Crafting a Custom Schema in OpenLDAP: A Step-by-Step Guide


What is OpenLDAP?

OpenLDAP stands for Lightweight Directory Access Protocol (LDAP) and is a powerful open-source implementation of the LDAP protocol. OpenLDAP is a popular choice for managing directory services because it is free, customizable, and supports a wide range of authentication methods. The main function of OpenLDAP is to manage information about users, groups, devices, and other resources on a network.

The Importance of OpenLDAP in Managing Directory Services

OpenLDAP plays a critical role in managing directory services for organizations by providing an easy way to store user data and access it quickly. Without LDAP, administrators would need to manually manage user data across multiple servers and directories which can be both time-consuming and error-prone. With OpenLDAP, administrators can centralize their user data which simplifies authentication processes and improves overall network security.

The Importance of Custom Schemas in OpenLDAP

In addition to standard schemas that are included with OpenLDAP, the ability to create custom schemas enables administrators to expand on the functionality of their directory service by adding new attributes or object classes that are specific to their organization’s needs. Custom schemas allow organizations to tailor their directory service based on their specific requirements such as additional information needed for user accounts or unique devices used within their environment. By having the power to create custom schemas within OpenLDAP, administrators can easily manage all types of resources in one centralized location without needing complex workarounds or additional software solutions.

Understanding Schemas in OpenLDAP

Overview of Schemas and their Role in OpenLDAP

OpenLDAP is a widely-used open-source implementation of the Lightweight Directory Access Protocol (LDAP). LDAP is used for managing directory services such as user accounts, groups, and other organizational information.

A schema defines the structure of a directory service and specifies the types of objects that can be stored within it. The schema is an essential component of any LDAP-based directory service, allowing administrators to define the data elements that will be stored in the database.

In OpenLDAP, schemas play a critical role in defining and managing directory services. The schema defines the structure of the directory service and identifies all object classes and attributes that can be used to create objects.

Object classes are templates for creating objects within an LDAP database, while attributes provide additional information about those objects. Understanding schemas in OpenLDAP is essential for anyone involved in setting up or administering an LDAP-based directory service.

Types of Schemas Available in OpenLDAP

There are two primary types of schemas available in OpenLDAP: core schemas and custom schemas. Core schemas are pre-defined by the software vendor and are designed to provide basic functionality out-of-the-box. These schemas include commonly-used object classes such as user accounts and groups as well as standard attributes like name, email address, phone number, etc.

Custom schemas can be created by administrators to define new object classes or add additional attributes to existing ones beyond what is provided by core schemas. This allows organizations to tailor their directory services to meet specific needs or business requirements that may not be covered by core schemas.

In addition to core and custom schemas, there are also several other types of schema available including syntaxes (which define how values are represented), matching rules (which specify how attribute values should be compared), and ordering rules (which determine how attribute values should be sorted). These can be used to further customize and refine the structure of an LDAP-based directory service.

Preparing for Custom Schema Creation

Understanding the Requirements for Custom Schema Creation

Before creating a custom schema in OpenLDAP, it is important to understand the requirements and prerequisites for its creation. The first requirement is an understanding of LDAP and OpenLDAP directory services. This includes knowledge about object classes, attributes, syntaxes, and other elements of LDAP directory services.

Additionally, you should have prior experience with OpenLDAP server administration. Another requirement is an accurate identification of the attributes and object classes that are required in the schema.

It is important to identify all the attributes that will be used within your organization’s directory service before creating a custom schema. This can be achieved by analyzing business needs and processes, determining data objects, and establishing naming rules.

Identifying the Attributes and Object Classes Needed for the Schema

The next step is identifying the list of object classes needed for your custom schema. Object classes define attributes that apply to specific objects in an LDAP directory service. Once you have identified all necessary object classes, you need to determine their hierarchical order by defining parent-child relationships between them.

In addition to identifying object classes, it is also important to identify all required attributes based on business processes or organizational structure. The attribute types should be defined accurately using syntaxes from existing LDAP standards or new ones can be defined according to your organization’s specific needs.

After identifying required attributes and object classes, you need to decide which existing schema files can serve as templates for your custom schema file creation process. This step helps save time during schema creation as opposed to starting from scratch.

Taking Time on Preparation Yields Better Results

Before creating a custom schema in OpenLDAP it is essential that one understands LDAP concepts thoroughly such as syntaxes; have prior experience with OpenLDAP server administration; establish data objects; determine naming rules; and define the order of object classes and their parent-child relationships. Identifying attributes and object classes is fundamental in creating custom schemas, a thorough analysis of business processes will guide this task. Taking time at the preparation stage not only ensures better results but also saves time in the schema creation process.

Creating a Custom Schema Step-by-Step

Creating Object Classes

To create an object class in OpenLDAP, we need to define the name of the class, its OID (Object Identifier), an optional description, and its parent class. The parent class is the object class that our new class will inherit from. To create the object class ‘myPerson’, we will use this command: “`

objectclass ( NAME ‘myPerson’ DESC ‘My custom person entry’ SUP inetOrgPerson STRUCTURAL MUST ( cn $ sn ) MAY ( givenName $ streetAddress $ telephoneNumber ) ) “` In this command, we have defined myPerson as a structural objectclass that inherits from inetOrgPerson and has required attributes cn and sn while having optional attributes givenName, streetAddress, and telephoneNumber.

Creating Attributes

Attributes define the properties or characteristics of an object in OpenLDAP directory service schema. An attribute consists of a unique name or OID and one or more syntaxes which determine the format of values held by the attribute.

To define an attribute type in OpenLDAP schema, use a command like this one: “` attributetype ( DESC ‘My custom attribute’ SYNTAX 1.3 .6 .1 .4 .1 .1466 .115 .121 .1 .15 X-ORIGIN ‘My Company’ ) “`

This defines an attribute with OID “1.2..3…4….5…6” named “myCustomAttribute”. The syntax for this attribute is “Directory String” defined as “SYNTAX 1..3…6….1…..4…..1466…115..121..etc.”.

Modifying Existing Schema Files

When modifying existing schema files, it is important to understand their structure. The schema files are typically located in the /etc/openldap/schema directory and have a “.schema” extension. The syntax for editing an existing object class or attribute type involves updating its definition in the schema file.

For instance, if we want to add our custom attribute ( as a MAY attribute to the myPerson object class, we would locate the definition of myPerson in the schema file and modify it like so: “` objectclass ( 1 .

2 . 840 . 113556 . 1 . 6 . 165 NAME ‘myPerson’ DESC ‘My custom person entry’ SUP inetOrgPerson STRUCTURAL MUST ( cn $ sn ) MAY ( givenName $ streetAddress $ telephoneNumber $ myCustomAttribute ) ) “` This adds “myCustomAttribute” to the list of MAY attributes for this object class.

Testing and Deploying Custom Schemas on OpenLDAP

Testing the Custom Schema

To test whether our custom schema has been applied successfully, we can use LDAP tools such as ldapsearch or Apache Directory Studio. Using ldapsearch tool, as an example, you would run: “`ldapsearch -D “cn=admin,cn=config” -w password -b “dc=example, dc=com” “(objectClass=myPerson)”“`

This command searches for all entries with objectClass equal to ‘myPerson’. A successful search confirms that our custom schema has been applied correctly.

Deploying the Custom Schema on OpenLDAP Server

Once testing is complete and we’ve verified that our custom schema is working correctly on our development environment server, it’s time to deploy it on a production server. To deploy a custom schema onto an OpenLDAP server, we need to copy the schema file to /etc/openldap/schema directory on the production server.

We then need to modify the slapd.conf file and add an include statement for our custom schema. The include statement looks like this: “`

include /etc/openldap/schema/customschema.schema “` Once we have saved the changes in the slapd.conf file, we can restart OpenLDAP service to apply our changes.


OpenLDAP serves as a highly dependable tool in managing directory services. Creating custom schemas is an essential part of using OpenLDAP effectively.

With this guide, you should now be able to create your own customized schema that fits your organization’s requirements and deploy it on OpenLDAP servers with ease. Custom schemas facilitate better management of directories by allowing custom classes and attributes tailored to organizational needs while maintaining compliance with standards.

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