Red Hat ENTERPRISE LINUX 5 - VIRTUAL SERVER... Quick reference guide

Red Hat Enterprise Linux 5
Deployment Guide
Deployment, configuration and
administration of Red Hat Enterprise Linux 5
Deployment_Guide

Deployment Guide
Red Hat Enterprise Linux 5 Deployment Guide
Deployment, configuration and administration of Red Hat
Enterprise Linux 5
Edition 4
Copyright © 2007, 2008, 2009, 2010 Red Hat Inc..
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The Deployment Guide documents relevant information reegarding the deployment, configuration and
administration of Red Hat Enterprise Linux 5.

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Introduction xxiii
1. Document Conventions ................................................................................................ xxiii
2. Send in Your Feedback ............................................................................................... xxvi
I. File Systems 1
1. File System Structure 3
1.1. Why Share a Common Structure? ......................................................................... 3
1.2. Overview of File System Hierarchy Standard (FHS) ................................................ 3
1.2.1. FHS Organization ...................................................................................... 3
1.3. Special File Locations Under Red Hat Enterprise Linux .......................................... 8
2. The ext3 File System 11
2.1. Features of ext3 ................................................................................................. 11
2.2. Creating an ext3 File System .............................................................................. 11
2.3. Converting to an ext3 File System ....................................................................... 12
2.4. Reverting to an ext2 File System ........................................................................ 12
3. The proc File System 15
3.1. A Virtual File System .......................................................................................... 15
3.1.1. Viewing Virtual Files ................................................................................ 15
3.1.2. Changing Virtual Files .............................................................................. 16
3.2. Top-level Files within the proc File System ......................................................... 16
3.2.1. /proc/apm ............................................................................................. 16
3.2.2. /proc/buddyinfo ................................................................................. 17
3.2.3. /proc/cmdline ..................................................................................... 17
3.2.4. /proc/cpuinfo ..................................................................................... 18
3.2.5. /proc/crypto ....................................................................................... 19
3.2.6. /proc/devices ..................................................................................... 19
3.2.7. /proc/dma ............................................................................................. 20
3.2.8. /proc/execdomains ............................................................................. 20
3.2.9. /proc/fb ............................................................................................... 21
3.2.10. /proc/filesystems ........................................................................... 21
3.2.11. /proc/interrupts ............................................................................. 21
3.2.12. /proc/iomem ....................................................................................... 22
3.2.13. /proc/ioports ................................................................................... 23
3.2.14. /proc/kcore ....................................................................................... 23
3.2.15. /proc/kmsg ......................................................................................... 23
3.2.16. /proc/loadavg ................................................................................... 24
3.2.17. /proc/locks ....................................................................................... 24
3.2.18. /proc/mdstat ..................................................................................... 24
3.2.19. /proc/meminfo ................................................................................... 25
3.2.20. /proc/misc ......................................................................................... 26
3.2.21. /proc/modules ................................................................................... 27
3.2.22. /proc/mounts ..................................................................................... 27
3.2.23. /proc/mtrr ......................................................................................... 28
3.2.24. /proc/partitions ............................................................................. 28
3.2.25. /proc/pci ........................................................................................... 29
3.2.26. /proc/slabinfo ................................................................................. 29
3.2.27. /proc/stat ......................................................................................... 30
3.2.28. /proc/swaps ....................................................................................... 31
3.2.29. /proc/sysrq-trigger ....................................................................... 32

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3.2.30. /proc/uptime ..................................................................................... 32
3.2.31. /proc/version ................................................................................... 32
3.3. Directories within /proc/ ................................................................................... 32
3.3.1. Process Directories .................................................................................. 32
3.3.2. /proc/bus/ ........................................................................................... 34
3.3.3. /proc/driver/ ..................................................................................... 35
3.3.4. /proc/fs ............................................................................................... 36
3.3.5. /proc/ide/ ........................................................................................... 36
3.3.6. /proc/irq/ ........................................................................................... 37
3.3.7. /proc/net/ ........................................................................................... 37
3.3.8. /proc/scsi/ ......................................................................................... 38
3.3.9. /proc/sys/ ........................................................................................... 40
3.3.10. /proc/sysvipc/ ................................................................................. 51
3.3.11. /proc/tty/ ......................................................................................... 51
3.4. Using the sysctl Command .............................................................................. 51
3.5. Additional Resources .......................................................................................... 52
3.5.1. Installed Documentation ........................................................................... 52
3.5.2. Useful Websites ...................................................................................... 52
4. Redundant Array of Independent Disks (RAID) 53
4.1. What is RAID? ................................................................................................... 53
4.2. Who Should Use RAID? ..................................................................................... 53
4.3. Hardware RAID versus Software RAID ................................................................ 53
4.3.1. Hardware RAID ....................................................................................... 53
4.3.2. Software RAID ........................................................................................ 54
4.4. RAID Levels and Linear Support ......................................................................... 54
4.5. Configuring Software RAID ................................................................................. 55
4.5.1. Creating the RAID Partitions .................................................................... 56
4.5.2. Creating the RAID Devices and Mount Points ............................................ 59
5. Swap Space 65
5.1. What is Swap Space? ........................................................................................ 65
5.2. Adding Swap Space ........................................................................................... 65
5.2.1. Extending Swap on an LVM2 Logical Volume ............................................ 66
5.2.2. Creating an LVM2 Logical Volume for Swap .............................................. 66
5.2.3. Creating a Swap File ............................................................................... 67
5.3. Removing Swap Space ...................................................................................... 67
5.3.1. Reducing Swap on an LVM2 Logical Volume ............................................ 68
5.3.2. Removing an LVM2 Logical Volume for Swap ........................................... 68
5.3.3. Removing a Swap File ............................................................................. 69
5.4. Moving Swap Space ........................................................................................... 69
6. Managing Disk Storage 71
6.1. Standard Partitions using parted ....................................................................... 71
6.1.1. Viewing the Partition Table ....................................................................... 72
6.1.2. Creating a Partition .................................................................................. 73
6.1.3. Removing a Partition ............................................................................... 75
6.1.4. Resizing a Partition .................................................................................. 76
6.2. LVM Partition Management ................................................................................. 77
7. Implementing Disk Quotas 79
7.1. Configuring Disk Quotas ..................................................................................... 79
7.1.1. Enabling Quotas ...................................................................................... 79

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7.1.2. Remounting the File Systems ................................................................... 80
7.1.3. Creating the Quota Database Files ........................................................... 80
7.1.4. Assigning Quotas per User ...................................................................... 81
7.1.5. Assigning Quotas per Group .................................................................... 82
7.1.6. Setting the Grace Period for Soft Limits .................................................... 82
7.2. Managing Disk Quotas ....................................................................................... 82
7.2.1. Enabling and Disabling ............................................................................ 83
7.2.2. Reporting on Disk Quotas ........................................................................ 83
7.2.3. Keeping Quotas Accurate ......................................................................... 84
7.3. Additional Resources .......................................................................................... 84
7.3.1. Installed Documentation ........................................................................... 84
7.3.2. Related Books ......................................................................................... 84
8. Access Control Lists 85
8.1. Mounting File Systems ....................................................................................... 85
8.1.1. NFS ........................................................................................................ 85
8.2. Setting Access ACLs .......................................................................................... 85
8.3. Setting Default ACLs .......................................................................................... 86
8.4. Retrieving ACLs ................................................................................................. 87
8.5. Archiving File Systems With ACLs ....................................................................... 87
8.6. Compatibility with Older Systems ........................................................................ 88
8.7. Additional Resources .......................................................................................... 88
8.7.1. Installed Documentation ........................................................................... 88
8.7.2. Useful Websites ...................................................................................... 89
9. LVM (Logical Volume Manager) 91
9.1. What is LVM? .................................................................................................... 91
9.1.1. What is LVM2? ........................................................................................ 92
9.2. LVM Configuration .............................................................................................. 92
9.3. Automatic Partitioning ......................................................................................... 93
9.4. Manual LVM Partitioning ..................................................................................... 94
9.4.1. Creating the /boot/ Partition .................................................................. 94
9.4.2. Creating the LVM Physical Volumes ......................................................... 97
9.4.3. Creating the LVM Volume Groups ............................................................ 99
9.4.4. Creating the LVM Logical Volumes ......................................................... 100
9.5. Using the LVM utility system-config-lvm ...................................................... 103
9.5.1. Utilizing uninitialized entities ................................................................... 106
9.5.2. Adding Unallocated Volumes to a volume group ...................................... 107
9.5.3. Migrating extents ................................................................................... 109
9.5.4. Adding a new hard disk using LVM ......................................................... 111
9.5.5. Adding a new volume group ................................................................... 112
9.5.6. Extending a volume group ...................................................................... 114
9.5.7. Editing a Logical Volume ........................................................................ 115
9.6. Additional Resources ........................................................................................ 117
9.6.1. Installed Documentation ......................................................................... 117
9.6.2. Useful Websites ..................................................................................... 117
II. Package Management 119
10. Package Management with RPM 121
10.1. RPM Design Goals ......................................................................................... 121
10.2. Using RPM ..................................................................................................... 122

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10.2.1. Finding RPM Packages ........................................................................ 122
10.2.2. Installing .............................................................................................. 122
10.2.3. Uninstalling .......................................................................................... 124
10.2.4. Upgrading ............................................................................................ 125
10.2.5. Freshening .......................................................................................... 126
10.2.6. Querying .............................................................................................. 126
10.2.7. Verifying .............................................................................................. 127
10.3. Checking a Package's Signature ..................................................................... 128
10.3.1. Importing Keys ..................................................................................... 128
10.3.2. Verifying Signature of Packages ........................................................... 129
10.4. Practical and Common Examples of RPM Usage .............................................. 129
10.5. Additional Resources ...................................................................................... 131
10.5.1. Installed Documentation ....................................................................... 131
10.5.2. Useful Websites ................................................................................... 131
10.5.3. Related Books ..................................................................................... 131
11. Package Management Tool 133
11.1. Listing and Analyzing Packages ...................................................................... 133
11.2. Installing and Removing Packages .................................................................. 134
12. YUM (Yellowdog Updater Modified) 141
12.1. Setting Up a yum Repository ........................................................................... 141
12.2. yum Commands .............................................................................................. 141
12.3. yum Options ................................................................................................... 142
12.4. Configuring yum .............................................................................................. 142
12.4.1. [main] Options .................................................................................. 143
12.4.2. [repository] Options ....................................................................... 144
12.5. Useful yum Variables ...................................................................................... 145
13. Red Hat Network 147
III. Network-Related Configuration 151
14. Network Interfaces 153
14.1. Network Configuration Files ............................................................................. 153
14.2. Interface Configuration Files ............................................................................ 154
14.2.1. Ethernet Interfaces ............................................................................... 154
14.2.2. IPsec Interfaces ................................................................................... 157
14.2.3. Channel Bonding Interfaces .................................................................. 158
14.2.4. Alias and Clone Files ........................................................................... 159
14.2.5. Dialup Interfaces .................................................................................. 160
14.2.6. Other Interfaces ................................................................................... 161
14.3. Interface Control Scripts .................................................................................. 162
14.4. Configuring Static Routes ................................................................................ 164
14.5. Network Function Files .................................................................................... 166
14.6. Additional Resources ...................................................................................... 166
14.6.1. Installed Documentation ....................................................................... 166
15. Network Configuration 167
15.1. Overview ........................................................................................................ 168
15.2. Establishing an Ethernet Connection ................................................................ 169
15.3. Establishing an ISDN Connection .................................................................... 172
15.4. Establishing a Modem Connection ................................................................... 173

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15.5. Establishing an xDSL Connection .................................................................... 175
15.6. Establishing a Token Ring Connection ............................................................. 181
15.7. Establishing a Wireless Connection ................................................................. 183
15.8. Managing DNS Settings .................................................................................. 186
15.9. Managing Hosts .............................................................................................. 187
15.10. Working with Profiles .................................................................................... 189
15.11. Device Aliases .............................................................................................. 192
15.12. Saving and Restoring the Network Configuration ............................................. 194
16. Controlling Access to Services 195
16.1. Runlevels ....................................................................................................... 196
16.2. TCP Wrappers ................................................................................................ 196
16.2.1. xinetd ............................................................................................... 196
16.3. Services Configuration Tool ......................................................................... 197
16.4. ntsysv ........................................................................................................... 199
16.5. chkconfig .................................................................................................... 201
16.6. Additional Resources ...................................................................................... 201
16.6.1. Installed Documentation ....................................................................... 201
16.6.2. Useful Websites ................................................................................... 201
17. Berkeley Internet Name Domain (BIND) 203
17.1. Introduction to DNS ........................................................................................ 203
17.1.1. Nameserver Zones ............................................................................... 203
17.1.2. Nameserver Types ............................................................................... 204
17.1.3. BIND as a Nameserver ........................................................................ 204
17.2. /etc/named.conf ........................................................................................ 205
17.2.1. Common Statement Types ................................................................... 205
17.2.2. Other Statement Types ........................................................................ 210
17.2.3. Comment Tags .................................................................................... 211
17.3. Zone Files ...................................................................................................... 212
17.3.1. Zone File Directives ............................................................................. 212
17.3.2. Zone File Resource Records ................................................................ 213
17.3.3. Example Zone File ............................................................................... 216
17.3.4. Reverse Name Resolution Zone Files ................................................... 217
17.4. Using rndc .................................................................................................... 218
17.4.1. Configuring /etc/named.conf ........................................................... 218
17.4.2. Configuring /etc/rndc.conf ............................................................. 219
17.4.3. Command Line Options ........................................................................ 220
17.5. Advanced Features of BIND ............................................................................ 220
17.5.1. DNS Protocol Enhancements ................................................................ 221
17.5.2. Multiple Views ...................................................................................... 221
17.5.3. Security ............................................................................................... 221
17.5.4. IP version 6 ......................................................................................... 222
17.6. Common Mistakes to Avoid ............................................................................. 222
17.7. Additional Resources ...................................................................................... 223
17.7.1. Installed Documentation ....................................................................... 223
17.7.2. Useful Websites ................................................................................... 224
17.7.3. Related Books ..................................................................................... 224
18. OpenSSH 225
18.1. Features of SSH ............................................................................................. 225
18.1.1. Why Use SSH? ................................................................................... 225
18.2. SSH Protocol Versions .................................................................................... 226

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18.3. Event Sequence of an SSH Connection ........................................................... 226
18.3.1. Transport Layer ................................................................................... 226
18.3.2. Authentication ...................................................................................... 227
18.3.3. Channels ............................................................................................. 228
18.4. Configuring an OpenSSH Server ..................................................................... 228
18.4.1. Requiring SSH for Remote Connections ................................................ 229
18.5. OpenSSH Configuration Files .......................................................................... 229
18.6. Configuring an OpenSSH Client ...................................................................... 230
18.6.1. Using the ssh Command ..................................................................... 230
18.6.2. Using the scp Command ..................................................................... 231
18.6.3. Using the sftp Command ................................................................... 232
18.7. More Than a Secure Shell .............................................................................. 232
18.7.1. X11 Forwarding ................................................................................... 232
18.7.2. Port Forwarding ................................................................................... 233
18.7.3. Generating Key Pairs ........................................................................... 234
18.8. Additional Resources ...................................................................................... 237
18.8.1. Installed Documentation ....................................................................... 237
18.8.2. Useful Websites ................................................................................... 237
19. Network File System (NFS) 239
19.1. How It Works ................................................................................................. 239
19.1.1. Required Services ................................................................................ 240
19.2. NFS Client Configuration ................................................................................. 241
19.2.1. Mounting NFS File Systems using /etc/fstab .................................... 241
19.3. autofs .......................................................................................................... 242
19.3.1. What's new in autofs version 5? ......................................................... 242
19.3.2. autofs Configuration .......................................................................... 243
19.3.3. autofs Common Tasks ....................................................................... 244
19.4. Common NFS Mount Options .......................................................................... 248
19.5. Starting and Stopping NFS .............................................................................. 249
19.6. NFS Server Configuration ............................................................................... 250
19.6.1. Exporting or Sharing NFS File Systems ................................................. 251
19.6.2. Command Line Configuration ................................................................ 255
19.6.3. Running NFS Behind a Firewall ............................................................ 256
19.6.4. Hostname Formats ............................................................................... 256
19.7. The /etc/exports Configuration File ............................................................ 256
19.7.1. The exportfs Command .................................................................... 258
19.8. Securing NFS ................................................................................................. 260
19.8.1. Host Access ........................................................................................ 260
19.8.2. File Permissions .................................................................................. 261
19.9. NFS and portmap ......................................................................................... 262
19.9.1. Troubleshooting NFS and portmap ...................................................... 262
19.10. Using NFS over TCP .................................................................................... 263
19.11. Additional Resources .................................................................................... 264
19.11.1. Installed Documentation ...................................................................... 264
19.11.2. Useful Websites ................................................................................. 264
19.11.3. Related Books ................................................................................... 264
20. Samba 265
20.1. Introduction to Samba ..................................................................................... 265
20.1.1. Samba Features .................................................................................. 265
20.2. Samba Daemons and Related Services ........................................................... 265

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20.2.1. Samba Daemons ................................................................................. 266
20.3. Connecting to a Samba Share ......................................................................... 266
20.3.1. Command Line .................................................................................... 268
20.3.2. Mounting the Share .............................................................................. 269
20.4. Configuring a Samba Server ........................................................................... 269
20.4.1. Graphical Configuration ........................................................................ 269
20.4.2. Command Line Configuration ................................................................ 274
20.4.3. Encrypted Passwords ........................................................................... 274
20.5. Starting and Stopping Samba .......................................................................... 274
20.6. Samba Server Types and the smb.conf File ................................................... 275
20.6.1. Stand-alone Server .............................................................................. 276
20.6.2. Domain Member Server ....................................................................... 278
20.6.3. Domain Controller ................................................................................ 280
20.7. Samba Security Modes ................................................................................... 281
20.7.1. User-Level Security .............................................................................. 281
20.7.2. Share-Level Security ............................................................................ 283
20.8. Samba Account Information Databases ............................................................ 283
20.9. Samba Network Browsing ............................................................................... 284
20.9.1. Domain Browsing ................................................................................. 284
20.9.2. WINS (Windows Internetworking Name Server) ...................................... 285
20.10. Samba with CUPS Printing Support ............................................................... 285
20.10.1. Simple smb.conf Settings ................................................................. 285
20.11. Samba Distribution Programs ........................................................................ 286
20.12. Additional Resources .................................................................................... 290
20.12.1. Installed Documentation ...................................................................... 290
20.12.2. Related Books ................................................................................... 290
20.12.3. Useful Websites ................................................................................. 291
21. Dynamic Host Configuration Protocol (DHCP) 293
21.1. Why Use DHCP? ............................................................................................ 293
21.2. Configuring a DHCP Server ............................................................................ 293
21.2.1. Configuration File ................................................................................. 293
21.2.2. Lease Database ................................................................................... 297
21.2.3. Starting and Stopping the Server .......................................................... 297
21.2.4. DHCP Relay Agent .............................................................................. 298
21.3. Configuring a DHCP Client .............................................................................. 298
21.4. Configuring a Multihomed DHCP Server .......................................................... 299
21.4.1. Host Configuration ............................................................................... 301
21.5. Additional Resources ...................................................................................... 303
21.5.1. Installed Documentation ....................................................................... 303
22. Apache HTTP Server 305
22.1. Apache HTTP Server 2.2 ................................................................................ 305
22.1.1. Features of Apache HTTP Server 2.2 .................................................... 305
22.2. Migrating Apache HTTP Server Configuration Files ........................................... 306
22.2.1. Migrating Apache HTTP Server 2.0 Configuration Files ........................... 306
22.2.2. Migrating Apache HTTP Server 1.3 Configuration Files to 2.0 .................. 306
22.3. Starting and Stopping httpd .......................................................................... 316
22.4. Apache HTTP Server Configuration ................................................................. 317
22.4.1. Basic Settings ...................................................................................... 318
22.4.2. Default Settings ................................................................................... 320
22.5. Configuration Directives in httpd.conf .......................................................... 331

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22.5.1. General Configuration Tips ................................................................... 331
22.5.2. Configuration Directives for SSL ........................................................... 345
22.5.3. MPM Specific Server-Pool Directives ..................................................... 345
22.6. Adding Modules .............................................................................................. 347
22.7. Virtual Hosts ................................................................................................... 347
22.7.1. Setting Up Virtual Hosts ....................................................................... 347
22.8. Apache HTTP Secure Server Configuration ...................................................... 348
22.8.1. An Overview of Security-Related Packages ........................................... 349
22.8.2. An Overview of Certificates and Security ............................................... 349
22.8.3. Using Pre-Existing Keys and Certificates ............................................... 350
22.8.4. Types of Certificates ............................................................................ 350
22.8.5. Generating a Key ................................................................................. 352
22.8.6. How to configure the server to use the new key ..................................... 360
22.9. Additional Resources ...................................................................................... 360
22.9.1. Useful Websites ................................................................................... 361
23. FTP 363
23.1. The File Transfer Protocol ............................................................................... 363
23.1.1. Multiple Ports, Multiple Modes .............................................................. 363
23.2. FTP Servers ................................................................................................... 363
23.2.1. vsftpd ............................................................................................... 364
23.3. Files Installed with vsftpd ............................................................................. 364
23.4. Starting and Stopping vsftpd ........................................................................ 365
23.4.1. Starting Multiple Copies of vsftpd ....................................................... 366
23.5. vsftpd Configuration Options ......................................................................... 367
23.5.1. Daemon Options .................................................................................. 367
23.5.2. Log In Options and Access Controls ..................................................... 368
23.5.3. Anonymous User Options ..................................................................... 369
23.5.4. Local User Options .............................................................................. 370
23.5.5. Directory Options ................................................................................. 371
23.5.6. File Transfer Options ............................................................................ 372
23.5.7. Logging Options ................................................................................... 372
23.5.8. Network Options .................................................................................. 373
23.6. Additional Resources ...................................................................................... 375
23.6.1. Installed Documentation ....................................................................... 376
23.6.2. Useful Websites ................................................................................... 376
24. Email 377
24.1. Email Protocols .............................................................................................. 377
24.1.1. Mail Transport Protocols ....................................................................... 377
24.1.2. Mail Access Protocols .......................................................................... 378
24.2. Email Program Classifications ......................................................................... 380
24.2.1. Mail Transport Agent ............................................................................ 380
24.2.2. Mail Delivery Agent .............................................................................. 380
24.2.3. Mail User Agent ................................................................................... 380
24.3. Mail Transport Agents ..................................................................................... 381
24.3.1. Sendmail ............................................................................................. 381
24.3.2. Postfix ................................................................................................. 385
24.3.3. Fetchmail ............................................................................................. 387
24.4. Mail Transport Agent (MTA) Configuration ........................................................ 390
24.5. Mail Delivery Agents ....................................................................................... 392
24.5.1. Procmail Configuration ......................................................................... 392