Linux System Administration Recipes A Problem-Solution Approach

More documents

Recommendations

Info

CHAPTER 5 ■ WORKING WITH FILESYSTEMS■ Note You can’t convert backward from ext4 to ext3. It is possible (although complicated) to mount an ext3filesystem as ext4 without actually using any of the new data features, in which case you would still be able tomount the filesystem as ext3 as well. But it would be a bit pointless because you’d miss the ext4 features!XFSXFS is a 64-bit journaling filesystem created by Silicon Graphics. It’s available for nearly all mainstream<strong>Linux</strong> distros, although in general it’s not possible to use it for the boot partition, because grub doesn’talways handle it reliably. (However, you can create a small /boot partition as ext3 and then run the restof your filesystems as XFS.)Online defragmentation (that is, defragmentation while the filesystem is mounted) is available forXFS, although, like ext4, XFS uses delayed allocation and extents (a method of listing blocks that enablesthem to be given as a continuous list rather than named individually) to reduce fragmentation. To usethe xfs_fsr defragmentation tool, you’ll need to install the xfsdump package (Debian/Ubuntu).xfs_fsrJust using the command with no options will set it to spend 7,200 seconds (two hours) looping overand reorganizing the filesystems listed in /etc/mtab. To change this time to one hour (or substitute anyother seconds value), use this:xfs_fsr -t 3600Alternatively, you can set it to defragment a particular file:xfs_fsr /local/mybigfile.tar.gzYou can also use xfs_growfs to resize an XFS filesystem on the fly:xfs_growfs /filesystempath■ Note You will need space to grow the filesystem into! This is most often used with logical volume managementsetups. Or you can adapt recipe 5-5 to generate more partition space and then use xfs_growfs to extend thefilesystem.XFS is the fastest journaling filesystem in benchmarking tests and is reasonably low in CPU demand.Note, however, that an XFS filesystem can’t be shrunk once it’s created.134Download at WoweBook.Com
C H A P T E R 6■ ■ ■Securing Your <strong>System</strong>sSecurity concerns are a fact of life for any systems, especially once you connect your machines to theInternet at large. This chapter looks at various ways to use SSH and SSH keys, at setting and enforcingpassword policy on your system, at options to make sudo secure, and at increasing your protectionagainst other attacks from the outside world.6-1. Using and Limiting SSH KeysThe standard way of logging on with SSH is to just type your password when prompted. This does ofcourse work, but a better way of using SSH is via SSH keys.Using a key is more secure, because an attacker needs both the private key file and the passphraseto gain access to your account. You can also use it passphraseless (see recipe 6-3); this is less secure(relying on you keeping your private keyfile safe) but does enable unsupervised login for cronjobs and soon.One of the big advantages is that you can use ssh-add and ssh-agent to store your SSH keys for you(see recipe 6-2), thus meaning that you need to type your password only once. (See Chapter 2 forinformation on setting up Kerberos and getting single sign-in across your network, but SSH keys can stillbe useful for logging into other networks and for logging on as another user.)In particular, it’s useful to set up a key that will allow you to log in as root on all machines on yournetwork. Creating a key is straightforward. Enter the following in a terminal on your desktop machine.You don’t need to be root; indeed, you probably don’t want to be because it’s more useful to be able tolog in elsewhere as root while logged in as your default user on your own desktop.ssh-keygen -t rsa -f ~/.ssh/root_keyThis will generate an RSA key and save it in ~/.ssh/root_key, with the public part in~/.ssh/root_key.pub. Make sure you enter a good passphrase. Longer is better, with a mixture of letters,numbers, and punctuation.You can now simply cat the ~/.ssh/root_key.pub file into the /root/.ssh/authorized_keys2 or/root/.ssh/authorized_keys file on all your machines (you may have to create the /root/.ssh/directory).However, it’s a good idea to limit the scope of this key slightly so that in order to use it, you have tostart from your own desktop machine. To do this, first copy the contents of ~/.ssh/root_key.pub intotmpfile, and then add this to the start of the only line in tmpfile (note the comma at the end of the line!):135Download 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:
Page 101 and 102:
Page 103 and 104: 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 153: CHAPTER 5 ■ WORKING WITH FILESYST
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 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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?