Linux System Administration Recipes A Problem-Solution Approach

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CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFSIf slapd won’t start and there’s an “unstable alock” message in the logs (increase logging in/etc/ldap/slapd.conf to 1 to get better error messages), move /var/lib/ldap/alock out of the way andrestart. (/var/lib/ldap is where the various database files live. You shouldn’t need to interact with thisvery often.) Note that you may need to restart a couple of times and/or allow time for the restart to checkthe database, because the problem that this message indicates is that the database is or might becorrupt.2-7. Using LDAPThe basic LDAP commands are ldapadd, ldapmodify, and ldapdelete. Run kinit ldapadm before any ofthese to authenticate yourself if you’re using LDAP with Kerberos (replace ldapadm with your LDAPadmin user if it’s different). If using non-Kerberos authentication, use the -D and -W options:ldapadd -D cn=ldapadm,ou=admin,dc=example,dc=com -W-D specifies the distinguished name (DN) to use to bind to the server. This should be the DN of yourlocal admin or another user with appropriate privileges.-W will prompt you for the password, which is more secure than using the -w password option on thecommand line. The same options are valid for the other LDAP commands.■ Note See recipe 2-11 for how to use LDAP with Perl in a script.ldapsearchTo find a specific entry, use ldapsearch:ldapsearch "(uid=jkemp)"This uses a search filter in an LDAP-specific format. This example would search for an entry with theuid value exactly equal to jkemp. To search for a value that ends with kemp, you could use the following:ldapsearch "(uid=*kemp)"It’s important to get the double quotes and the brackets in the correct order! (The quotes go on theoutside.) You can also use AND and OR arguments, and other mathematical operators are supported. Thefollowing would search for a user who had a group ID greater than or equal to 1005 and a tcsh shell:ldapsearch "(&(gidNumber>=1005)(loginShell=*tcsh))"The AND is given by the & at the start of the filter (note the use of brackets). To exclude a particularuser from this, you can use !. The following would return all users with a group ID >= 1005 and a tcshshell, except for the user jkemp:ldapsearch "(&(gidNumber>=1005)(loginShell=*tcsh)(!uid=jkemp))"40Download at WoweBook.Com
CHAPTER 2 ■ CENTRALIZING YOUR NETWORK: KERBEROS, LDAP, AND NFSYou can string as many of these together as you like. You can also specify which attributes should bereturned. The following would return all users with a login shell of zsh or bash but would return onlytheir uid and cn:ldapsearch "(|(loginShell=*bash)(loginShell=*zsh))" uid cnThe | character at the start of the filter specifies OR. You can list as many attributes at the end of theline as you want to return.ldapaddTo add an entry from the command line, you use the command ldapadd. This takes an LDIF file as anargument:ldapadd -f newuser.ldifThe LDIF file specifies the entry or entries to add. You can also do this on the command line, butyou can edit a file if you make a mistake when typing and can edit and reuse it if you need to add othersimilar entries. The following is a sample newuser.ldif file, which would create a user entry and an entryfor the autofs map for their home directory (see recipe 2-13):dn: uid=jkemp,ou=People,dc=example,dc=comuid: jkempobjectClass: accountobjectClass: posixAccountobjectClass: topobjectClass: shadowAccountloginShell: /bin/bashuidNumber: 439gidNumber: 1005homeDirectory: /home/jkempgecos: Juliet Kempcn: Juliet Kempdn: cn=jkemp,ou=auto.home,dc=example,dc=comobjectClass: automountcn: jkempautomountInformation: -fstype=nfs,rw server1:/export/home/jkempautomountMapName: auto_homeUse a blank line to separate entries in the LDIF file, as shown here.ldapmodifyTo modify an existing entry, use ldapmodify. Like ldapadd, the best way to use this is with an LDIF file asan argument:ldapmodify -f modify_file41Download at WoweBook.Com
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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 41 and 42: C H A P T E R 2■ ■ ■Centraliz
Page 43 and 44: CHAPTER 2 ■ CENTRALIZING YOUR NET
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Page 83 and 84: C H A P T E R 3■ ■ ■Monitorin
Page 85 and 86: CHAPTER 3 ■ MONITORING AND UPDATI
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CHAPTER 3 ■ MONITORING AND UPDATI
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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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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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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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Linux System Administration Recipes A Problem-Solution Approach

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