How to Rebuild a Database (BDB, HDB) in OpenLDAP


Brief Overview of OpenLDAP and its Importance in Managing Directory Services

OpenLDAP is a widely used open-source implementation of the Lightweight Directory Access Protocol (LDAP). It provides an efficient and flexible way to manage directory services, which is essential for any organization that needs to maintain a centralized database of user, group, or resource information.

OpenLDAP can be used for various purposes such as authentication, authorization, and accounting (AAA); it is also used by many cloud applications like Google Cloud Identity. OpenLDAP has many advantages over other directory service providers such as Microsoft Active Directory or Apple Open Directory.

One of the notable advantages is its platform independence. Unlike Active Directory, which can only be installed on Windows servers, OpenLDAP can be deployed on different operating systems including Windows, Linux, Unix-like systems like Solaris or FreeBSD OSes.

Explanation of What a Database Is and Its Significance in OpenLDAP

A database is an organized collection of data that can be accessed and managed by computer programs. In the context of OpenLDAP, a database contains all the information about users, groups, resources or any other objects stored in the directory service.

The significance of the database in OpenLDAP lies in how it stores and organizes data. Two types of databases are commonly used with OpenLDAP: Berkeley DB (BDB) and Hierarchical Data Base (HDB).

BDB uses key-value pairs to store data while HDB uses an indexed tree structure that enables faster search operations. Both databases have their own advantages depending on your use case.

Since LDAP queries are often complex and require many lookups to find desired information from different directories serving different purposes within an organization. A well-organized database structure optimized for these queries will minimize search times and improve system efficiency overall.

Understanding BDB and HDB Databases

OpenLDAP is an open-source implementation of the Lightweight Directory Access Protocol (LDAP) that provides a centralized location for storing and managing directory services. A database is a critical component of OpenLDAP, which stores the directory data in an organized structure to provide efficient read/write operations. OpenLDAP supports two primary types of databases: Berkeley Database (BDB) and Hierarchical Database (HDB).

Definition of BDB and HDB Databases

BDB is a widely used open-source embedded database library that provides high-performance access to large data sets. BDB supports several data structures, including key-value pairs, associative arrays, and tables. In contrast, HDB is a module included with OpenLDAP that uses the Lightweight Directory Access Protocol Data Interchange Format (LDIF) to store the directory data in hierarchical form.

Differences between the two types of databases

The significant difference between BDB and HBD is how they organize the directory data. BDB stores data in key-value pairs or tables with indices for efficient access while HBD organizes data based on its hierarchical nature using LDIF format.

The design decisions made while choosing one type over another can have a considerable impact on your application’s performance. Another difference between them lies in their ability to handle high concurrency levels: While both are known for handling high concurrency levels well, some tests show that Berkeley DB outperforms Hierarchical DB slightly when it comes to concurrency.

Advantages and disadvantages of using each type

One advantage of using BDB over HBD is its speed when handling massive datasets due to its indexing capabilities. Because it’s optimized for key-value lookup operations, it has fast read-write times if you have large datasets with multiple concurrent reads/writes going on at once. On the other hand, if you have a relatively small dataset, HBD may be more beneficial as it allows you to quickly search through the data using common tools such as grep without creating an index.

However, because HBD is hierarchical, querying certain parts of the directory can sometimes be slower than other methods. Choosing the right database type depends on your application’s specific needs.

If you require fast read/write times for large datasets and don’t need immediate access to all entries in your dataset, BDB might be the better choice. Whereas if you have a smaller dataset that requires quick access to specific entries and easy searching capabilities, HDB might be more beneficial.

Reasons for Rebuilding a Database

Databases are the backbone of any OpenLDAP installation, and they need to be managed carefully to ensure optimal performance. However, even with the best management practices, databases can become corrupt and unusable. When this happens, it may be necessary to rebuild the database from scratch.

There are many reasons why a database may need to be rebuilt. One common reason is when there is corruption in the database files due to various factors such as hardware failure, software bugs or power outages.

Another reason could be due to issues with disk space allocation resulting in data fragmentation which can slow down the performance of the system. Additionally, administrators may need to rebuild a new schema or migrate data between LDAP servers.

Common reasons why a database may need to be rebuilt

One of the most common reasons for rebuilding an OpenLDAP database is when there has been data corruption or loss due to hardware failure or file system issues. This can result in missing records or complete loss of data which impacts business continuity and essential services.

Another frequent cause for rebuilding a database is when there are performance issues caused by disk fragmentation or file system errors resulting from disk space shortages that can lead to slow queries and increased query times leading up-to timeouts eventually failing services. Administrators may also wish to restructure an existing schema by changing object classes and attribute names involved this process usually requires rebuilding all databases affected by changes made prior.

Importance of backing up data before rebuilding

Before initiating any major changes such as reconstructing a vital part like OpenLDAP databases it’s crucial always proper backups have been taken so that you can restore your installation if anything goes wrong during the rebuild process. Backups should include not only your OpenLDAP configurations but also any associated log files, SSL keys and certificates as well as other data associated with your setup that could help during restoration. The backup strategy should be tailored to your setup; databases such as BDB and HDB require different backup strategies.

Therefore, it’s good practice to research the best method for each case and always document the process to make sure you don’t miss any critical steps. Thus, backing up data is a crucial step before rebuilding databases in OpenLDAP not only does it ensure business continuity in case of failure; it also helps you save time and effort by not having to rebuild your data from scratch or seeking support from third-party vendors.

Steps to Rebuild a BDB Database in OpenLDAP

Stop the LDAP server

The first step in rebuilding a BDB database in OpenLDAP is to stop the LDAP server. This is necessary because the server needs to be shut down before any changes can be made to the database files. To stop the server, you can use the command “service ldap stop” or “systemctl stop slapd” depending on your system configuration.

Backup the existing database files

The next step is to create a backup of your existing database files. This is important because it will allow you to restore your data if anything goes wrong during the rebuilding process.

To create a backup, you can use the slapcat command which will dump all contents of your OpenLDAP directory into an LDIF file. For example, you can run “slapcat -v -l backup.ldif” and it will create a file named “backup.ldif” containing all your existing data.

Remove the old database files

After creating a backup, you need to remove all old database files associated with BDB. The easiest way is to go into your /var/lib/ldap directory and delete all files with extensions ending in .bdb or .db. For example, if you have two databases named “internal” and “external”, then their respective files would be internal.bdb and external.bdb.

Create a new empty database file

Now that you’ve removed all old BDB databases from OpenLDAP, it’s time to create new empty ones. You can do this by running “slapadd -n 0 -l /dev/null -F /etc/openldap/slapd.d” command which creates an empty configuration tree.

Import data from backup files into new database file

After creating a new empty database, you can import data from the backup files using the slapadd command. For example, if your backup file is named “backup.ldif”, then you can run “slapadd -v -l backup.ldif” to import all data from the backup file into your new BDB database.

Start the LDAP server

After completing all previous steps of rebuilding a BDB database in OpenLDAP, it’s time to start the LDAP server again with “service ldap start” or “systemctl start slapd”. The newly created databases will now be available for use in OpenLDAP and contain all necessary data previously backed up.

Steps to Rebuild an HDB Database in OpenLDAP

Stop the LDAP server

Before starting the process of rebuilding an HDB database in OpenLDAP, it is necessary to stop the LDAP server. This ensures that no new data is written to the existing HDB database while it is being rebuilt. To stop the LDAP server, use the appropriate command for your system.

For example, on a Linux-based system, you can use: “` sudo systemctl stop slapd “`

Backup the existing database files

Creating a backup of your existing HDB database files is essential before proceeding with any type of reconstruction work. It ensures that you can recover all important data in case something goes wrong during the rebuild process.

To make a backup of your existing HDB database files, you need to copy all relevant files and store them safely somewhere outside your OpenLDAP directory tree. You should create one backup file for each partition or backend that you are going to rebuild.

For example, if you have two partitions named “dc=example,dc=com” and “ou=people”, then you would need to create two backups as follows: “` sudo cp /var/lib/ldap/ /root/backups/

sudo cp /var/lib/ldap/people.hdb /root/backups/people.hdb.backup “` Make sure that these files are readable only by root user.

Remove old database files

After taking a backup of your existing HDB databases, remove their old versions from your system. For this purpose, first navigate to the directory containing all databases: “` cd /var/lib/ldap/ “`

Then remove old versions of BDB and other databases using following commands: “` sudo rm -f *.bdb

sudo rm -f *.gdbm sudo rm -f *.db “`

Similarly, remove old HDB database files using following command: “` sudo rm -f *.hdb “`

Create a new empty database file with correct permissions

After removing the old database files, create a new empty database file for each of your partitions. Make sure that the ownership and permissions of the newly created files are set correctly.

The OpenLDAP server should be able to read and write these files. For example, to create an empty HDB database file for partition “dc=example,dc=com”, use: “`

sudo touch /var/lib/ldap/ sudo chown openldap:openldap /var/lib/ldap/

sudo chmod 600 /var/lib/ldap/ “` Note: Replace “” with your domain name and change ownership and permission for other partitions accordingly.

Import data from backup files into new database file using slapadd command

Now that you have created an empty HDB database file with correct permissions, it’s time to import data from your backup file(s) into the new database using the “slapadd” command. For example, to import data from backup file “/root/backups/” into newly created database for partition “dc=example,dc=com”, use: “`

slapadd -q -n 0 -F /etc/openldap/slapd.d -l /root/backups/ -b dc=example,dc=com “` Similarly, repeat above process for each partition or backend you want to rebuild.

Start LDAP Server

The final step is to start LDAP server again so that you can access newly rebuilt databases. You can start it by running following command: “` sudo systemctl start slapd “`

Rebuilding HDB database in OpenLDAP is a critical task that requires careful planning and execution. Follow above mentioned steps carefully to avoid any data loss or corruption.

Troubleshooting Tips for Common Issues during Database Re

Dealing with Access Control Issues

One of the most common issues that arise during database rebuilds is access control errors. These occur when the permissions or ownership of the files have not been set correctly.

First, make sure that you have correctly set the ownership and permissions of all files involved in the rebuild process. If you are still experiencing issues, check your slapd.conf file to ensure there are no discrepancies between it and your database.

Debugging Configuration Errors

Another issue that can cause problems during a database rebuild is configuration errors. Make sure that your slapd.conf file has been configured correctly and matches any changes made during the rebuilding process. You should also check any logs generated by OpenLDAP to identify any configuration-related issues.

Troubleshooting Connection Problems

If you encounter connection problems, start by ensuring that all necessary services on your system are running properly. Verify that your network settings are correct and that OpenLDAP is listening on the correct IP address and port number. Check whether there is an issue with a firewall preventing access to port 389 or 636 (if using SSL).


Rebuilding a BDB or HDB database in OpenLDAP can be a complex task, but it is a critical skill for anyone working with directory services management. Although there are multiple steps involved in rebuilding these databases, following these outlined procedures will help ensure a successful result. Always take precautionary backups before attempting to rebuild any database and pay attention to detail when setting up new databases or restoring data from backup files.

Remember, troubleshooting common issues such as access control problems, configuration errors, or connection problems can sometimes be frustrating but they should not deter you from persisting toward achieving success. Mastering database rebuild techniques will make it easier to manage and maintain OpenLDAP, giving you more control over your directory services management.

Related Articles