Lightweight LDAP Server Alternatives to OpenLDAP for Small-Scale User Synchronization on Unix Systems


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Many sysadmins and developers working with small-scale deployments find OpenLDAP's configuration overhead disproportionate to their needs. The modern OpenLDAP (2.4+ versions) requires significant setup effort for basic use cases - precisely when you just need:

  • Simple user/group synchronization across a few machines
  • Centralized authentication for web applications
  • Basic posixAccount and groupOfNames support

Here are three battle-tested alternatives that work well on *nix systems:

1. 389 Directory Server (formerly Fedora Directory Server)

A robust yet simpler-to-configure option with good documentation. Installation on Ubuntu/Debian:


sudo apt-get install 389-ds-base
sudo dscreate from-file /usr/share/389-ds/base/inf/defaults.ldif

Sample minimal configuration for posix users:


dn: cn=posix,cn=plugins,cn=config
objectClass: top
objectClass: nsSlapdPlugin
objectClass: extensibleObject
cn: posix
nsslapd-pluginPath: libposix-winsync-plugin
nsslapd-pluginInitfunc: posix_winsync_init
nsslapd-pluginType: object
nsslapd-pluginEnabled: on

2. OpenDJ

Originally developed by Sun, now maintained by ForgeRock. Java-based but lightweight for small deployments:


wget https://maven.forgerock.org/repo/releases/org/forgerock/opendj/opendj-server/4.5.0/opendj-server-4.5.0.zip
unzip opendj-server-*.zip
./opendj/setup --cli

3. Samba4 as LDAP Server

Surprisingly effective for small Unix environments, especially if you need Windows compatibility:


sudo apt-get install samba smbldap-tools
sudo samba-tool domain provision --use-rfc2307 --interactive

The --use-rfc2307 flag enables Unix POSIX attributes.

When choosing between these options, consider:

  • Performance: OpenDJ performs best for read-heavy loads
  • Setup Time: 389 DS has the quickest initial configuration
  • Schema Extensions: Samba4 handles both Microsoft and Unix schemas well

If you need to eventually scale up to OpenLDAP, 389 DS provides the smoothest transition path with its standard LDIF format and similar operational characteristics.

After evaluating OpenLDAP's latest versions, I found the setup process unnecessarily complex for managing just 20-30 users across a few machines. The overhead of slapd configuration, schema management, and ACL tuning simply doesn't justify the benefits for small-scale deployments.

My core needs are straightforward:

  • Serve PosixAccount (inetOrgPerson + posixAccount) objects
  • Handle posixGroup objects
  • Basic CRUD operations via LDIF or CLI
  • Low-maintenance operation

1. 389 Directory Server (formerly Fedora Directory Server)

Surprisingly lightweight despite its enterprise roots. Install on CentOS/RHEL:

# dnf install 389-ds-base
# dscreate from-file /usr/share/389-ds/base/inf/defaults.inf

2. Samba4 as LDAP Server

Works great for posixAccount sync:

# apt install samba smbldap-tools
# smbpasswd -a username

3. OpenDJ

Java-based but surprisingly light:

wget https://github.com/OpenIdentityPlatform/OpenDJ/releases/download/4.4.11/opendj-4.4.11.zip
unzip opendj-4.4.11.zip
./OpenDJ/bin/setup --cli

After installation, add the posix schema:

ldapmodify -D "cn=Directory Manager" -W -a -f /usr/share/389-ds-base/ldif/ns-schema.ldif

Sample user entry:

dn: uid=jdoe,ou=People,dc=example,dc=com
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: inetOrgPerson
objectClass: posixAccount
uid: jdoe
cn: John Doe
sn: Doe
uidNumber: 1001
gidNumber: 100
homeDirectory: /home/jdoe
loginShell: /bin/bash

For <100 users, all mentioned solutions perform similarly. Memory usage benchmarks on Ubuntu 22.04:

  • 389DS: ~120MB RAM idle
  • Samba4: ~90MB RAM
  • OpenDJ: ~200MB RAM (JVM overhead)

If you need to scale up later, all solutions support LDIF exports compatible with OpenLDAP:

ldapsearch -LLL -x -D "cn=admin,dc=example,dc=com" -W -b "dc=example,dc=com" "*" > full_dump.ldif