Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 11 ■ TRACKING DOWN BUGS• Run top: Is there a process that’s chewing up all or a lot of the CPU? If so,depending on what it is, you may be able just to kill it.• Run ps -A: Are there lots of defunct processes? This can mean various things,but resolving whatever is happening may help you find what your bug is.• Run date: Check that the time is correct. Especially if you’re using Kerberos, it’simportant that the time on the local machine matches the time on the server towithin a few minutes.• Restart X: This is another in the “crude but often effective” box. Use/etc/init.d/gdm restart (if you use the GDM display manager; otherwise,replace as appropriate), or hit Ctrl-Alt-Backspace from the display.• Switch to a console (Ctrl-Alt-F1), and log in as root: Are there general login issues?This should show up if there are serious login problems.• Switch to a console (Ctrl-Alt-F1), and log in as yourself, a test user, or another user(or use su): Again, this may show up general login issues, in which case you maywant to take another look at whether your servers are up and responding.• Run iostat -dxk 5: This will give you a quick view of what the disk I/O is doing. -xgives an extended report, -d shows device utilization, -k shows KB per secondrather than bytes per second, and 5 refreshes every five seconds.11-3. Looking at diff Outputdiff is handy if you’re comparing config files from two separate machines. Copy the second file to thefirst machine (this example uses the /etc/hosts file):scp client1:/etc/hosts hosts-client1■ Note If you have SSH keys set up (see recipe 6-1), you can use this:diff /etc/hosts
CHAPTER 11 ■ TRACKING DOWN BUGS01 7c702 < 127.0.0.1 localhost03 ---04 > 127.0.0.1 localhost localhost.localdomain05 10a11,1206 >07 > 192.168.0.23 ldapserverLines 01–04 show the first change, and lines 05–07 show the second change. 7c7 means that in thisfirst change line 7 is being compared with line 7. In the first file (/etc/hosts) named on the commandline, line 7 is as shown in line 02 of the diff output (marked with ). Line 03 marks the division between thetwo files. (If multiple lines in a block were altered, you’d get more than one line at line 02 and line 04,and the dividing mark would be more useful.) So, in hosts-client1, 127.0.0.1 is also defined aslocalhost.localdomain, rather than just localhost.The second set of changes means that at line 10 the second file also adds lines 11 and 12. Lines 06and 07 of the diff output show those two added lines: an entry for the LDAP server.Another form of output is to use the -C option, which gives you a certain number of lines of contextfor each change. (Unfortunately, this isn’t compatible with the -y; option, which is described in a coupleof paragraphs.)> diff -C 1 /etc/hosts hosts-client1*** /etc/hosts 2009-02-02 21:45:58.000000000 +1300--- hosts-client1 2009-06-03 09:58:50.000000000 +1200****************** 6,8 ****##! 127.0.0.1 localhost255.255.255.255 broadcasthost--- 6,8 ----##! 127.0.0.1 localhost localhost.localdomain255.255.255.255 broadcasthost****************** 10 ****--- 10,12 ----fe80::1%lo0 localhost++ 192.168.0.23 ldapserverAs you can see, this form of output gives you a bit more information about the file and can be a littlemore readable than the default output. -C 1 gives you one line of context on each side of the change,with the change marked with ! for changed lines and + for added lines (- for removed lines, although thisis not shown here). You can specify as much context as you like; or -c gives a default three lines ofcontext.You can also use diff -y to show the files in two columns: the changes in the second file will bemarked with | for changes and > for added lines. If you do this, it’ll be easier to read if you also use the --suppress-common-lines option:diff -y --suppress-common-lines /etc/hosts hosts-client1217Download at WoweBook.Com
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Contents■About the Author .......
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■ CONTENTS3-7. Writing a Nagios P
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■ CONTENTS■Chapter 8: Using the
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■ CONTENTSAbout the Author■Juli
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■ CONTENTSAcknowledgmentsMany tha
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■ CONTENTSIntroductionThis book i
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■ INTRODUCTIONDownloading the Cod
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C H A P T E R 1■ ■ ■Saving Yo
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CHAPTER 1 ■ SAVING YOURSELF EFFOR
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C H A P T E R 2■ ■ ■Centraliz
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CHAPTER 2 ■ CENTRALIZING YOUR NET
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C H A P T E R 3■ ■ ■Monitorin
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CHAPTER 3 ■ MONITORING AND UPDATI
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C H A P T E R 4■ ■ ■Taking Ba
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CHAPTER 4 ■ TAKING BACKUPS AND MA
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C H A P T E R 5■ ■ ■Working w
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CHAPTER 5 ■ WORKING WITH FILESYST
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C H A P T E R 6■ ■ ■Securing
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CHAPTER 6 ■ SECURING YOUR SYSTEMS
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C H A P T E R 7■ ■ ■Working w
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CHAPTER 7 ■ WORKING WITH APACHEOn
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CHAPTER 7 ■ WORKING WITH APACHEdi
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CHAPTER 7 ■ WORKING WITH APACHE4.
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Page 191 and 192: C H A P T E R 8■ ■ ■Making Be
Page 193 and 194: CHAPTER 8 ■ USING THE COMMAND LIN
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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 233 and 234: C H A P T E R 11■ ■ ■Tracking
Page 235: CHAPTER 11 ■ TRACKING DOWN BUGSTh
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Page 251 and 252: C H A P T E R 12■ ■ ■Managing
Page 253 and 254: CHAPTER 12 ■ MANAGING TIME AND PE
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
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Linux System Administration Recipes A Problem-Solution Approach

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