CIT 470: Advanced Network and System Administration Slide #1
CIT 470: Advanced Network and System Administration
Directories
Topics
1. Directories
2. LDAP Structure
3. LDIF
4. Distinguished Names
5. Replication
6. OpenLDAP Configuration
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What is a Directory?
Directory: A collection of information that is primarily searched and read, rarely modified.
Directory Service: Provides access to directory information.
Directory Server: Application that provides a directory service.
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Directories vs. Databases
Directories are optimized for reading.– Databases balanced for read and write.
Directories are tree-structured.– Databases typically have relational structure.
Directories are usually replicated.– Databases can be replicated too.
Both are extensible data storage systems.
Both have advanced search capabilities.
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System Administration Directories
Types of directory data– Accounts– Mail aliases and lists (address book)– Cryptographic keys– IP addresses– Hostnames– Printers
Common directory services– DNS, LDAP, NIS
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Advantages of Directories
Make administration easier.– Change data only once: people, accounts, hosts.
Unify access to network resources.– Single sign on.– Single place for users to search (address book)
Improve data management– Improve consistency (one location vs many)– Secure data through only one server.
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NIS: Network Information Service
Originally called Sun Yellow Pages– Clients run ypbind.– Servers run ypserv.– Data stored under /var/yp on server.
Server shares NIS maps with clients– Each UNIX file may provide multiple NIS maps.– NIS maps map keys like UID, username to data.– passwd: passwd.byname, passwd.byuid
Slave servers replicate master server content.Easy to use, but insecure, difficult to extend.
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LDAP
Lightweight Directory Access Protocol– Lightweight compared to X.500 directories.– Directory, not a database, service.– Access Protocol, not a directory itself.
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LDAP Clients and ServersLDAP Clients
– Standalone directory browsers.– Embedded clients (mail clients, logins, etc.)– Cfg /etc/nsswitch.conf on UNIX to use LDAP.
Common LDAP servers
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LDAP Structure
An LDAP directory is made of entries.– Entries may be employee records, hosts, etc.
Each entries consists of attributes.– Attributes can be names, phone numbers, etc.– objectClass attribute identifies entry type.
Each attribute is a type / value pair.– Type is a label for the information stored (name)– Value is value for the attribute in this entry.– Attributes can be multi-valued.
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Tree-structure of LDAP Directories
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LDAP SchemasSchemas specify allowed objectClasses and attributes.
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LDIF
LDAP Interchange Format.– Standard text format for storing LDAP configuration
data and directory contents.
LDIF Files– Collection of entries separated by blank lines.– Mapping of attribute names to values.
Uses– Import new data into directory.– Export directory to LDIF files for backups.
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LDIF Output Example
LDIF Backups and Restores
Backing up an LDAP directoryslapcat > backup.ldif
OR to do a daily backup use date in name
slapcat > backup-`date +%F`.ldif
Restoring an LDAP directoryservice ldap stop
rm -rf /var/lib/ldap/*
slapadd < backup.ldif
service ldap start
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Distinguished Names
Distinguished Names (DNs)– Uniquely identify an LDAP entry.– Provides path from LDAP root to the named entry.– Similar to an absolute pathname.– dn:cn=Jeff Foo,ou=Sales,dc=plainjoe,dc=org
Relative DNs (RDNs)– Any unique attribute pair in directory’s container.– ex: cn=Jeff Foo OR username=fooj– Similar to a relative pathname.– Except may have multiple components.– cn=Jane Smith+ou=Sales– cn=Jane Smith+ou=Engineering
(R)DN Example #1
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(R)DN Example #2
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ldapsearch
Options-LLL removes comments and LDAP version info.
-b base supplies base DN (uses ldap.conf if no -b.)
-x uses simple authentication instead of SASL.
-H ldap://your.server.edu accesses that server.
If -H not specified, uses ldap.conf to find server.
Search for all elementsldapsearch -LLL -x -b "dc=gkar,dc=nku,dc=edu"
"(objectclass=*)"
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ldapsearch -LLL -x "(DN)"> ldapsearch -LLL -x "(uid=fooj)"
dn: uid=fooj,ou=People,dc=gkar,dc=nku,dc=edu
objectClass: top
objectClass: account
objectClass: posixAccount
objectClass: shadowAccount
uid: fooj
uidNumber: 10101
cn: fooj
homeDirectory: /home/c/fooj
loginShell: /bin/bash
gidNumber: 10101
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ldapsearch -LLL -x "(DN)"> ldapsearch -LLL -x "(uidNumber=10101)"
dn: uid=fooj,ou=People,dc=gkar,dc=nku,dc=edu
objectClass: top
objectClass: account
objectClass: posixAccount
objectClass: shadowAccount
uid: fooj
uidNumber: 10101
cn: fooj
homeDirectory: /home/c/fooj
loginShell: /bin/bash
gidNumber: 10101
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Multiple Record Matches> ldapsearch -LLL -x "(loginShell=/bin/bash)"
dn: uid=fooj,ou=People,dc=gkar,dc=nku,dc=edu
objectClass: top
objectClass: account
objectClass: posixAccount
objectClass: shadowAccount
uid: fooj
uidNumber: 10101
cn: fooj
homeDirectory: /home/b/fooj
loginShell: /bin/bash
...
Size limit exceeded (4)
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Wildcard Matches> ldapsearch -LLL -x "(uid=smith*)"
dn: uid=smitha,ou=People,dc=gkar,dc=nku,dc=edu
uid: smitha
uidNumber: 10221
cn: smitha
homeDirectory: /home/f/smitha
loginShell: /bin/bash
...
dn:
uid: smithj
uidNumber: 12302
cn: smithj
homeDirectory: /home/g/smithj
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CIT 470: Advanced Network and System Administration Slide #24
Open source LDAPv3 server.– LDAP server: slapd– Client commands: ldapadd, ldapsearch– Backend storage: BerkeleyDB– Backend commands: slapadd, slapcat– Schemas: /etc/openldap/schema– Data: /var/lib/ldap
Configuration files– Client: /etc/openldap/ldap.conf– Server: /etc/openldap/slapd.conf
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Building an OpenLDAP Server
1. Install OpenLDAP.2. Configure LDAP for your domain.
Edit slapd.conf OR use Run Time Configuration (RTC)
3. Start serverImmediate: service ldap startPermanent: chkconfig --level 35 ldap on
4. Add data with ldapadd.5. Verify functionality with ldapsearch.
slapd.conf (Server)
File Locations (usually accept defaults)Schema files
Configuration files
Database directory
Databasesuffix = DN of topmost node in directory
rootdn = DN of LDAP administrative user
rootpw = Password of LDAP administrator
Access ControlCIT 470: Advanced Network and System Administration Slide #26
ldap.conf (Client)## LDAP Defaults#
# See ldap.conf(5) for details# This file should be world readable but not world
writable.
#BASE dc=example,dc=com (match suffix in slapd.conf)#URI ldap://ldap.example.com ldap://ldap-
master.example.com:666
#SIZELIMIT 12#TIMELIMIT 15#DEREF never
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References1. Brian Arkills, LDAP Directories Explained: An Introduction and
Analysis, Addison-Wesley, 2003.2. Gerald Carter, LDAP System Administration, O’Reilly, 2003.3. LDAP Howtos, Links, and Whitepapers, http://www.bind9.net/ldap/,
2005.4. http://www.ldapman.org/, 2005.5. LDAP for Rocket Scientists, http://www.zytrax.com/books/ldap/,
2009.6. Thomas Limoncelli, Christine Hogan, Strata Chalup, The Practice of
System and Network Administration, 2nd ed, Limoncelli and Hogan, Addison-Wesley, 2007.
7. Luiz Malere, “Linux LDAP HOWTO,” http://www.tldp.org/HOWTO/LDAP-HOWTO/, 2004.
8. Evi Nemeth et al, UNIX System Administration Handbook, 3rd edition, Prentice Hall, 2001.
9. OpenLDAP, OpenLDAP Administrator’s Guide, http://www.openldap.org/devel/admin/, 2005.