Linux System Administration Recipes A Problem-Solution Approach

More documents

Recommendations

Info

CHAPTER 5 ■ WORKING WITH FILESYSTEMSIf you get a notification of a problem, it’s straightforward to remove the disk and rebuild the array.To check which disk has failed and what the problem is, use this:mdadm --query --detail /dev/md0Remove the faulty disk with the following:mdadm --remove /dev/md0 /dev/sda1/Run fsck on the disk:fsck /dev/sda1Once the problem is fixed, add the disk back into the array:mdadm --add /dev/md0 /dev/sda1/The array will automatically rebuild after the disk has been added back in.It’s usually worth trying fsck once to see whether this fixes the problem; disks do sometimes haveminor corruptions that aren’t indicative of serious hardware problems. If you have this problemrepeatedly and, in particular, if it’s the same disk repeatedly, it’s best to replace the disk altogether.■ Note To trigger a scan information e-mail, use mdadm --monitor --scan -1.5-7. Using rsnapshotSnapshot filesystems, which offer instant-availability backups from multiple time points, are a greatidea. But migrating to a new filesystem is a major deal. rsnapshot works on an ext3 filesystem; it usesrsync and hard links to create something that looks and works like multiple instant-availability fullbackups (as with a snapshot system) but that takes up the space of only one full backup plus incrementalchanges.That “full backup space” is of course still the gotcha—basically, you’ll need a spare disk. However,external disks are increasingly cheap, and rsnapshot can be used remotely with ssh. So, you could useone large central disk to keep snapshots of your most important data from multiple clients. (See recipe4-6 for another discussion of doing this without snapshots.)rsnapshot is relatively easy to configure. Install the rsnapshot Debian/Ubuntu package, and thencheck /etc/rsnapshot.conf for the minor edits needed, making sure to uncomment the interval lines.■ Note Directory names in /etc/rsnapshot.conf require a trailing slash, so it’s /local/, not /local. Also, youneed tabs (not spaces) between elements.130Download at WoweBook.Com
CHAPTER 5 ■ WORKING WITH FILESYSTEMSMost of the defaults should be fine. Make sure to uncomment the cmp_cp line because this (on a<strong>Linux</strong> system) enables rsnapshot to run more efficiently:cmd_cp/bin/cpSet the following lines to your own specification:snapshot_root /snapshotsinterval hourly 6interval daily 7interval weekly 4snapshot_root should be the mount point of your backup disk. The interval value sets how manyhours/days/months of snapshots are kept. (retain does the same thing in more recent versions ofrsnapshot, but the current Debian and Ubuntu files use interval.)■ Note If using removable backup media, uncomment this line:no_create_root 1This means that if the snapshot_root directory doesn’t exist, it won’t be created. So, if your removable mediaisn’t plugged in when an rsnapshot run is due, you won’t have the directory created on your existing disk andbacked up into, thus potentially causing problems with space.Set up your backup directories in this form:backup/local/ localdata/This will back up the /local/ directory to /snapshots/hourly.0/localdata/local/. Daily snapshotswill go to /snapshots/daily.0/localdata/local/, and so on. The next time a snapshot is run, this willmove to /snapshots/hourly.1/localdata/local/, although in fact hard links are used extensively tominimize space usage.Add another line for each directory you want to back up.To run an hourly backup from the command line (to test), use this:rsnapshot hourlyThe first run may take a while (as always with a first run of rsync). Subsequent runs will be muchfaster because the files are updated from the snapshot.Once you’ve confirmed that it’s working correctly, you probably want to set up a cronjob to run itautomatically. The package automatically installs an /etc/cron.d/rsnapshot file. You can uncomment(and edit if need be) the relevant lines in this to run it automatically, or you can add these lines to your/etc/crontab:131Download at WoweBook.Com
Page 2:
Download at WoweBook.Com
Page 5 and 6:
Download at WoweBook.Comiii
Page 7 and 8:
Contents■About the Author .......
Page 9 and 10:
■ CONTENTS3-7. Writing a Nagios P
Page 11 and 12:
■ CONTENTS■Chapter 8: Using the
Page 13 and 14:
■ CONTENTSAbout the Author■Juli
Page 15 and 16:
■ CONTENTSAcknowledgmentsMany tha
Page 17 and 18:
■ CONTENTSIntroductionThis book i
Page 19 and 20:
■ INTRODUCTIONDownloading the Cod
Page 21 and 22:
C H A P T E R 1■ ■ ■Saving Yo
Page 23 and 24:
CHAPTER 1 ■ SAVING YOURSELF EFFOR
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
C H A P T E R 2■ ■ ■Centraliz
Page 43 and 44:
CHAPTER 2 ■ CENTRALIZING YOUR NET
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
C H A P T E R 3■ ■ ■Monitorin
Page 85 and 86:
CHAPTER 3 ■ MONITORING AND UPDATI
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100: CHAPTER 3 ■ MONITORING AND UPDATI
Page 115 and 116: C H A P T E R 4■ ■ ■Taking Ba
Page 117 and 118: CHAPTER 4 ■ TAKING BACKUPS AND MA
Page 139 and 140: C H A P T E R 5■ ■ ■Working w
Page 141 and 142: CHAPTER 5 ■ WORKING WITH FILESYST
Page 149: CHAPTER 5 ■ WORKING WITH FILESYST
Page 155 and 156: C H A P T E R 6■ ■ ■Securing
Page 157 and 158: CHAPTER 6 ■ SECURING YOUR SYSTEMS
Page 177 and 178: C H A P T E R 7■ ■ ■Working w
Page 179 and 180: CHAPTER 7 ■ WORKING WITH APACHEOn
Page 181 and 182: CHAPTER 7 ■ WORKING WITH APACHEdi
Page 183 and 184: CHAPTER 7 ■ WORKING WITH APACHE4.
Page 185 and 186: CHAPTER 7 ■ WORKING WITH APACHE
Page 187 and 188: CHAPTER 7 ■ WORKING WITH APACHEAl
Page 189 and 190: CHAPTER 7 ■ WORKING WITH APACHE
Page 191 and 192: C H A P T E R 8■ ■ ■Making Be
Page 193 and 194: CHAPTER 8 ■ USING THE COMMAND LIN
Page 201 and 202:
CHAPTER 8 ■ USING THE COMMAND LIN
Page 203 and 204:
CHAPTER 8 ■ USING THE COMMAND LIN
Page 205 and 206:
C H A P T E R 9■ ■ ■Working w
Page 207 and 208:
CHAPTER 9 ■ WORKING WITH TEXT IN
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
C H A P T E R 10■ ■ ■Things G
Page 225 and 226:
CHAPTER 10 ■ THINGS GO IN, THINGS
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
C H A P T E R 11■ ■ ■Tracking
Page 235 and 236:
CHAPTER 11 ■ TRACKING DOWN BUGSTh
Page 237 and 238:
CHAPTER 11 ■ TRACKING DOWN BUGS01
Page 239 and 240:
CHAPTER 11 ■ TRACKING DOWN BUGS
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
CHAPTER 11 ■ TRACKING DOWN BUGSTh
Page 247 and 248:
CHAPTER 11 ■ TRACKING DOWN BUGSAn
Page 249 and 250:
CHAPTER 11 ■ TRACKING DOWN BUGS#
Page 251 and 252:
C H A P T E R 12■ ■ ■Managing
Page 253 and 254:
CHAPTER 12 ■ MANAGING TIME AND PE
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
APPENDIX■ ■ ■Perl TipsSee rec
Page 269 and 270:
APPENDIX ■ PERL TIPS• Date::Par
Page 271 and 272:
APPENDIX ■ PERL TIPSPerl Syntax N
Page 273 and 274:
■ ■ ■Index■Symbols$CDPATH,
Page 275 and 276:
■ INDEXenscript option (printing)
Page 277 and 278:
■ INDEX■NNagiosadding hosts to,
Page 279 and 280:
■ INDEXsyslogcentralized logging
Page 281 and 282:
Download at WoweBook.Com
show all

Linux System Administration Recipes A Problem-Solution Approach

Create successful ePaper yourself

Delete template?

Save as template?