Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFSAlternatively, you can start kpropd stand-alone from the command line with /usr/sbin/kpropd -S,in which case you will need to write an init script specifically for kpropd in order to start it at boot.Transfer the database from the master server:/usr/sbin/kdb5_util dump slave_transfer/usr/sbin/kprop -f slave_transfer server2.example.comRe-create the stash file (the file generated from the database password) on the slave server:kdb5_util -m stashEnter the password you used when creating the database on your master server.Start krb5-kdc on the slave server, and check the logs for errors. To confirm that it’s working, addthe slave entry, remove the master entry from /etc/krb5.conf on one of your clients, and check thatkdestroy; kinit works.TroubleshootingHere are some things to check if you get an error message:“Key table entry not found”:a. Check the logs. Is localhost being used instead of hostname?b. If so, edit /etc/hosts appropriately.“Key number mismatch”:a. Compare kvno host/server.example.com and klist -k /etc/krb5.keytab onboth servers.b. If they mismatch, you may need to destroy and re-create principals.c. In this instance, run kdestroy; kinit before trying again to clear cached keynumbers.“Cannot find KDC”:a. This may be a host resolve problem. Test this by replacing the name with theIP address in /etc/krb5.keytab.b. If this solves the problem, check /etc/hosts for the wrong localhost entries.The final step is to run kpropd regularly to propagate any changes in information from the master tothe slave. This is usually done with a two-line script (dump to file and propagate the file across), whichruns from /etc/crontab with the output directed to /dev/null.The downside to this is that while you don’t want to get the SUCCEEDED message e-mailed to youevery time it propagates successfully, you do want to know about it in the event of failure. This slightlyimproved script handles that:48Download at WoweBook.Com
CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFS#!/bin/sh# Script to run automatic Kerberos dump & transfer to slave serverDUMPFILE=/etc/krb5kdc/slave_dump_fileRESULT=/etc/krb5kdc/slave_dump_resultSLAVE=server2.example.comMAIL=sysadmin@example.com/usr/sbin/kdb5_util dump $DUMPFILE/usr/sbin/kprop -f $DUMPFILE $SLAVE > $RESULTif grep -vq SUCCEEDED $RESULT ; thenmail -s "Kerberos replication problem" $MAIL < $RESULTfiPut this in the /etc/cron.hourly directory. If you want to run it more often, add a line to /etc/crontab at whatever interval you prefer; you’ll probably want to keep the file in /etc/cron.d/ in this case.2-10. Adding a New User to LDAP with a ScriptLDIF is a format used to make changes to the LDAP database, and it’s perfectly possible to add, delete,and modify records just by writing LDIF files and using ldapadd, ldapmodify, and ldapdelete. In fact,sometimes that’s the best option. However, it’s useful to be able to script those interactions.perl-ldap is a very useful collection of Perl modules providing an OO interface to LDAP servers. Toinstall the Debian/Ubuntu package, run this:sudo apt-get install libnet-ldap-perlOr you can install it from CPAN by running this as root:perl -m CPAN -e "install perl-ldap"The following script will add a new user, with parameters taken from the command line. You wouldneed to authenticate as the LDAP admin user before running it in full (the parts that just search shouldwork as any user).Net::LDAP and Net::LDAPS are the modules that handle connecting and talking to the server.Net::LDAP deals with regular LDAP connections, and Net::LDAPS deals with LDAPS (secure) connections(although Net::LDAP also has options to force an ldaps:/// connection and to handle TLS with thestart_tls() method).The following code connects to an LDAP server, makes an anonymous bind, performs a search tolook for the new username (to see whether it already exists), adds the user, and takes the session down:01 #!/usr/bin/perl -w02 use strict;0304 # Use whichever module matches your server05 #use Net::LDAP;06 use Net::LDAPS;49Download 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
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 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 APACHE
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CHAPTER 7 ■ WORKING WITH APACHEAl
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CHAPTER 7 ■ WORKING WITH APACHE
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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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