Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFS■ Note This test user must also exist on the test machine either as a local user (in other words, in /etc/passwd;use *K* in the password field in /etc/shadow in this case) or in LDAP (see recipe 2-4) or your alternative directoryservice.Test the setup by logging on first with the console, then with a graphical logon (you may need torestart X first), and then via ssh. Once logged on to one Kerberized machine, you should be able to ssh toanother Kerberized machine without typing your password again. (However, this will work only if you’vedone all the client config described here for the second machine as well!)TroubleshootingHere are some things to check if it doesn’t work smoothly:• Check (using date) that the time on the KDC and the client machine are the sameor close. The default tolerance is five minutes. Daylight saving time can causetrouble!• Check that ping kerberos.example.com returns successfully and that there aren’tany other network problems.• Check that the host key has the correct number by executing the following on theclient:sudo klist -k /etc/krb5.keytabkinit krbadmkvno host/client.example.comIf the number of the host key for the client machine (host/client.example.com) given by klist is notthe same as the number given by kvno, you need to start up kadmin, remove the client principal from thekeytab (ktrem), delete it (delprinc), and then re-create and add it.2-3. Setting Up an LDAP ServerLightweight Directory Access Protocol (LDAP) is a way to define how a client and server interact witheach other. An LDAP directory is a directory whose server uses this protocol. Directories contain entries(structures that hold information about an object in the form of attributes) arranged in a tree.Schemas are used to define the syntax and structure for particular types of object and theirattributes. Plenty of standard schemas are available, and you can also create your own schemas or add toexisting ones. See recipe 2-12 for more information.28Download at WoweBook.Com
CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFSThese are the stages of an LDAP request:1. The client asks the server for a particular piece of information.2. The server runs the appropriate search (for example, finds the entry for agiven UID).3. The server returns the requested information (an entry or part of an entry) tothe client.LDAP can run either securely (using SSL on port 636 as ldaps:/// or using TLS over port 389 asldap:///) or otherwise (on port 389 as ldap:/// but without TLS). This recipe covers both, but it’s best touse secure LDAP unless you have a good reason to do otherwise.2-3a. OpenSSLOpenSSL enables you to run a secure LDAP server. For Debian/Ubuntu, run the following to install it:> sudo apt-get install libssl-dev openssl ca-certificates libssl0.9.8You have two options for getting a certificate:• Contact VeriSign or another certificate authority to sign your certificate. In thiscase, you’ll need only step 2 of the following process; follow your certificateauthority’s (CA’s) instructions about what to do with the request you produce.• Generate a self-signed certificate. If you’re going to use your certificate outside ofyour own network, it’s best to get a proper CA to sign it. If it’s just for local use,self-signing is fine (and free!).To generate a self-signed certificate, follow these steps (for a CA certificate, use step 2 without the -x509 option):1. First generate a certificate authority:> cd /etc/ssl> sudo /usr/lib/ssl/misc/CA.sh –newcaThe script requires various inputs. You’ll need a (secure) PEM passphrase(make sure you remember it!). The other important value is the common name(CN), which must match the FQDN of the certificate authority server (here, I’musing the LDAP server to be its own certificate authority, so the value isldapserver.example.com):Common Name (eg, YOUR name) []: ldap.example.comLeave the challenge password attribute empty.2. Create the certificate:openssl req -new -x509 -nodes -out newreq.pem -keyout newreq.pem -days 36529Download at WoweBook.Com
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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
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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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CHAPTER 7 ■ WORKING WITH APACHEOn
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CHAPTER 7 ■ WORKING WITH APACHE4.
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CHAPTER 7 ■ WORKING WITH APACHEAl
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C H A P T E R 8■ ■ ■Making Be
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CHAPTER 8 ■ USING THE COMMAND LIN
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CHAPTER 9 ■ WORKING WITH TEXT IN
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C H A P T E R 10■ ■ ■Things G
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CHAPTER 10 ■ THINGS GO IN, THINGS
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C H A P T E R 11■ ■ ■Tracking
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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CHAPTER 11 ■ TRACKING DOWN BUGS01
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CHAPTER 11 ■ TRACKING DOWN BUGS
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CHAPTER 11 ■ TRACKING DOWN BUGSTh
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CHAPTER 11 ■ TRACKING DOWN BUGSAn
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CHAPTER 11 ■ TRACKING DOWN BUGS#
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C H A P T E R 12■ ■ ■Managing
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CHAPTER 12 ■ MANAGING TIME AND PE
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APPENDIX■ ■ ■Perl TipsSee rec
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APPENDIX ■ PERL TIPS• Date::Par
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APPENDIX ■ PERL TIPSPerl Syntax N
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■ ■ ■Index■Symbols$CDPATH,
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■ INDEXenscript option (printing)
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■ INDEX■NNagiosadding hosts to,
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■ INDEXsyslogcentralized logging
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