does it assume any legal responsibility for the accuracy, completeness of usefulness of the information in the hypertext links.
Introduction
D
uring the “.com” gold rush, I decided to set up a small website dedicated to Caribbean art. The company I used made it really easy, all I had to do was copy my files to the web server using the username and password they provided.One day at work I overheard some friends saying that they were hosting their websites from home using their DSL line. I suddenly decided to do the same and moved www.simiya.com literally “in-house”. Of course, it wasn’t as easy as they had made it seem. I generally found a majority of Linux resources on the web to be either too detailed or too vague or just inaccurate. There were many excellent articles on specific topics, but they were usually part of a general interest publication, and information on related topics on the site was sometimes hard to find.
There just wasn’t a site out there for intermediate Linux home users who wanted to get their feet wet in web hosting, nor did there seem to be any similar sites targeting the poor I.T. people who are told to “get Linux working by tomorrow”.
After a few months I decided that no one should have to repeat my pain and I added some technical pages to the site. Soon, www.linuxhomenetworking.com was born.
This manual assumes you have a few weeks of Linux experience and understand the basics, such as file management and the use of text editors such as “vi”. This approach was taken in order to keep its focus on the intermediate user who requires a compact guide.
It’s ironic to know that in the beginning I learned from the web as I just wasn’t prepared to buy too many Linux books, now I’ve created this manual because web users were constantly asking me to write one. If you like this manual, feel free to visit the site and let me know. Without your encouragement it wouldn’t have happened at all.
i
Table Of Contents
Chapter 1 ... 15
Adding Linux Users ... 15
Who Is The Super User? ...15
How To Add Users...15
How To Change Passwords...16
How To Delete Users ...17
How To Tell The Groups To Which A User Belongs ...17
Chapter 2 ... 19
Using Sudo... 19
What is sudo?...19
Download and Install The sudo Package ...20
The visudo Command ...20
The /etc/sudoers File ...20
General Guidelines ...20
Simple Examples ...20
How To Use sudo ...21
Using syslog To Track All sudo Commands ...21
Chapter 3 ... 23
Installing RPM Software ... 23
Where To Get Commonly Used RPMs...23
RPMs On Your Installation CDs ...24
RPMs Downloaded From Redhat...24
RPMs Downloaded From Speakeasy...24
How to Easily Access CD RPMs With Automount ...24
Downloading RPMS To Your Linux Box...25
Getting RPMs Using Web Based FTP...26
RedHat...26
Speakeasy ...26
Getting RPMs Using Command Line Anonymous FTP ...26
How To Install The RPMs ...29
Using Downloaded Files ...29
Using CDROMs...29
How to Install Source RPMs...29
Newer Linux Versions ...30
Older Linux Versions ...31
How To List Installed RPMs ...31
How Uninstall RPMs...32
RedHat Up2date ...32
Some Necessary Facts About up2date ...34
The RedHat Boot Sequence ...37
Determining The Default Boot runlevel...38
Get A GUI Console ...38
Get A Basic Text Terminal Without Exiting The GUI ...39
Using A GUI Terminal Window ...39
Using Virtual Terminals ...39
System Shutdown And Rebooting...39
Halt / Shutdown The System...39
Reboot The System ...39
How To Set Which Programs Run At Each runlevel ...40
Chkconfig Examples...40
Use Chkconfig To Get A Listing Of Sendmail's Current Startup Options ...40
Switch Off Sendmail Starting Up In Levels 3 and 5 ...40
Doublecheck That Sendmail Will Not Startup...40
Turn it back on again ...41
Final Tips On chkconfig...41
Chapter 5 ... 43
Why Host Your Own Site?... 43
Network Diagram ...43
Alternatives To Home Web Hosting ...44
Factors To Consider Before Hosting Yourself ...44
Home Based Websites...44
Pros ...44
Cons...44
Small Office Based Websites...45
Pros ...45
Cons...45
How To Migrate From An External Provider ...46
Chapter 6 ... 47
Introduction To Networking... 47
What Is TCP/IP? ...48
What is TCP?...48
What is UDP? ...48
What are TCP / UDP Ports?...48
What is a TTL? ...49
What is ICMP?...49
What Do IP Addresses Look Like?...49
Private IP Addresses ...50
What Is Localhost? ...50
What Is A Subnet Mask? ...50
How Many Addresses Do I Get With My Mask? ...51
What’s The Range Of Addresses On My Network? ...51
Manual Calculation ...51
Calculation Using A Script ...52
What Is Duplex?...52 What Is A Hub? ...52 What Is A Switch?...53 What Is A LAN?...53 What Is A Router?...53 What Is A Gateway?...54 What Is A Route?...54
What Is A Default Gateway? ...54
Table Of Contents iii
What Is A MAC Address? ...55
What Is ARP? ...55
What Is A Firewall?...56
What Is NAT? ...56
What Is Port Forwarding With NAT?...56
What Is DHCP? ...57
What Is DNS?...57
How Can I Check The IP Address For A Domain?...58
How Do I Get My Own DNS Domain Name? ...59
Static or Dynamic DNS? ...59
What is FTP?...59
Regular FTP...59
Anonymous FTP ...59
Where is Linux Help? ...60
Finding General Information On A Command ...60
Search For All Instances Of A Word ...60
Chapter 7 ... 63
Troubleshooting Linux With Syslog... 63
Syslog ...63
About syslog ...63
Syslog Facilities...64
Activating Changes To The syslog Configuration File...65
How To View New Log Entries As They Happen...65
Logging Syslog Messages To A Remote Linux Server...65
Configuring the Linux Syslog Server...65
Configuring the Linux Client ...66
Syslog Configuration and Cisco Network Devices...67
Syslog and Firewalls...67
Logrotate ...67
The /etc/logrotate.conf File ...67
Sample contents of /etc/logrotate.conf ...68
The /etc/logrotate.d Directory...68
The /etc/logrotate.d/syslog File (For General System Logging)...68
The /etc/logrotate.d/apache File (For Apache) ...69
The /etc/logrotate.d/samba File (for SAMBA) ...69
Activating logrotate ...69
Chapter 8 ... 71
Linux Networking ... 71
How To Configure Your NIC's IP Address ...71
Determining Your IP Address...71
Changing Your IP Address ...72
network-scripts File Formats ...73
Multiple IP Addresses On A Single NIC ...73
IP Address Assignment For A Direct DSL Connection...74
Some Important Files Created By adsl-setup ...77
Simple Troubleshooting ...78
How To Change Your Default Gateway ...79
How Configure Two Gateways ...79
How To Delete A Route ...80
How To View Your Current Routing Table ...80
How To Convert Your Linux Server Into A Router ...81
Configuring Your /etc/hosts File...82
Chapter 9 ... 85
Simple Network Troubleshooting ... 85
How To See MAC Addresses ...85
How To Use "Ping" To Test Network Connectivity ...86
Using "traceroute" To Test Connectivity...87
Possible Traceroute Messages...88
Always Get A Bidirectional Traceroute ...89
Ping & Traceroute Troubleshooting Example ...90
Possible Reasons For Failed Traceroutes ...91
Viewing Packet Flow With TCPdump ...92
Possible TCPdump Messages...92
Useful TCPdump Expressions ...93
Chapter 10... 97
Linux Wireless Networking... 97
Wireless Linux Compatible NICs ...97
The Linksys WMP11 NIC and Linux ...98
Pre Version 2.7 WMP 11 Card...98
The WMP 11 Version 2.7 Card ...98
Linux-WLAN Preparation ...99
PCMCIA Type Card Specific Information ...99
Installing The Linux-WLAN Drivers ...99
Linux-WLAN Installation - Using RPMs ...99
Determining The Kernel Type ...99
Determining The OS Version ...100
Determining The Kernel Version...100
Linux-WLAN Installation – Using TAR files ...101
Install the Kernel Source Files ...101
Download And Install The Linux-WLAN TAR File ...101
Configure The New wlan0 Interface Driver (PCI Cards) ...102
Configure The New wlan0 Interface Driver (PCMCIA Cards) ...103
Post Installation Steps...104
Configure The New wlan0 Interface...104
Disable Your Existing Ethernet NIC ...104
Select the Wireless mode and SSID ...104
Simulate a Reboot ...105
PCI Cards – Installed Using RPMs ...105
PCI Cards – Installed Using TAR Files...105
PCMCIA Cards ...105
Check For Interrupt Conflicts...105
Linux-WLAN Encryption For Security ...107
De-activating Encryption ...108
Troubleshooting Your Wireless LAN ...109
Chapter 11... 111
Linux Firewalls Using iptables... 111
What Is iptables?...112
Download And Install The Iptables Package ...112
How To Get iptables Started ...112
Packet Processing In iptables ...112
Processing For Packets Routed By The Firewall...114
Packet Processing For Data Received By The Firewall...115
Packet Processing For Data Sent By The Firewall ...116
Targets And Jumps...117
Table Of Contents v
Important Iptables Command Switch Operations...119
General Iptables Match Criteria ...119
Common TCP and UDP Match Criteria ...120
Common ICMP (Ping) Match Criteria ...121
Common Match Extensions Criteria...121
Using User Defined Chains ...123
Sample iptables Scripts...124
Basic Initialization...124
Allowing DNS Access To Your Firewall ...125
Allowing WWW And SSH Access To Your Firewall...126
Allowing Your Firewall To Access The Internet...126
Allow Your Home Network To Access The Firewall ...127
Masquerading (Many to One NAT) ...127
Port Forwarding Type NAT (DHCP DSL) ...128
Static NAT ...130
Logging & Troubleshooting...131
Chapter 12... 133
Telnet, TFTP and XINETD ... 133
Telnet ...134
What is Telnet? ...134
Setting Up A Telnet Server...135
TFTP ...135
What is TFTP?...135
Setting up a TFTP server...136
Configuring Cisco Devices for TFTP...137
Cisco PIX firewall ...137
Cisco Switch Running CATOS...137
Cisco Router ...138
Cisco CSS 111000 "Arrowpoints"...138
Cisco Local Director...138
Using TFTP To Restore Your Router Configuration ...139
Chapter 13... 141
Linux FTP Server Setup... 141
FTP Overview...141
FTP Control Channel - TCP Port 21 ...142
FTP Data Channel - TCP Port 20...142
Active FTP...142
Passive FTP...143
Problems With FTP And Firewalls...143
Client Protected By A Firewall Problem...143
Solutions...143
Server Protected By A Firewall Problem ...144
Solutions...144
How To Download And Install The VSFTP Package...145
How To Get VSFTP Started ...146
Testing To See If VSFTP Is Running...146
What Is Anonymous FTP?...147
The /etc/vsftpd.conf File...147
FTP Security Issues ...148
The /etc/vsftpd.ftpusers File ...148
Anonymous Upload ...148
FTP Greeting Banner ...148
Using SCP As Secure Alternative To FTP ...148
Sample Login Session To Test Funtionality...150
Chapter 14... 153
Secure Remote Logins And File Copying... 153
Using Secure Shell As A Replacement For Telnet ...153
Testing To See If SSH Is Running ...154
The etc/ssh/sshd_config File...154
Using SSH To Login To A Remote Machine ...155
User “root” Logs In To smallfry As User “root”...155
User “root” Logs In To smallfry As User “peter” ...155
Using default port 22 ...155
Using port 435 ...155
What You Should Expect To See When You Log In ...155
Deactivating Telnet once SSH is installed ...156
Using SCP as a more secure replacement for FTP...157
Copying Files To The Local Linux Box ...157
Copying Files To The Remote Linux Box...157
Chapter 15... 159
Windows, Linux And Samba ... 159
Download and Install Packages...160
How To Get SAMBA Started...160
Configuring SWAT ...161
Samba and PC Firewall Software...161
Zone Alarm...162
The Windows XP Built In Firewall...162
How To Create A Samba PDC Administrator User ...162
Create The Administrator’s User Group and Directories ...162
Create The Administrator User Under Linux...163
Adduser’s Command Switches ...163
Create An Administrator Domain Password ...164
Make The Administrator One Of The Samba Admin Users...164
How to Configure a Samba PDC...164
Create A Samba PDC ...164
Create Your PC Machine Trusts...166
Manual Creation Of Machine Trust Accounts (NT Only)...166
Dynamic Creation Of Machine Trust Accounts...167
Make Your PC Clients Aware Of Your Samba PDC...167
Windows 95/98/ME...167
Windows NT...168
Windows 2000 ...168
Windows XP...168
How To Add Users To Your Samba Domain ...169
Add The Users In Linux...169
Map The Linux Users To An smbpassword ...169
Map A Drive Share...169
Mapping Using “My Computer” ...169
Mapping From The Command Line...170
Domain Groups And Samba ...170
How To Delete Users From Your Samba Domain ...171
Delete The Users In Linux ...171
Delete The Users Using smbpasswd...171
Chapter 16... 173
Table Of Contents vii
Adding A Printer To A Samba PDC ...173
Adding The Printer To Linux...173
Make Samba Aware Of The Printer ...174
Configure The Printer Driver On The Workstations ...175
Creating Group Shares in SAMBA ...176
Create The Directory And User Group ...176
Configure The Share In SWAT ...176
Map The Directory Using “My Computer”...177
Windows Drive Sharing With Your SAMBA Server ...177
Windows Setup ...177
Windows 98/ME ...177
Windows 2000 ...177
Windows XP...178
Test Your Windows Client Configuration...178
Create A ZIP Drive Mount Point On Your Samba Server ...178
Prompted For Password Method ...179
Not Prompted For Password Method...179
Using The smbmount Command Method...179
Chapter 17... 181
Configuring DNS... 181
What Is DNS?...181
What Is BIND?...181
When To Use A DNS Caching Nameserver ...182
When To Use A Regular DNS Server...182
When To Use Dynamic DNS...182
How To Download and Install The BIND Packages ...182
How To Get BIND Started ...182
The /etc/resolv.conf File...183
Configuring A Caching Nameserver...184
Configuring A Regular Nameserver ...184
Configuring named.conf...184
Configuring The Zone Files ...185
The SOA Record...185
NS, MX, A And CNAME Records ...187
Sample Forward Zone File ...188
Sample Reverse Zone File ...189
What You Need To Know About NAT And DNS ...189
Loading Your New Configuration Files ...192
Make Sure Your /etc/hosts File Is Correctly Updated...192
Configure Your Firewall...192
Fix Your Domain Registration ...193
How To Migrate Your Website In-House...193
DHCP Considerations For DNS...194
Chapter 18... 197
Dynamic DNS... 197
What Is DNS?...197
What Is Dynamic DNS? ...198
Dynamic DNS And NAT Router/Firewalls ...198
Dynamic DNS Prerequisites...199
Sign Up With A DDNS Provider ...199
Update Your DNS Registration ...199
Installing And Using ez-ipupdate ...199
The /etc/ez-ipupdate.conf File...200
The /etc/ddclient.conf File...201
Testing Your Dynamic DNS ...202
Testing Port Forwarding...202
Chapter 19... 203
The Apache Web Server ... 203
Download and Install The Apache Package ...203
How To Get Apache Started ...204
Configuring DNS For Apache...204
General Configuration Steps...204
Named Virtual Hosting ...205
IP Based Virtual Hosting ...205
A Note On Virtual Hosting And SSL...205
Disabling SSL – (Not Recommended) ...206
Use Wild Cards Sparingly...206
Configuration – Multiple Sites And IP Addresses...206
A Note On Virtual Hosting And DNS ...208
Using Data Compression On Web Pages...208
Compression Configuration Example ...209
Apache Running On A Server Behind A Firewall...210
File Permissions And Apache ...210
How To Protect Web Page Directories With Passwords ...210
Issues When Upgrading To Apache 2.0...212
Incompatible /etc/httpd/conf/http.conf files ...212
Chapter 20... 213
Monitoring Server Performance ... 213
SNMP...213
What is SNMP? ...213
SNMP on a Linux Server ...213
MRTG ...215
What is MRTG?...215
Download and Install The MRTG Packages...215
Configuring MRTG ...216
RedHat Version 8.0 and Indexmaker...217
Using MRTG To Monitor Other Subsystems ...218
Webalizer ...218
What Is Webalizer?...218
How To View Your Webalizer Statistics ...218
The Webalizer Configuration File ...218
Make Webalizer run in Quiet Mode ...218
Chapter 21... 221
Configuring Linux Mail Servers... 221
Configuring Sendmail ...221
An Overview Of How Sendmail Works ...221
Configuring DNS ...222
Installing And Starting Sendmail...222
Restart Sendmail After Editing Your Configuration Files ...223
Errors With The Newaliases Command...223
Errors With The m4 Command ...223
Errors When Restarting sendmail...224
The /var/log/maillog File...224
The /etc/mail/sendmail.mc File ...224
Table Of Contents ix
Edit /etc/mail/sendmail.mc To Make Sendmail Listen On NICs Too...225
Regenerate The sendmail.cf File...225
Restart sendmail to load the new configuration ...226
Now Make Sure Sendmail Is Listening On All Interfaces...226
A General Guide To Using The sendmail.mc File...226
The /etc/hosts File...227
Symptoms Of A Bad /etc/hosts File...227
The /etc/mail/relay-domains File...228
The /etc/mail/access File ...229
The /etc/mail/local-host-names File...230
Which User Should Really Receive The Mail? ...230
The /etc/mail/virtusertable file ...231
The /etc/aliases File...231
Simple Mailing Lists Using Aliases...232
An Important Note About The /etc/aliases File ...233
Sendmail Masquerading Explained...233
Configuring masquerading...233
Testing Masquerading...234
Other Masquerading Notes ...234
A Simple PERL Script To Help Stop SPAM...235
Configuring Your POP Mail Server...235
Installing Your POP Mail Server ...236
Configuring Your POP Mail Server...236
How To Configure Your Windows Mail Programs...237
How to handle overlapping email addresses. ...237
Chapter 22... 239
Configuring The DHCP Server ... 239
Download and Install The DHCP Package ...239
The /etc/dhcp.conf File...240
Upgrading Your DHCP Server ...241
How to get DHCP started ...242
Modify Your Routes for DHCP on Linux Server ...242
Temporary solution ...242
Permanent Solution ...243
Configuring Linux clients to use DHCP ...243
Error Found When Upgrading From Redhat 7.3 To 8.0...243
Chapter 23... 245
The NTP Server ... 245
What is NTP?...245
Download and Install The NTP Package...246
The /etc/ntp.conf File ...246
How To Get NTP Started...247
Determining If NTP Is Synchronized Properly ...248
Configuring Cisco Devices To Use An NTP Server...248
Cisco IOS ...248
CAT OS ...249
Firewalls and NTP...249
Chapter 24... 251
Configuring Cisco PIX Firewalls... 251
Network Address Translation (NAT) ...251
Accessing the PIX command line ...252
Via The Console Port ...252
Configuring PPPoE...253
NAT Configuration ...254
Dynamic DNS Port Forwarding Entries ...254
How To Get Static IPs For DSL Cheaply ...254
Sample PIX configuration: DSL - Static IPs ...255
Outgoing Connections NAT Configuration ...255
Incoming Connections NAT Configuration ...255
Chapter 25... 257
Configuring Cisco DSL Routers ... 257
An Introduction to Network Address Translation (NAT) ...258
Introduction to accessing the router command line ...258
Via The Console Port ...258
Via Telnet ...258
Sample Configurations...260
DSL Router With Built-In Modem - DHCP...260
DSL Router With Built-In Modem - Static IP ...262
DSL Router With External Modem - Static IP ...264
Other NAT Topics ...266
Commonly Used TCP And UDP Ports...266
How To Verify That NAT Is Working Correctly ...266
How To Troubleshoot NAT ...267
Appendix I ... 269
Miscellaneous Topics... 269
VPN Terminologies...269 Authentication...269 Encryption ...270 IPSec ...270Authentication Header (AH)...270
Encapsulating Security Protocol (ESP) ...270
Transport mode VPNs...270
Transport mode AH packet format ...270
Transport mode AH / ESP packet format ...270
Tunnel mode VPNs...271
Tunnel mode AH packet format ...271
Tunnel mode AH / ESP packet format...271
Authentication methods...271
Encryption methods ...271
Internet Key Exchange (IKE)...271
IKE authentication methods...272
Public key cryptography using RSA encryption...272
Shared keys ...272
IKE's role in creating Security Associations ...273
Transforms ...273
Shared keys ...273
IKE and ISAKMP...273
VPN Security And Firewalls...273
VPN User Authentication Methods For Temporary Connections ...273
Types Of Dial Up VPN Authentication ...274
Running Linux Without A Monitor ...275
Preparing To Go “Headless” ...275
Configuration Steps ...275
Make Your Linux Box Emulate A VT100 Dumb Terminal...277
Table Of Contents xi
Syslog Configuration and Cisco Devices ...280
Cisco Routers ...280
Catalyst CAT Switches running CATOS...280
Cisco Local Director...280
Cisco PIX Filewalls ...282
Cisco CSS11000 (Arrowpoints) ...282
The Sample Cisco syslog.conf File ...283
Disk Partitioning Explained...284
What Is A Partition? ...284
What Is A Filesystem?...284
How Linux Links Filesystems And Partitions ...284
What Partitions Are Mandatory?...285
"/", Also Known As "root"...285
/boot ...285
swap...285
Recommended Sizes For Disk Partitions...285
Some Recommended Partition Sizes ...286
How Much Space Do I Have On My Partitions?...287
What Can I Do When I Run Out Of Disk Space?...287
The OSI Networking Model ...288
The Seven OSI Layers ...288
TCP/IP Packet Format ...289
Contents Of The IP Header ...289
Contents Of The TCP Header...290
Contents Of The UDP Header ...290
Appendix II... 293
Codes, Scripts and Configurations ... 293
Subnet Calculator Script ...294
Apache File Permissions Script ...296
Sendmail SPAM Filter Script...297
The mail-filter.accept File...298
The mail-filter.reject File...298
The mail-filter Script...298
IPtables FTP Client...303
IPtables FTP Server ...304
IPtables NTP Server...305
IPtables Complex script ...305
DNS Zone File For my-site.com ...319
DNS Zone File For my-other-site.com ...319
Forward Zone File For A Home Network Using NAT ...320
Reverse Zone File For A Home Network Using NAT ...320
Sendmail Sample /etc/mail/access File ...322
Sendmail Sample /etc/aliases File ...322
Sendmail Sample /etc/mail/local-host-names File ...323
Sendmail Sample /etc/mail/sendmail.mc File ...324
Sendmail Sample /etc/mail/virtusertable File...326
ICMP Codes...327
Cisco PIX Firewall - DHCP DSL Configuration...329
Cisco PIX Firewall - Static DSL Configuration...330
Appendix III... 333
Bibliography ... 333
Wireless Linux ...334
Cisco Router Configuration Examples...334
General Home Networking Resource Pages...335
SSH Servers and SSH Clients...335
The Windows SCP client called WinSCP...336
FTP Server and FTP Clients ...336
DHCP Server ...336
Apache Web Server Software...336
Sendmail Mail Configuration ...336
Dynamic DNS - Hosting Your Website at Home ...337
Static DNS...337
NTP Server ...337
POP Mail Server ...338
Samba - Linux as a Windows File Server ...338
General Linux Resource Pages...338
Disk Partitioning ...339
Network Monitoring...339
15
Chapter 1
Adding Linux Users
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
In This Chapter
Chapter 1
Adding Linux Users
Who Is The Super User? How To Add UsersHow To Change Passwords How To Delete Users
How To Tell The Groups To Which A User Belongs
© Peter Harrison, www.linuxhomenetworking.com
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
O
ne of the most important activities in administering a Linux box is the addition of users. I have included some simple examples to provide a foundation for future chapters. A more detailed description of the process is beyond the focus of this book. You may use the command “man useradd” to get the help pages on adding users with the useradd command or the “man usermod” to become more familiar with modifying users with the usermod command.Who Is The Super User?
The super user with unrestricted access to all system resources and files is the user named "root". You will need to log in as user root to add new users to your Linux box
How To Add Users
Adding users takes some planning, read through the steps below before starting:
• Arrange your list of users into groups by function. In this example there are three groups "parents", "children" and "soho".
Parents Children Soho
Paul Alice Accounts Jane Derek Sales • Add the Linux groups to your server:
[root@bigboy tmp]# groupadd parents [root@bigboy tmp]# groupadd children [root@bigboy tmp]# groupadd soho
• Add the Linux users, assign them to their respective groups [root@bigboy tmp]# useradd -g parents paul [root@bigboy tmp]# useradd -g parents jane [root@bigboy tmp]# useradd -g children derek [root@bigboy tmp]# useradd -g children alice [root@bigboy tmp]# useradd -g soho accounts [root@bigboy tmp]# useradd -g soho sales
If you don't specify the group with the "-g", RedHat Linux will create a group with the same name as the user you just created. When each new user first logs in, they will be prompted for their new permanent password.
• Each user's personal directory will be placed in the /home directory. The directory name will be the same as their user name.
[root@bigboy tmp]# ll /home
drwxr-xr-x 2 root root 12288 Jul 24 20:04 lost+found drwx--- 2 accounts soho 1024 Jul 24 20:33 accounts drwx--- 2 alice children 1024 Jul 24 20:33 alice drwx--- 2 derek children 1024 Jul 24 20:33 derek drwx--- 2 jane parents 1024 Jul 24 20:33 jane drwx--- 2 paul parents 1024 Jul 24 20:33 paul drwx--- 2 sales soho 1024 Jul 24 20:33 sales [root@bigboy tmp]# ll /home
How To Change Passwords
You’ll need to create passwords for each account. This is done with the "passwd" command. You will be prompted once for your old password and twice for the new one.
• User "root" changing the password for user "paul" [root@bigboy root]# passwd paul Changing password for user paul. New password:
Chapter 1 : Adding Linux Users 17
passwd: all authentication tokens updated successfully. [root@bigboy root]#
• Users may wish to change their passwords at a future date. Here is how unprivileged user "paul" would change his own password.
[paul@bigboy paul]$ passwd Changing password for paul
Old password: your current password
Enter the new password (minimum of 5, maximum of 8 characters)
Please use a combination of upper and lower case letters and numbers. New password: your new password
Re-enter new password: your new password Password changed.
[paul@bigboy paul]$
How To Delete Users
• The userdel command is used. The "-r" flag removes all the contents of the user's home directory [root@bigboy tmp]# userdel -r paul
How To Tell The Groups To Which A User Belongs
• Use the "groups" command with the username as the argument [root@bigboy root]# groups paul
paul : parents
[root@bigboy root]#
Chapter 1 : Adding Linux Users 19
Chapter 2
Using Sudo
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =In This Chapter
Chapter 2
Using Sudo
What is sudo?Download and Install The sudo Package The visudo Command
The /etc/sudoers File How To Use sudo
Using syslog To Track All sudo Commands
© Peter Harrison, www.linuxhomenetworking.com
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
Y
ou can give selected users temporary "root" privileges using the "sudo" command, here's how.What is sudo?
• Sudo is a command that allows users defined in the /etc/sudoers configuration file to have temporary root access to run certain privileged commands.
• The command you want to run must first begin with the word "sudo" followed by the regular command syntax.
• You may run other privileged commands using sudo within a five minute period without being re-prompted for a password
• All commands run as sudo are logged in the log file /var/log/messages
Download and Install The sudo Package
Fortunately the package is installed by default by RedHat
The visudo Command
• "visudo" is the command used to edit the /etc/sudoers configuration file. It is not recommended that you use any other editor to modify your sudo parameters. "visudo" uses the same commands as the "vi" text editor.
• "visudo" is best run as user "root"
The /etc/sudoers File
General Guidelines
o The /etc/sudoers file has the general format:
usernames/group target-servername = command
o Groups are the same as user groups and are differentiated from regular users by a % at the beginning
o The "#" at the beginning of a line signifies a comment line o You can have multiple usernames per line separated by commas
o Multiple commands can be separated by commas too. Spaces are considered part of the command.
o The keyword "ALL" can mean all usernames, groups, commands and servers.
o If you run out of space on a line, you can end it with a "\" and continue on the next line. o The NOPASSWD keyword provides access without you being prompted for your password
Simple Examples
o Users "paul" and "mary" have full access to all privileged commands
Chapter 2 : Using Sudo 21
o Users with a groupid of "operator" has full access to all commands and won't be prompted for a password when doing so.
%operator ALL=(ALL) NOPASSWD: ALL
How To Use sudo
• In this example, user "paul" attempts to view the contents of the /etc/sudoers file
[paul@bigboy paul]$ more /etc/sudoers /etc/sudoers: Permission denied
[paul@bigboy paul]$
• Paul tries again using sudo and his regular user password and is successful
[paul@bigboy paul]$ sudo more /etc/sudoers Password: ... ... ... [paul@bigboy paul]$
Using syslog To Track All sudo Commands
All sudo commands are logged in the log file /var/log/messages. Here is sample output from the above example.
[root@bigboy tmp]# grep sudo /var/log/messages
Nov 18 22:50:30 bigboy sudo(pam_unix)[26812]: authentication failure; logname=paul uid=0 euid=0 tty=pts/0 ruser= rhost= user=paul
Nov 18 22:51:25 bigboy sudo: paul : TTY=pts/0 ; PWD=/etc ; USER=root ; COMMAND=/bin/more sudoers
23
Chapter 3
Installing RPM Software
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =In This Chapter
Chapter 3
Installing RPM Software
Where To Get Commonly Used RPMs
How to Easily Access CD RPMs With Automount Downloading RPMS To Your Linux Box
Getting RPMs Using Web Based FTP
Getting RPMs Using Command Line Anonymous FTP How To Install The RPMs
How to Install Source RPMs How To List Installed RPMs How Uninstall RPMs RedHat Up2date
© Peter Harrison, www.linuxhomenetworking.com
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
A
lot of Linux system software is available using RPM packages for default Linux installs, and source RPMs for non standard installations. As the procedure for installing source RPMs involves compiling source code, they more easily installed across a wide variety of Linux flavors, thereby making life easier for the software developer who wrote the package.Where To Get Commonly Used RPMs
RPMs On Your Installation CDs
This is usually easier than having to download files from a remote website. See the section about using Automount to easily access your CDROM drive to obtain RPM files.
RPMs Downloaded From Redhat
Advanced searches for all versions of RedHat can be done using this web link:
http://www.redhat.com/apps/download/advanced_search.html
RedHat also has a highly used FTP site, ftp.redhat.com, start your search in the /pub/redhat/linux/ directory and move down the directory tree. If you’re new to FTP, don’t worry, FTP downloading it’ll be explained later.
RPMs Downloaded From Speakeasy
RedHat only has their approved software on their site. A good general purpose source is RPMfind. Always remember to select the RPM that matches your version of Linux
http://speakeasy.rpmfind.net/
How to Easily Access CD RPMs With Automount
Using the Linux installation CDs is usually easier, though you run the risk of some of the packages being obsolete due to newer releases on the RedHat website.
It is usually simplest to configure your system to Automount your CDROM. This makes the files on it immediately accessible whenever you access it without having to use the "mount" command. This will make your Linux system act more like Windows.
• Autofs is the package that supports Automount is installed by default with newer versions of RedHat Linux. You can check this using the following commands.
[root@bigboy tmp]# rpm -qa | grep autofs autofs-3.1.7-33
[root@bigboy tmp]#
• You can then ensure that it runs when the system boots using the chkconfig command.
[root@bigboy tmp]# chkconfig --level 345 autofs on [root@bigboy tmp]#
Chapter 3 : Installing RPM Software 25
• There are two automount configuration files in /etc, one called auto.master and the other called auto.misc. My auto.master looks like this:
/misc /etc/auto.misc --timeout 60
The default version of this file normally has this line commented out so you’ll have to remove the "#" at the beginning of the line for the configuration to take effect when autofs is restarted. The first entry is not the mount point. It's where the set of autofs mount points will be. The second entry is a reference to the default map file /etc/auto.misc and the third option says that the mounted
filesystems can try to unmount themselves 60 seconds after use.
• You can create mount points for each of your removable devices, "floppy", "cdrom" and "zip" with the following commands.
[root@bigboy tmp]# mkdir /misc/cdrom [root@bigboy tmp]# mkdir /misc/floppy [root@bigboy tmp]# mkdir /misc/zip [root@bigboy tmp]# ll /misc
total 3
drwxr-xr-x 2 root root 1024 Nov 10 16:06 cdrom drwxr-xr-x 2 root root 1024 Nov 10 16:06 floppy drwxr-xr-x 2 root root 1024 Nov 10 16:06 zip [root@bigboy tmp]#
• Edit your auto.misc file to include the CDROM. It should have an entry like this.
cdrom -fstype=iso9660,ro,nosuid,nodev :/dev/cdrom
You'll find other entries such as "floppy" and "zip" commented out with a "#". If you need them, just delete the "#". The first column (the "key") is the mount point under directory /misc, so in this case you'll be doing auto mounting when you access /misc/cdrom.
• Restart autofs.
[root@bigboy /tmp]# /etc/init.d/autofs restart Stopping automount:[ OK ]
Starting automount:[ OK ] [root@bigboy /tmp]#
Downloading RPMS To Your Linux Box
For casual searching and installing, I recommend using the http links above. If you are doing industrial strength stuff, then use a real FTP client such as (WSFTP or CuteFTP for GUI) or the command line.
Getting RPMs Using Web Based FTP
Let’s say you are running RedHat 8.0 and need to download an RPM for the DHCP server.
RedHat
• Use your web browser to go to the RedHat link above • Type in dhcp in the search box
• Click the search button
• Scroll down for the RPM you need for the DHCP server • Click on the appropriate "download" link
• Click on the FTP link
• Save the file to Linux box's hard drive
Speakeasy
• Go to the Speakeasy link • Type in dhcp in the search box • Click the search button
• Scroll down for the RPM that matches your version of RedHat
• The right hand column has the links with the actual names of the rpm files • Click the link
• Save the file to Linux box's hard drive
It is best to download RPMs to a directory named "RPM", so you can find them later.
Getting RPMs Using Command Line Anonymous FTP
The Web based method above transparently uses anonymous File Transfer Protocol (FTP). Anonymous FTP allows you to log in and download files from a FTP server using the username
“anonymous” and a password that matches your email address. This way anyone can access the data.
• Let's try to FTP the SSH package from ftp.redhat.com
[root@bigboy tmp]# ftp ftp.redhat.com Trying 66.77.185.38...
Chapter 3 : Installing RPM Software 27
220 Red Hat FTP server ready. All transfers are logged. Name (ftp.redhat.com:root): anonymous
331 Please specify the password. Password:
230 Login successful. Have fun. Remote system type is UNIX.
Using binary mode to transfer files. ftp> ls
227 Entering Passive Mode (66,77,185,38,50,122) 150 Here comes the directory listing.
drwxr-xr-x 5 0 0 4096 Jun 09 04:20 pub 226 Directory send OK.
ftp>
• Let's see the available help commands
ftp> help
Commands may be abbreviated. Commands are: ! $ account append ascii bell binary bye case cd cdup chmod close cr delete debug dir disconnect exit form get glob hash help idle image lcd ls macdef Mdelete mdir mget mkdir mls mode modtime mput newer nmap nlist ntrans open prompt passive proxy sendport put pwd quit quote recv reget rstatus rhelp rename reset restart rmdir runique send site size status struct system sunique tenex tick trace type user umask verbose ? ftp>
• The commands you'll most likely use are:
FTP Commands
Command Description
binary Copy files in binary mode
cd Change directory on the FTP server
dir List the names of the files in the current remote directory
Command Description
get Get a file from the FTP server
lcd Change the directory on the local machine ls Same as dir
mget Same as get, but you can use wildcards like "*" mput Same as put, but you can use wildcards like "*" passive Make the file transfer passive mode
put Put a file from the local machine onto the FTP server pwd Give the directory name on the local machine
• By using the search feature on the website ahead of time, I know that the RedHat 8.0RPMs are located in the pub/redhat/linux/8.0/en/os/i386/RedHat/RPMS directory.
ftp> cd pub/redhat/linux/8.0/en/os/i386/RedHat/RPMS 250 Directory successfully changed.
ftp> ls open*
227 Entering Passive Mode (66,77,185,38,45,180) 150 Here comes the directory listing.
-rw-r--r-- 1 0 0 11191 Sep 03 21:32 open-1.4-16.i386.rpm -rw-r--r-- 1 0 0 2006950 Sep 03 21:32 openh323-1.9.3-4.i386.rpm -rw-r--r-- 1 0 0 256971 Sep 03 21:32 openh323-devel-1.9.3-4.i386.rpm ... ... -rw-r--r-- 1 0 0 217326 Sep 03 21:33 openssh-3.4p1-2.i386.rpm ... ...
226 Directory send OK. ftp>
• Get the file we need and place it in the local directory /usr/rpm. Also print "#" hash signs on the screen during the download.
ftp> hash
Hash mark printing on (1024 bytes/hash mark). ftp> lcd /usr/rpm
Local directory now /usr/rpm ftp>
ftp> get openssh-3.4p1-2.i386.rpm
local: openssh-3.4p1-2.i386.rpm remote: openssh-3.4p1-2.i386.rpm 227 Entering Passive Mode (66,77,185,38,57,102)
150 Opening BINARY mode data connection for openssh-3.4p1-2.i386.rpm (217326 bytes).
##################################################################### #####################################################################
Chapter 3 : Installing RPM Software 29
#################################################################### 226 File send OK.
217326 bytes received in 87.7 secs (2.4 Kbytes/sec) ftp> • Bye bye ftp> exit 221 Goodbye. [root@bigboy tmp]#
How To Install The RPMs
Using Downloaded Files
• Download the source RPMs which usually have a file extension ending with (.rpm) into a temporary directory such as /tmp
• As user root, issue the following command:
[root@bigboy tmp]# rpm -Uvh filename.rpm
Using CDROMs
• Insert the CDROM and check the files in /misc/cdrom/RedHat/RPMS
[root@bigboy tmp]# cd /misc/cdrom/RedHat/RPMS [root@bigboy RPMS]# ls filename*
filename.rpm
[root@bigboy RPMS]# rpm -Uvh filename.rpm
• When finished, eject the CDROM
[root@bigboy RPMS]# cd /tmp [root@bigboy tmp]# eject cdrom [root@bigboy tmp]#
How to Install Source RPMs
Sometimes the packages you want to install need to be compiled in order to match your kernel version. This requires you to use source RPM files.
• Download the source RPMs or locate them on your CD collection. They usually have a file extension ending with (.src.rpm)
• Run the following commands as root:
Newer Linux Versions
Compiling and installing source RPMs with newer RedHat Linux versions can be done simply with the rpmbuild command
[root@bigboy tmp]# rpmbuild --rebuild filename.src.rpm
o Here is an example in which we install the tacacs plus package.
[root@bigboy rpm]# rpmbuild --rebuild tac_plus-4.0.3-2.src.rpm Installing tac_plus-4.0.3-2.src.rpm
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.61594 + umask 022 + cd /usr/src/redhat/BUILD + cd /usr/src/redhat/BUILD + rm -rf tac_plus-4.0.3 + /usr/bin/gzip -dc /usr/src/redhat/SOURCES/tac_plus-4.0.3.tgz + tar -xvvf - drwxr-xr-x nsen/25 0 1999-08-04 00:33:15 tac_plus-4.0.3/ -rw-r--- root/root 9029 1999-04-02 22:03:45 tac_plus-4.0.3/CHANGES ... ... ... ... ... ...
Checking for unpackaged file(s): /usr/lib/rpm/check-files /var/tmp/tacacsd
Wrote: /usr/src/redhat/RPMS/i386/tac_plus-4.0.3-2.i386.rpm Executing(%clean): /bin/sh -e /var/tmp/rpm-tmp.60207
+ umask 022
+ cd /usr/src/redhat/BUILD + cd tac_plus-4.0.3
+ rm -rf /var/tmp/tacacsd + exit 0
Executing(--clean): /bin/sh -e /var/tmp/rpm-tmp.60207 + umask 022
+ cd /usr/src/redhat/BUILD + rm -rf tac_plus-4.0.3 + exit 0
[root@bigboy rpm]#
o Here we see that the regular RPM file, not the source RPM, has been installed correctly. [root@bigboy rpm]# rpm -qa | grep tac_plus
tac_plus-4.0.3-2 [root@bigboy rpm]#
Chapter 3 : Installing RPM Software 31
Older Linux Versions
The process is more complicated with older RedHat Linux versions as can be seen below. o The source files are first exported into the directory /usr/src/redhat/SPECS with the rpm
command.
o You then have to run the rpm command again to compile the source files into a regular RPM file which will be placed in either the /usr/src/packages/RPMS/i386/ or the
/usr/src/redhat/RPMS/i386/ directories.
o You then have to install the new RPM file from this directory.
[root@bigboy tmp]# rpm -Uvh filename.src.rpm [root@bigboy SPECS]# cd /usr/src/redhat/SPECS [root@bigboy SPECS]# rpm –ba filename
[root@bigboy tmp]# cd /usr/src/redhat/RPM/i386 [root@bigboy i386]# rpm -Uvh filename.rpm
How To List Installed RPMs
• The rpm –qa command will list all the packages installed on your system [root@bigboy tmp]# rpm –qa perl-Storable-1.0.14-15 smpeg-gtv-0.4.4-9 e2fsprogs-1.27-9 libstdc++-3.2-7 audiofile-0.2.3-3 … … … [root@bigboy tmp]#
• You can also pipe the output of this command through the grep command if you are interested in only a specific package. In this example we are looking for all packages containing the string “ssh” in the name, regardless of case (“-i” meaning ignore case)
[root@bigboy tmp]# rpm -qa | grep -i ssh openssh-server-3.4p1-2 openssh-clients-3.4p1-2 openssh-askpass-gnome-3.4p1-2 openssh-3.4p1-2 openssh-askpass-3.4p1-2 [root@bigboy tmp]#
How Uninstall RPMs
• The rpm –e command will erase an installed package. The package name given must match that listed in the rpm –qa command as the version of the package is important.
[root@bigboy tmp]# rpm –e package-name
RedHat Up2date
RedHat has a program called up2date which will update your Linux installation with the latest revisions of the RPMs from the RedHat website via a HTTPS/SSL connection running in the background. Here’s what to do:
• After installing the operating system issue the up2date command. It will prompt you to change the initial settings. Just quit by typing “q” and up2date will give you the command to run to get the encryption keys from RedHat.
[root@bigboy tmp]# up2date 0. debug No 1. isatty Yes 2. depslist [] … … …
Enter number of item to edit <return to exit, q to quit without saving>:
Your GPG keyring does not contain the Red Hat, Inc. public key. Without it, you will be unable to verify that packages Update Agent downloads are securely signed by Red Hat.
Your Update Agent options specify that you want to use GPG.
To install the key, run the following as root:
rpm --import /usr/share/rhn/RPM-GPG-KEY
[root@bigboy tmp]#
• Issue the rpm command to get the keys
[root@bigboy tmp]# rpm --import /usr/share/rhn/RPM-GPG-KEY [root@bigboy tmp]#
Chapter 3 : Installing RPM Software 33
• Issue the up2date command again and it will prompt you through a number of registration screens which will ask for information such as:
o The login name & password of your choice o Your, name, address and email address o A profile name for your server
• It will then present you with a list of all the packages installed on your server and ask you whether you want to register this software information with RedHat
• The up2date updater will then register your system and exit back to the command prompt. • Now you have to actually update the software using up2date. This is done with the up2date –u
command. This is what it looks like: [root@bigboy tmp]# up2date -u
Fetching package list for channel: redhat-linux-i386-8.0... ########################################
Fetching Obsoletes list for channel: redhat-linux-i386-8.0... ########################################
Fetching rpm headers...
#######################################
Testing package set / solving RPM inter-dependencies... ######################################## cups-libs-1.1.17-0.2.i386.r ########################## Done. … … … Preparing ########################################### [100%] Installing... 1:cups-libs ########################################### [100%] 2:cvs ########################################### [100%] 3:cyrus-sasl ########################################### [100%] … … …
The following Packages were marked to be skipped by your configuration:
Name Version Rel Reason
--- kernel 2.4.18 24.8.0Pkg name/pattern
Some Necessary Facts About up2date
o You can update your contact information afterwards using the link http://www.redhat.com/network
o RedHat will regularly send you emails with the packages you need to update. You can selectively update the package mentioned in each email using the command:
[root@bigboy tmp]# up2date package-name
o Only one profile per login name is free. All additional profiles under the login name have an annual fee.
o up2date uses HTTPS/SSL to do its updating. If you have a firewall protecting your system, you will need TCP port 443 access to the internet
o Updating packages could cause programs written by you to stop functioning especially if they rely on the older version’s features or syntax.
o Some RPMs won’t install unless other RPMs have been installed previously. up2date automatically figures out these package inter-dependencies and will install all the required foundation packages as well.
o You can write a small script to periodically update your system. The “–u” switch will update all packages and the “-p” will register any additional packages you have installed without using up2date. Here is a sample script that you can run weekly using cron
#!/bin/sh #
# Updates system every week #
up2date -p up2date -u
37
Chapter 4
The Linux Boot Process
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
In This Chapter
Chapter 4
The Linux Boot Process
The RedHat Boot SequenceDetermining The Default Boot runlevel Get A GUI Console
Get A Basic Text Terminal Without Exiting The GUI System Shutdown And Rebooting
How To Set Which Programs Run At Each runlevel
© Peter Harrison, www.linuxhomenetworking.com
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
T
he way Linux boots up is very important information to know. You can alter it to change the type of login screen you get and also which programs get started.
The RedHat Boot Sequence
When RedHat boots, the boot process will run a number of scripts located in subdirectories under directory /etc/rc.d. The boot process first runs the scripts found in /etc/rc.d/rc1.d which provides only the most basic functionality and the ability to only handle a single user. This stage is known as “single user mode”. After completing this first phase, the boot process will run scripts in only one of the other directories depending on the startup mode (aka. run level). These are listed below.
Mode/Run Level Directory Run Level Description 0 1 2 3 4 5 6 /etc/rc.d/rc0.d /etc/rc.d/rc1.d /etc/rc.d/rc2.d /etc/rc.d/rc3.d /etc/rc.d/rc4.d /etc/rc.d/rc5.d /etc/rc.d/rc6.d Halt Single-user mode Not used (user-definable)
Full multi-user mode (No GUI interface) Not used (user-definable)
Full multi-user mode (With GUI interface) Reboot
Determining The Default Boot runlevel
The default boot runlevel is set in the file /etc/inittab with the "initdefault" variable. When set it to “3”, the system boots up with the text interface on the VGA console; when set to “5”, you get the GUI. Here is a sample snippet of the file: (Delete the initdefault line you don't need)
# Default runlevel. The runlevels used by RHS are: # 0 - halt (Do NOT set initdefault to this)
# 1 - Single user mode
# 2 - Multiuser, without NFS (The same as 3, if you do not have networking)
# 3 - Full multiuser mode # 4 - unused
# 5 - X11
# 6 - reboot (Do NOT set initdefault to this) #
id:3:initdefault: # Console Text Mode
id:5:initdefault: # Console GUI Mode
• Most home users boot up with a Windows like GUI (Run Level 5)
• Most techies will tend to boot up with a plain text based command line type interface (Run level 3)
• Changing "initdefault" from 3 to 5 or vice-versa will only have an effect upon your next reboot. See the section below on how to get a GUI login all the time until the next reboot.
Get A GUI Console
You have two main options if your system comes up in a text terminal mode on the VGA console and you want to get the GUI:
• Manual Method: You can start the X terminal GUI application each time you need it by running the “startx” command at the VGA console. Remember that when you log out you will get the regular text based console again.
Chapter 4 : The Linux Boot Process
[root@bigboy tmp]# startx
• Automatic Method: You can have Linux automatically start the X terminal GUI console for every login attempt until your next reboot by using the init command. You will need to edit your “initdefault” variable in your /etc/inittab file as mentioned in the preceding section to keep this functionality even after you reboot.
[root@bigboy tmp]# init 5
Get A Basic Text Terminal Without Exiting The GUI
Using A GUI Terminal Window
You can open a GUI based window with a command prompt inside by doing the following: o Click on the “Red Hat” Start button in the bottom left hand corner of the screen. o Click on Systems Tools, then Terminal
Using Virtual Terminals
Linux actually has seven virtual console sessions running on the VGA console. o Sessions one through six are text sessions. If the GUI is running, it will run under
session number seven.
o You can step through each text session by using the <CTL> <ALT> <F1> through <F6> key sequence. You'll get a new login prompt for each attempt.
o You can get the GUI login with the sequence <CTL> <ALT> <F7>, only in run level 5, or if the GUI is running after launching "startx"
System Shutdown And Rebooting
The "init" command will allow you to change the current runlevel.
Halt / Shutdown The System
[root@bigboy tmp]# init 0
Reboot The System
[root@bigboy tmp]# init 6How To Set Which Programs Run At Each runlevel
Most RedHat packages place a startup script in the directory /etc/init.d and place symbolic links (pointers) to this script in the appropriate /etc/rc.d/rc.X directory. The typical home/SOHO user doesn't have to be a scripting / symbolic linking guru to make sure everything works right because RedHat comes with a nifty utility called "chkconfig" to do it for you.
• Use this command to get a full listing of packages listed in /etc/init.d and the runlevels at which they will be "on" or "off"
[root@bigboy tmp]# chkconfig --list
keytable 0:off 1:on 2:on 3:on 4:on 5:on 6:off atd 0:off 1:off 2:off 3:on 4:on 5:on 6:off syslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off gpm 0:off 1:off 2:on 3:on 4:on 5:on 6:off kudzu 0:off 1:off 2:off 3:on 4:on 5:on 6:off wlan 0:off 1:off 2:on 3:on 4:on 5:on 6:off sendmail 0:off 1:off 2:off 3:on 4:off 5:on 6:off netfs 0:off 1:off 2:off 3:on 4:on 5:on 6:off network 0:off 1:off 2:on 3:on 4:on 5:on 6:off random 0:off 1:off 2:on 3:on 4:on 5:on 6:off ...
...
Chkconfig Examples
You can use chkconfig to change runlevels for particular packages. Here we see
Sendmail will start with a regular startup at runlevel 3 or 5. Let’s change it so that Sendmail doesn't startup at boot.
Use Chkconfig To Get A Listing Of Sendmail's Current Startup Options
[root@bigboy tmp]# chkconfig --list | grep mailsendmail 0:off 1:off 2:off 3:on 4:off 5:on 6:off [root@bigboy tmp]#
Switch Off Sendmail Starting Up In Levels 3 and 5
[root@bigboy tmp]# chkconfig --level 35 sendmail off [root@bigboy tmp]#
Doublecheck That Sendmail Will Not Startup
[root@bigboy tmp]# chkconfig --list | grep mail sendmail 0:off 1:off 2:off 3:off 4:off 5:off 6:off [root@bigboy tmp]#
Chapter 4 : The Linux Boot Process
Turn it back on again
[root@bigboy tmp]# chkconfig --level 35 mail on [root@bigboy tmp]# chkconfig --list | grep mail sendmail 0:off 1:off 2:off 3:on 4:off 5:on 6:off [root@bigboy tmp]#
Final Tips On chkconfig
• In most cases you'll want to modify runlevels 3 and 5 simultaneously AND with the same values.
• Don't add/remove anything to other runlevels unless you absolutely know what you are doing. Don't experiment.
• Chkconfig doesn’t start the programs in the /etc/init.d directory, it just configures them to be started or ignored when the system boots up. The commands for starting and stopping the programs covered in this book are covered in each respective chapter.
43
Chapter 5
Why Host Your Own Site?
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =In This Chapter
Chapter 5
Why Host Your Own Site?
Network DiagramAlternatives To Home Web Hosting
Factors To Consider Before Hosting Yourself How To Migrate From An External Provider
© Peter Harrison, www.linuxhomenetworking.com
= = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
W
e have assumed you want to host your website in your home or home office using a topology similar to that in the diagram below. Before you do, you should at least weigh the merits of such a move.Alternatives To Home Web Hosting
It is easy to find virtual hosting companies on the Web which will offer to host a simple website for about $10 per month.
The steps are fairly straight forward:
• Sign up for the virtual hosting service. They will provide you with a login name and password, the IP address of your site plus the name of a private directory on a shared web server in which you’ll place your web pages.
• Register your domain name, such as www.my-site.com, with companies like Register.com, Verisign or RegisterFree.com. You must make sure your new domain name’s DNS records point to the DNS server of the virtual hosting company.
• Upload your web pages to your private virtual hosting directory.
• Test viewing your site using your IP address in your web browser. It takes about 3-4 days for DNS to propagate across the Web, so you’ll probably have to wait at least that long before you’ll be able to view your site using your domain, www.my-site.com.
The virtual hosting provider will also offer free backups of your site, technical support, a number of email addresses and an easy to use web based GUI to manage your settings. For an additional charge, many will also provide an e-commerce feature which will allow you to have a shopping cart and
customer loyalty programs.
Factors To Consider Before Hosting Yourself
Virtual hosting is the ideal solution for many small websites. There are a number of reasons why you may want to move your website to your home or small office.
Home Based Websites
Pros
o Cost: It is possible to host a website on most DSL connections. A website can be hosted on this data circuit for the only additional hardware cost of a network switch and a web server. You should be able to buy this equipment second hand for about $100. If your home already has DSL there would be no additional network connectivity costs. So for a savings of $10 per month the project should pay for itself in less than a year.
o New Skills: There is also the additional benefit of learning the new skills required to set up the site. Changes can be made with little delay.
o Availability: Reliable virtual hosting facilities may not be available in your country and/or you may not have access to the foreign currency to host your site abroad.
Cons
o Lost Services: You lose the convenience of many of the services such as backups, security audits, load balancing, DNS, redundant hardware, data base services and technical support offered by the virtual hosting company. For the home based website these are usually not big issues.
