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Applies to SUSE Linux Enterprise Server 15 SP6

5 LDAP with 389 Directory Server

 

The Lightweight Directory Access Protocol (LDAP) is a protocol designed to access and maintain information directories. LDAP can be used for tasks such as user and group management, system configuration management, and address management. In SUSE Linux Enterprise Server 15 SP6, the LDAP service is provided by the 389 Directory Server, replacing OpenLDAP.

Ideally, a central server stores the data in a directory and distributes it to all clients using a well-defined protocol. The structured data allow a wide range of applications to access them. A central repository reduces the necessary administrative effort. The use of an open and standardized protocol such as LDAP ensures that as many client applications as possible can access such information.

A directory in this context is a type of database optimized for quick and effective reading and searching. The type of data stored in a directory tends to be long lived and changes infrequently. This allows the LDAP service to be optimized for high performance concurrent reads, whereas conventional databases are optimized for accepting many writes to data in a short time.

5.1 Structure of an LDAP directory tree

 

This section introduces the layout of an LDAP directory tree, and provides the basic terminology used with regard to LDAP. If you are familiar with LDAP, read on at Section 5.3.1, “Setting up a new 389 Directory Server instance”.

An LDAP directory has a tree structure. All entries (called objects) of the directory have a defined position within this hierarchy. This hierarchy is called the directory information tree (DIT). The complete path to the desired entry, which unambiguously identifies it, is called the distinguished name or DN. An object in the tree is identified by its relative distinguished name (RDN). The distinguished name is built from the RDNs of all entries on the path to the entry.

The relations within an LDAP directory tree become more evident in the following example, shown in Figure 5.1, “Structure of an LDAP directory”.

Structure of an LDAP directory
Figure 5.1: Structure of an LDAP directory
 

The complete diagram is a fictional directory information tree. The entries on three levels are depicted. Each entry corresponds to one box in the image. The complete, valid distinguished name for the fictional employee Geeko Linux, in this case, is cn=Geeko Linux,ou=doc,dc=example,dc=com. It is composed by adding the RDN cn=Geeko Linux to the DN of the preceding entry ou=doc,dc=example,dc=com.

The types of objects that can be stored in the DIT are globally determined following a Schema. The type of an object is determined by the object class. The object class determines what attributes the relevant object must or may be assigned. The Schema contains all object classes and attributes which can be used by the LDAP server. Attributes are a structured data type. Their syntax, ordering and other behavior is defined by the Schema. LDAP servers supply a core set of Schemas which can work in a broad variety of environments. If a custom Schema is required, you can upload it to an LDAP server.

Table 5.1, “Commonly used object classes and attributes” offers a small overview of the object classes from 00core.ldif and 06inetorgperson.ldif used in the example, including required attributes (Req. Attr.) and valid attribute values. After installing 389 Directory Server, these can be found in /usr/share/dirsrv/schema.

Table 5.1: Commonly used object classes and attributes
 

Object Class

Meaning

Example Entry

Req. Attr.

domain

name components of the domain

example

displayName

organizationalUnit

organizational unit

documentationdept

ou

nsPerson

person-related data for the intranet or Internet

Tux Linux

cn

Example 5.1, “Excerpt from CN=schema” shows an excerpt from a Schema directive with explanations.

Example 5.1: Excerpt from CN=schema
 
attributetype (1.2.840.113556.1.2.102 NAME 'memberOf' 1
       DESC 'Group that the entry belongs to' 2
       SYNTAX 1.3.6.1.4.1.1466.115.121.1.12 3
       X-ORIGIN 'Netscape Delegated Administrator') 4

objectclass (2.16.840.1.113730.3.2.333 NAME 'nsPerson' 5
       DESC 'A representation of a person in a directory server' 6
       SUP top STRUCTURAL 7
       MUST ( displayName $ cn ) 8
       MAY ( userPassword $ seeAlso $ description $ legalName $ mail \
             $ preferredLanguage ) 9
       X-ORIGIN '389 Directory Server Project'
  ...

1

The name of the attribute, its unique object identifier (OID, numerical), and the abbreviation of the attribute.

2

A brief description of the attribute with DESC. The corresponding RFC, on which the definition is based, may also mentioned here.

3

The type of data that can be held in the attribute. In this case, it is a case-insensitive directory string.

4

The source of the schema element (for example, the name of the project).

5

The definition of the object class nsPerson begins with an OID and the name of the object class (like the definition of the attribute).

6

A brief description of the object class.

7

The SUP top entry indicates that this object class is not subordinate to another object class.

8

With MUST, list all attribute types that must be used with an object of the type nsPerson.

9

With MAY, list all attribute types that are optionally permitted with this object class.

5.2 Creating and managing a Docker container for 389 Directory Server

 
Note
Note

This section is OPTIONAL; refer to it if you use a 389 Directory Server instance as a Docker container. For regular usage of a 389 Directory Server instance, refer to the rest of the sections.

To create and manage a 389 Directory Server instance as a Docker container, refer to the following examples:

Pull the latest 389 Directory Server image

To pull the latest 389 Directory Server image from the container registry, run the following command: 

>  docker pull 389ds/dirsrv:latest
Create a new volume

To create a new volume for the container, run the following example command: 

>  docker volume create VOLUME
Create a container with basic configuration

To create a container with basic configuration, run the following example command: 

>  docker create \
 -u USERNAME \
 -e SUFFIX_NAME="dc=example,dc=com" \
 -e DS_DM_PASSWORD=PASSWORD \
 -m 1024M \
 -p 3389:3389 -p 3636:3636 \
 -v VOLUME:/data \
 --name INSTANCE \
 389ds/dirsrv:latest
Start the Docker container for 389 Directory Server

To start the Docker container, run the following example command: 

>  docker start INSTANCE
Execute a command within a running 389 Directory Server container

Assuming that the primary process of the container (PID 1) is running, you can run a command within a running 389 Directory Server container by using the following syntax: 

> sudo docker exec -u USERNAME -i -t INSTANCE COMMAND
Note
Note: The COMMAND must be executable

To run a chained command or a command enclosed within quotations, you should first run a shell session in the container. For example, you can run commands in the sh shell attached to the container: 

> sudo docker exec -u USERNAME -i -t INSTANCE sh -c "COMMAND"
Stop the Docker container for 389 Directory Server

To stop the running Docker container, run the following example command: 

>  docker stop INSTANCE
Remove the Docker container for 389 Directory Server

To remove the Docker container, run the following example command: 

>  docker rm INSTANCE

5.3 Installing 389 Directory Server

 

Install 389 Directory Server with the following command: 

> sudo zypper install 389-ds

After installation, set up the server as described in Section 5.3.1, “Setting up a new 389 Directory Server instance”.

5.3.1 Setting up a new 389 Directory Server instance

 

You will use the dscreate command to create new 389 Directory Server instances, and the dsctl command to cleanly remove them.

There are two ways to configure and create a new instance: from a custom configuration file, and from an auto-generated template file. You can use the auto-generated template without changes for a test instance, though for a production system you must carefully review it and make any necessary changes.

Then you will set up administration credentials, manage users and groups, and configure identity services.

The 389 Directory Server is controlled by three primary commands:

dsctl

Manages a local instance and requires root permissions. Requires you to be connected to a terminal which is running the directory server instance. Used for starting, stopping, backing up the database, and more.

dsconf

The primary tool used for administration and configuration of the server. Manages an instance's configuration via its external interfaces. This allows you to make configuration changes remotely on the instance.

dsidm

Used for identity management (managing users, groups, passwords, etc.). The permissions are granted by access controls, so, for example, users can reset their own password or change details of their own account.

Follow these steps to set up a simple instance for testing and development, populated with a small set of sample entries.

  1. Creating a 389 Directory Server instance with a custom configuration file

  2. Creating a 389 Directory Server instance from a template

  3. Configuring administrator credentials for local administration

  4. Managing LDAP users and groups

  5. Using SSSD to manage LDAP authentication

  6. Managing plug-ins

  7. Importing TLS server certificates and keys

5.3.2 Creating a 389 Directory Server instance with a custom configuration file

 

You can create a new 389 Directory Server instance from a simple custom configuration file. This file must be in the INF format, and you can name it anything you like.

The default instance name is localhost. The instance name cannot be changed after it has been created. It is better to create your own instance name, rather than using the default, to avoid confusion and to enable a better understanding of how it all works. The following examples use the LDAP1 instance name, and a suffix of dc=LDAP1,dc=COM.

Example 5.2 shows an example configuration file that you can use to create a new 389 Directory Server instance. You can copy and use this file without changes.

  1. Copy the following example file, LDAP1.inf, to your home directory:

    Example 5.2: Minimal 389 Directory Server instance configuration file
     
    # LDAP1.inf

[general]
config_version = 2 1

[slapd]
root_password = PASSWORD2
self_sign_cert = True 3
instance_name = LDAP1

[backend-userroot]
sample_entries = yes 4
suffix = dc=LDAP1,dc=COM

    1

    This line is required, indicating that this is a version 2 setup INF file.

    2

    Create a strong root_password for the ldap user cn=Directory Manager. This user is for connecting (binding) to the directory.

    3

    Create self-signed server certificates in /etc/dirsrv/slapd-LDAP1.

    4

    Populate the new instance with sample user and group entries.

  2. To create the 389 Directory Server instance from Example 5.2, run the following command: 

    > sudo dscreate -v from-file LDAP1.inf | \
tee LDAP1-OUTPUT.txt

    This shows all activity during the instance creation, stores all the messages in LDAP1-OUTPUT.txt, and creates a working LDAP server in about a minute. The verbose output contains a lot of useful information. If you do not want to save it, then delete the | tee LDAP1-OUTPUT.txt portion of the command.

  3. If the dscreate command should fail, the messages will tell you why. After correcting any issues, remove the instance (see Step 5) and create a new instance.

  4. A successful installation reports Completed installation for LDAP1. Check the status of your new server: 

    > sudo dsctl LDAP1 status
Instance "LDAP1" is running

  5. The following commands are for cleanly removing the instance. The first command performs a dry run and does not remove the instance. When you are sure you want to remove it, use the second command with the --do-it option: 

    > sudo dsctl LDAP1 remove
Not removing: if you are sure, add --do-it

> sudo dsctlLDAP1 remove --do-it

    This command also removes partially installed or corrupted instances. You can reliably create and remove instances as often as you want.

If you forget the name of your instance, use dsctl to list all instances: 

> sudo dsctl -l
slapd-LDAP1

5.3.3 Creating a 389 Directory Server instance from a template

 

You can auto-create a template for a new 389 Directory Server instance with the dscreate command. This creates a template that you can use without making any changes, for testing. For production systems, review and change it to suit your own requirements. The defaults are documented in the template file, and commented out. To make changes, uncomment the default and enter your own value. All options are well documented.

The following example prints the template to stdout: 

> sudo dscreate create-template

This is good for a quick review of the template, but you must create a file to use in creating your new 389 Directory Server instance. You can name this file anything you want: 

> sudo dscreate create-template TEMPLATE.txt

This is a snippet from the new file: 

# full_machine_name (str)
# Description: Sets the fully qualified hostname (FQDN) of this system. When
# installing this instance with GSSAPI authentication behind a load balancer, set
# this parameter to the FQDN of the load balancer and, additionally, set
# "strict_host_checking" to "false".
# Default value: ldapserver1.test.net
;full_machine_name = ldapserver1.test.net

# selinux (bool)
# Description: Enables SELinux detection and integration during the installation
# of this instance. If set to "True", dscreate auto-detects whether SELinux is
# enabled. Set this parameter only to "False" in a development environment.
# Default value: True
;selinux = True

It automatically configures certain options from your existing environment; for example, the system's fully-qualified domain name, which is called full_machine_name in the template. Use this file with no changes to create a new instance: 

> sudo dscreate from-file TEMPLATE.txt

This creates a new instance named localhost, and automatically starts it after creation: 

> sudo dsctl localhost status
Instance "localhost" is running

The default values create a fully operational instance, but there are certain values you might want to change.

The instance name cannot be changed after it has been created. It is better to create your own instance name, rather than using the default, to avoid confusion and to enable a better understanding of how it all works. To do this, uncomment the ;instance_name = localhost line and change localhost to your chosen name. In the following examples, the instance name is LDAP1.

Another useful change is to populate your new instance with sample users and groups. Uncomment ;sample_entries = no and change no to yes. This creates the demo_user and demo_group.

Set your own password by uncommenting ;root_password, and replacing the default password with your own.

The template does not create a default suffix, so you should configure your own on the suffix line, like the following example: 

suffix = dc=LDAP1,dc=COM

You can cleanly remove any instance and start over with dsctl: 

> sudo dsctl LDAP1 remove --do-it

5.3.4 Stopping and starting 389 Directory Server

 

The following examples use LDAP1 as the instance name. Use systemd to manage your 389 Directory Server instance. Get the status of your instance: 

> systemctl status --no-pager --full dirsrv@LDAP1.service
   ● dirsrv@LDAP1.service - 389 Directory Server LDAP1.
     Loaded: loaded (/usr/lib/systemd/system/dirsrv@.service; enabled; vendor preset: disabled)
     Active: active (running) since Thu 2021-03-11 08:55:28 PST; 2h 7min ago
    Process: 4451 ExecStartPre=/usr/lib/dirsrv/ds_systemd_ask_password_acl
       /etc/dirsrv/slapd-LDAP1/dse.ldif (code=exited, status=0/SUCCESS)
   Main PID: 4456 (ns-slapd)
     Status: "slapd started: Ready to process requests"
      Tasks: 26
     CGroup: /system.slice/system-dirsrv.slice/dirsrv@LDAP1.service
             └─4456 /usr/sbin/ns-slapd -D /etc/dirsrv/slapd-LDAP1 -i /run/dirsrv/slapd-LDAP1.pid

Start, stop and restart your LDAP server: 

> sudo systemctl start dirsrv@LDAP1.service
> sudo systemctl stop dirsrv@LDAP1.service
> sudo systemctl restart dirsrv@LDAP1.service

See Chapter 19, The systemd daemon for more information on using systemctl.

The dsctl command also starts and stops your server: 

> sudo dsctl LDAP1 status
> sudo dsctl LDAP1 stop
> sudo dsctl LDAP1 restart
> sudo dsctl LDAP1 start

5.3.5 Configuring administrator credentials for local administration

 

For local administration of the 389 Directory Server, you can create a .dsrc configuration file in the /root directory, allowing root and sudo users to administer the server without typing connection details with every command. Example 5.3 shows an example for local administration on the server, using LDAP1 and com for the suffix.

After creating your /root/.dsrc file, try a few administration commands, such as creating new users (see Section 5.6, “Managing LDAP users and groups”).

Example 5.3: A .dsrc file for local administration
 
# /root/.dsrc file for administering the LDAP1 instance

[LDAP1] 1

uri = ldapi://%%2fvar%%2frun%%2fslapd-LDAP1.socket 2
basedn = dc=LDAP1,dc=COM
binddn = cn=Directory Manager

1

This must specify your exact instance name.

2

ldapi detects the UID and GID of the user attempting to log in to the server. If the UID/GID are 0/0 or dirsrv:dirsrv, ldapi binds the user as the directory server root dn, which is cn=Directory Manager.

In the URI, the slashes are replaced with %%2f, so in this example the path is /var/run/slapd-LDAP1.socket.

Important
Important: New negation feature in sudoers.ldap

In sudo versions older than 1.9.9, negation in sudoers.ldap does not work for the sudoUser, sudoRunAsUser, or sudoRunAsGroup attributes. For example: 

 # does not match all but joe
# instead, it does not match anyone
sudoUser: !joe

# does not match all but joe
# instead, it matches everyone including Joe
sudoUser: ALL
sudoUser: !joe

In sudo version 1.9.9 and higher, negation is enabled for the sudoUser attribute. See man 5 sudoers.ldap for more information.

5.4 Firewall configuration

 

The default TCP ports for 389 Directory Server are 389 and 636. TCP 389 is for unencrypted connections, and STARTTLS. 636 is for encrypted connections over TLS.

firewalld is the default firewall manager for SUSE Linux Enterprise Server. The following rules activate the ldap and ldaps firewall services: 

> sudo firewall-cmd --add-service=ldap --zone=internal
> sudo firewall-cmd --add-service=ldaps --zone=internal
> sudo firewall-cmd --runtime-to-permanent

Replace the zone with the appropriate zone for your server. See Section 5.10, “Importing TLS server certificates and keys” for information on securing your connections with TLS, and Section 23.3, “Firewalling basics” to learn about firewalld.

5.5 Backing up and restoring 389 Directory Server

 

389 Directory Server supports making offline and online backups. The dsctl command makes offline database backups, and the dsconf command makes online database backups. Back up the LDAP server configuration directory to enable complete restoration in case of a major failure.

5.5.1 Backing up the LDAP server configuration

 

Your LDAP server configuration is in the directory /etc/dirsrv/slapd-INSTANCE_NAME. This directory contains certificates, keys and the dse.ldif file. Make a compressed backup of this directory with the tar command: 

> sudo tar caf \
config_slapd-INSTANCE_NAME-$(date +%Y-%m-%d_%H-%M-%S).tar.gz \
/etc/dirsrv/slapd-INSTANCE_NAME/
Note
Note: Harmless tar error message

When running tar, you may see the harmless informational message tar: Removing leading `/' from member names.

To restore a previous configuration, unpack it to the same directory:

  1. (Optional) To avoid overwriting an existing configuration, move it: 

    > sudo old /etc/dirsrv/slapd-INSTANCE_NAME/

  2. Unpack the backup archive: 

    > sudo tar -xvzf \
config_slapd-INSTANCE_NAME-DATE.tar.gz

  3. Copy it to /etc/dirsrv/slapd-INSTANCE_NAME: 

    > sudo cp -r etc/dirsrv/slapd-INSTANCE_NAME \
/etc/dirsrv/slapd-INSTANCE_NAME

5.5.2 Creating an offline backup of the LDAP database and restoring from it

 

The dsctl command makes offline backups. Stop the server: 

> sudo dsctl INSTANCE_NAME stop
Instance "INSTANCE_NAME" has been stopped

Then make the backup using your instance name. The following example creates a backup archive at /var/lib/dirsrv/slapd-INSTANCE_NAME/bak/INSTANCE_NAME-DATE: 

> sudo dsctl INSTANCE_NAME db2bak
db2bak successful

For example, on a test instance named ldap1 it looks like this: 

/var/lib/dirsrv/slapd-ldap1/bak/ldap1-2021_10_25_13_03_17

Restore from this backup, naming the directory containing the backup archive: 

> sudo dsctl INSTANCE_NAME bak2db \
/var/lib/dirsrv/slapd-INSTANCE_NAME/bak/INSTANCE_NAME-DATE/
bak2db successful

Then start the server: 

> sudo dsctl INSTANCE_NAME start
Instance "INSTANCE_NAME" has been started

You can also create LDIF backups: 

> sudo dsctl INSTANCE_NAME db2ldif --replication userRoot
ldiffile: /var/lib/dirsrv/slapd-INSTANCE_NAME/ldif/INSTANCE_NAME-userRoot-DATE.ldif
db2ldif successful

Restore an LDIF backup with the name of the archive, then start the server: 

> sudo dsctl ldif2db userRoot \
/var/lib/dirsrv/slapd-INSTANCE_NAME/ldif/INSTANCE_NAME-userRoot-DATE.ldif
> sudo dsctl INSTANCE_NAME start

5.5.3 Creating an online backup of the LDAP database and restoring from it

 

Use the dsconf to make an online backup of your LDAP database: 

> sudo dsconf INSTANCE_NAME backup create
The backup create task has finished successfully

This creates /var/lib/dirsrv/slapd-INSTANCE_NAME/bak/INSTANCE_NAME-DATE.

Restore it: 

> sudo dsconf INSTANCE_NAME backup restore \
/var/lib/dirsrv/slapd-INSTANCE_NAME/bak/INSTANCE_NAME-DATE

5.6 Managing LDAP users and groups

 

Use the dsidm command to create, remove and manage users and groups.

5.6.1 Querying existing LDAP users and groups

 

The following examples show how to list your existing users and groups. The examples use the instance name LDAP1. Replace this with your instance name: 

> sudo dsidm LDAP1 user list
> sudo dsidm LDAP1 group list

List all information on a single user: 

> sudo dsidm LDAP1 user get USER

List all information on a single group: 

> sudo dsidm LDAP1 group get GROUP

List members of a group: 

> sudo dsidm LDAP1 group members GROUP

5.6.2 Creating users and managing passwords

 

In the following example, we create one user, wilber. The example server instance is named LDAP1, and the instance's suffix is dc=LDAP1,dc=COM.

Procedure 5.1: Creating LDAP users
 

The following example creates the user Wilber Fox on your 389 DS instance: 

  1. > sudo dsidm LDAP1 user create --uid wilber \
  --cn wilber --displayName 'Wilber Fox' --uidNumber 1001 --gidNumber 101 \
  --homeDirectory /home/wilber

  2. Verify by looking up your new user's distinguished name (fully qualified name to the directory object, which is guaranteed unique): 

    > sudo dsidm LDAP1 user get wilber
dn: uid=wilber,ou=people,dc=LDAP1,dc=COM
[...]

    You need the distinguished name for actions such as changing the password for a user.

  3. Create a password for new user wilber: 

    1. > sudo dsidm LDAP1 account reset_password \
  uid=wilber,ou=people,dc=LDAP1,dc=COM

    2. Enter the new password for wilber twice.

      If the action was successful, you get the following message: 

      reset password for uid=wilber,ou=people,dc=LDAP1,dc=COM

      Use the same command to change an existing password.

  4. Verify that the user's password works: 

    > ldapwhoami -D uid=wilber,ou=people,dc=LDAP1,dc=COM -W
Enter LDAP Password: PASSWORD
dn: uid=wilber,ou=people,dc=LDAP1,dc=COM

5.6.3 Creating and managing groups

 

After creating users, you can create groups, and then assign users to them. In the following examples, we create a group, server_admins, and assign the user wilber to this group. The example server instance is named LDAP1, and the instance's suffix is dc=LDAP1,dc=COM.

Procedure 5.2: Creating LDAP groups and assigning users to them
 

  1. Create the group: 

    > sudo dsidm LDAP1 group create

    You will be prompted for a group name. Enter your chosen group name, which in the following example is SERVER_ADMINS: 

    Enter value for cn : SERVER_ADMINS

  2. Add the user wilber (created in Procedure 5.1, “Creating LDAP users”) to the group: 

    > sudo dsidm LDAP1 group add_member SERVER_ADMINS \
uid=wilber,ou=people,dc=LDAP1,dc=COM
added member: uid=wilber,ou=people,dc=LDAP1,dc=COM

5.6.4 Deleting users and groups, and removing users from groups

 

Use the dsidm command to delete users, remove users from groups, and delete groups. The following example removes our example user wilber from the server_admins group: 

> sudo dsidm LDAP1 group remove_member SERVER_ADMINS \
uid=wilber,ou=people,dc=LDAP1,dc=COM

Delete a user: 

> sudo dsidm LDAP1 user delete \
uid=wilber,ou=people,dc=LDAP1,dc=COM

Delete a group: 

> sudo dsidm LDAP1 group delete SERVER_ADMINS

5.7 Managing plug-ins

 

Use the following command to list all available plug-ins, enabled and disabled. Use your server's hostname rather than the instance name of your 389 Directory Server, like the following example hostname of LDAPSERVER1: 

> sudo dsconf -D "cn=Directory Manager" ldap://LDAPSERVER1 plugin list
Enter password for cn=Directory Manager on ldap://LDAPSERVER1: PASSWORD

7-bit check
Account Policy Plugin
Account Usability Plugin
ACL Plugin
ACL preoperation
[...]

The following command enables the MemberOf plug-in referenced in Section 5.8, “Using SSSD to manage LDAP authentication”. MemberOf simplifies user searches, by returning the user and any groups the user belongs to, with a single command. Without MemberOf, a client must run multiple lookups to find a user's group memberships. 

> sudo dsconf -D "cn=Directory Manager" ldap://LDAPSERVER1 plugin memberof enable

The plug-in names used in commands are lowercase, so they are different from how they appear when you list them. If you make a mistake with a plug-in name, you see a helpful error message: 

dsconf instance plugin: error: invalid choice: 'MemberOf' (choose from
'memberof', 'automember', 'referential-integrity', 'root-dn', 'usn',
'account-policy', 'attr-uniq', 'dna', 'linked-attr', 'managed-entries',
'pass-through-auth', 'retro-changelog', 'posix-winsync', 'contentsync', 'list',
'show', 'set')

After enabling a plug-in, it is necessary to restart the server: 

> sudo systemctl restart dirsrv@LDAPSERVER1.service

Next, configure the plug-in. The following example enables MemberOf to search all entries. Use your instance name rather than the server's hostname: 

> sudo dsconf LDAP1 plugin memberOf set --scope dc=example,dc=com
Successfully changed the cn=MemberOf Plugin,cn=plugins,cn=config

After the MemberOf plug-in is enabled and configured, all new groups and users are automatically MemberOf targets. However, any users and groups that exist before it is enabled are not. They must be marked manually: 

> sudo dsidm LDAP1 user modify suzanne add:objectclass:nsmemberof
Successfully modified uid=suzanne,ou=people,dc=ldap1,dc=com

Now suzanne information and group membership are listed with a single command: 

> sudo dsidm LDAP1 user get suzanne
dn: uid=suzanne,ou=people,dc=ldap1,dc=com
cn: suzanne
displayName: Suzanne Geeko
gidNumber: 102
homeDirectory: /home/suzanne
memberOf: cn=SERVER_ADMINS,ou=groups,dc=ldap1,dc=com

Modifying a larger number of users is a lot of work. The following example shows how to make all legacy users MemberOf targets with one fixup command: 

> sudo dsconf LDAP1 plugin memberof fixup -f '(objectClass=*)' dc=LDAP1,dc=COM

5.7.1 Unsupported plug-ins on 389 Directory Server

 

The following plug-ins are not supported on 389 Directory Server:

  • Distributed Numeric Assignment (DNA) plug-in

  • Managed Entries Plug-in (MEP)

  • Posix Winsync plug-in

5.8 Using SSSD to manage LDAP authentication

 

The System Security Services Daemon (SSSD) manages authentication, identification, and access controls for remote users. This section describes how to use SSSD to manage authentication and identification for your 389 Directory Server.

SSSD mediates between your LDAP server and clients. It supports several provider back-ends, such as LDAP, Active Directory, and Kerberos. SSSD supports services, including SSH, PAM, NSS and sudo. SSSD provides performance benefits and resilience through caching user IDs and credentials. Caching reduces the number of requests to your 389 DS server, and provides authentication and identity services when the back-ends are unavailable.

If the Name Services Caching Daemon (nscd) is running on your network, you should disable or remove it. nscd caches only the common name service requests, such as passwd, group, hosts, service and netgroup, and will conflict with SSSD.

Your LDAP server is the provider, and your SSSD instance is the client of the provider. You may install SSSD on your 389 DS server, but installing it on a separate machine provides some resilience in case the 389 DS server becomes unavailable. Use the following procedure to install and configure an SSSD client. The example 389 DS instance name is LDAP1:

  1. Install the sssd and sssd-ldap packages: 

    > sudo zypper in sssd sssd-ldap

  2. Back up the /etc/sssd/sssd.conf file, if it exists: 

    > sudo old /etc/sssd/sssd.conf

  3. Create your new SSSD configuration template. The allowed output file names are sssd.conf and ldap.conf. display sends the output to stdout. The following example creates a client configuration in /etc/sssd/sssd.conf: 

    > sudo cd /etc/sssd
> sudo dsidm LDAP1 client_config sssd.conf

  4. Review the output and make any necessary changes to suit your environment. The following /etc/sssd/sssd.conf file demonstrates a working example.

    Important
    Important: MemberOf

    The LDAP access filter relies on MemberOf being configured. For details, see Section 5.7, “Managing plug-ins”. 

    [sssd]
services = nss, pam, ssh, sudo
config_file_version = 2
domains = default

[nss]
homedir_substring = /home

[domain/default]
# If you have large groups (for example, 50+ members),
# you should set this to True
ignore_group_members = False
debug_level=3
cache_credentials = True
id_provider = ldap
auth_provider = ldap
access_provider = ldap
chpass_provider = ldap

ldap_schema = rfc2307bis
ldap_search_base = dc=example,dc=com
# We strongly recommend ldaps
ldap_uri = ldaps://ldap.example.com
ldap_tls_reqcert = demand
ldap_tls_cacert = /etc/openldap/ldap.crt
ldap_access_filter = (|(memberof=cn=<login group>,ou=Groups,dc=example,dc=com))
enumerate = false
access_provider = ldap

ldap_user_member_of = memberof
ldap_user_gecos = cn
ldap_user_uuid = nsUniqueId
ldap_group_uuid = nsUniqueId
ldap_account_expire_policy = rhds
ldap_access_order = filter, expire
# add these lines to /etc/ssh/sshd_config
#  AuthorizedKeysCommand /usr/bin/sss_ssh_authorizedkeys
#  AuthorizedKeysCommandUser nobody
ldap_user_ssh_public_key = nsSshPublicKey

  5. Set file ownership to root, and restrict read-write permissions to root: 

    > sudo chown root:root /etc/sssd/sssd.conf
> sudo chmod 600 /etc/sssd/sssd.conf

  6. Edit the /etc/nsswitch.conf configuration file on the SSSD server to include the following lines: 

    passwd: compat sss
group:  compat sss
shadow: compat sss

  7. Edit the PAM configuration on the SSSD server, modifying common-account-pc, common-auth-pc, common-password-pc, and common-session-pc. SUSE Linux Enterprise Server provides a command to modify all of these files at once, pam-config: 

    > sudo pam-config -a --sss

  8. Verify the modified configuration: 

    > sudo pam-config -q --sss
auth:
account:
password:
session:

  9. Copy /etc/dirsrv/slapd-LDAP1/ca.crt from the 389 DS server to /etc/openldap/certs on your SSSD server, then rehash it: 

    > sudo c_rehash /etc/openldap/certs

  10. Enable and start SSSD: 

    > sudo systemctl enable --now sssd

See Chapter 4, Setting up authentication clients using YaST for information on managing the sssd.service with systemctl.

5.8.1 Unsupported password hashes and authentication schemes

 

The following are not supported as configuration values in dse.ldif for the settings nsslapd-rootpwstoragescheme or passwordStorageScheme, or as a value of passwordStorageScheme in the account policy objects:

  • SHA

  • SSHA

  • SHA256

  • SSHA256

  • SHA384

  • SSHA384

  • SHA512

  • SSHA512

  • NS-MTA-MD5

  • clear

  • MD5

  • SMD5

Note
Note

Database imports that contain these values are supported if nsslapd-enable-upgrade-hash is set to on (defaults to on).

5.9 Migrating to 389 Directory Server from OpenLDAP

 

OpenLDAP is deprecated and no longer supported as of SUSE Linux Enterprise 15 SP3. It has been replaced by 389 Directory Server. SUSE provides the openldap_to_ds utility to assist with migration, included in the 389-ds package.

The openldap_to_ds utility automates as much of the migration as possible. However, every LDAP deployment is different, and it is impossible to develop a tool that satisfies all situations. When necessary, intervene and perform manual steps. Additionally, test your migration procedure thoroughly before attempting a production migration.

Important
Important: Read the help page

Before using the openldap_to_ds migration tool, we strongly recommend reading the output of openldap_to_ds --help. It helps you learn about the capabilities and limitations of the migration tool, and prevents you from making wrong assumptions.

5.9.1 Testing migration from OpenLDAP

 

Due to significant differences between OpenLDAP and 389 Directory Server, migration involves repeated testing and adjustments. It is helpful to do a quick migration test to get an idea of what steps are necessary for a successful migration.

Prerequisites:

  • A running 389 Directory Server instance

  • An OpenLDAP slapd configuration file or directory in dynamic ldif format

  • An ldif file backup of your OpenLDAP database

If your slapd configuration is not in dynamic ldif format, create a dynamic copy with slaptest. Create a slapd.d directory, for example /root/slapd.d/, then run the following command: 

> sudo slaptest -f /etc/openldap/slapd.conf -F /root/slapd.d

This results in several files similar to the following example: 

> sudo ls /root/slapd.d/*

/root/slapd.d/cn=config.ldif

/root/slapd.d/cn=config:
cn=module{0}.ldif  cn=schema.ldif                 olcDatabase={0}config.ldif
cn=schema          olcDatabase={-1}frontend.ldif  olcDatabase={1}mdb.ldif

Create one ldif file per suffix. In the following examples, the suffix is dc=LDAP1,dc=COM. If you are using the /etc/openldap/slapd.conf format, use the following command to create the ldif backup file: 

> sudo slapcat -f /etc/openldap/slapd.conf -b dc=LDAP1,dc=COM \
-l /root/LDAP1-COM.ldif

Use openldap_to_ds to analyze the configuration and files, and show a migration plan without changing anything: 

> sudo openldap_to_ds LDAP1\
/root/slapd.d /root/LDAP1-COM.ldif.ldif

This performs a dry run and does not change anything. The output looks like this: 

Examining OpenLDAP Configuration ...
Completed OpenLDAP Configuration Parsing.
Examining Ldifs ...
Completed Ldif Metadata Parsing.
The following migration steps will be performed:
 * Schema Skip Unsupported Attribute -> otherMailbox (0.9.2342.19200300.100.1.22)
 * Schema Skip Unsupported Attribute -> dSAQuality (0.9.2342.19200300.100.1.49)
 * Schema Skip Unsupported Attribute -> singleLevelQuality (0.9.2342.19200300.100.1.50)
 * Schema Skip Unsupported Attribute -> subtreeMinimumQuality (0.9.2342.19200300.100.1.51)
 * Schema Skip Unsupported Attribute -> subtreeMaximumQuality (0.9.2342.19200300.100.1.52)
 * Schema Create Attribute -> suseDefaultBase (SUSE.YaST.ModuleConfig.Attr:2)
 * Schema Create Attribute -> suseNextUniqueId (SUSE.YaST.ModuleConfig.Attr:3)
[...]
 * Schema Create ObjectClass -> suseDhcpConfiguration (SUSE.YaST.ModuleConfig.OC:10)
 * Schema Create ObjectClass -> suseMailConfiguration (SUSE.YaST.ModuleConfig.OC:11)
 * Database Reindex -> dc=example,dc=com
 * Database Import Ldif -> dc=example,dc=com from example.ldif -
excluding entry attributes = [{'structuralobjectclass', 'entrycsn'}]
No actions taken. To apply migration plan, use '--confirm'

The following example performs the migration, and the output looks different from the dry run: 

  > sudo openldap_to_ds LDAP1 /root/slapd.d /root/LDAP1-COM.ldif --confirm
Starting Migration ... This may take some time ...
migration: 1 / 40 complete ...
migration: 2 / 40 complete ...
migration: 3 / 40 complete ...
[...]
Index task index_all_05252021_120216 completed successfully
post: 39 / 40 complete ...
post: 40 / 40 complete ...
🎉 Migration complete!
----------------------
You should now review your instance configuration and data:
 * [ ] - Create/Migrate Database Access Controls (ACI)
 * [ ] - Enable and Verify TLS (LDAPS) Operation
 * [ ] - Schedule Automatic Backups
 * [ ] - Verify Accounts Can Bind Correctly
 * [ ] - Review Schema Inconistent ObjectClass -> pilotOrganization (0.9.2342.19200300.100.4.20)
 * [ ] - Review Database Imported Content is Correct -> dc=ldap1,dc=com

When the migration is complete, openldap_to_ds creates a checklist of post-migration tasks that must be completed. It is a best practice to document your post-migration steps, so that you can reproduce them in your post-production procedures. Then test clients and application integrations to the migrated 389 Directory Server instance.

Important
Important: Develop a rollback plan

Develop a rollback plan in case of any failures. This plan should define a successful migration, the tests to determine what worked and what needs to be fixed, which steps are critical, what can be deferred until later, how to decide when to undo any changes, how to undo them with minimal disruption, and which other teams need to be involved.

Due to the variability of deployments, it is difficult to provide a recipe for a successful production migration. After you have thoroughly tested the migration process and verified that you get good results, the following general steps help:

  • Lower all hostname/DNS TTLs to 5 minutes 48 hours before the change, to allow a fast rollback to your existing OpenLDAP deployment.

  • Pause all data synchronization and incoming data processes, so that the data in the OpenLDAP environment does not change during the migration.

  • Have all 389 Directory Server hosts ready for deployment before the migration.

  • Have your test migration documentation available.

5.9.2 Testing migration of OpenLDAP servers that use saslauthd

 

In OpenLDAP deployments, it is common to use saslauthd for passthrough authentication of users. The authentication process involves the following components: 

 ┌─────────────────┐
 │                 │
 │   LDAP client   │
 │                 │
 └─────────────────┘
          │
      binds to
          │
          ▼
 ┌─────────────────┐
 │    OpenLDAP     │
 │     server      │
 │                 │
 └─────────────────┘
          │
          │
          ▼
 ┌─────────────────┐
 │                 │
 │    saslauthd    │
 │                 │
 └─────────────────┘
          │
          │
          ▼
 ┌─────────────────┐
 │                 │
 │  External auth  │
 │                 │
 └─────────────────┘

For checking the correctness of configuration and subsequent troubleshooting, the following information is important:

  • OpenLDAP discovers that a user is allowed passthrough authentication if the userPassword attribute has a value with the userPassword: {SASL}USERNAME@REALM format. The prerequisite is to build the OpenLDAP server with the --enable-spasswd option to enable passthrough authentication.

  • OpenLDAP configures its connection to saslauthd from /usr/lib/sasl2/slapd.conf.

  • saslauthd discovers the relevant modules using its command-line parameters configured in /etc/sysconfig/saslauthd.

  • The back-end modules of saslauthd use their own configuration, as documented in man saslauthd.

Detailed information about passthrough authentication using OpenLDAP is available in the official OpenLDAP Admin Guide.

5.9.2.1 Migrating SASL passthrough authentication from OpenLDAP to 389 Directory Server

 

As a best practice for correctly migrating SASL passthrough authentication from OpenLDAP to 389 Directory Server, refer to the following steps:

  1. Before migration, ensure that you can successfully run testsaslauthd on the OpenLDAP server. 

    > sudo testsaslauthd -u USERNAME@REALM -p PASSWORD

    The realm routes the authentication to the correct back-end in saslauthd, and the user name is then used to check the identity.

  2. Install the pam_saslauthd package that enables 389 Directory Server to connect with saslauthd. 

    > sudo zypper install -y pam_saslauthd

  3. Migrate from OpenLDAP to 389 Directory Server by running the openldap_to_ds command-line tool. For detailed information on the migration process, refer to the section Section 5.9.1, “Testing migration from OpenLDAP”.

    Note
    Note

    While the openldap_to_ds process is running, if a user is detected as having the value of the userPssword attribute in the userPassword: {SASL}USERNAME@REALM format, it is removed and placed as the value of the nsSaslauthId attribute in the nsSaslauthId: USERNAME@REALM format. Additionally, the attribute value objectClass: nsSaslauthAccount is automatically added to support the modification.

  4. After completion of the migration, check whether the PAM passthrough authentication is configured correctly by running the following commands: 

    > sudo dsconf INSTANCE plugin pam-pass-through-auth show
    > sudo dsconf INSTANCE plugin pam-pass-through-auth list

After successful migration, the passthrough authentication flow involves the following components: 

  ┌─────────────────┐
  │                 │
  │   LDAP client   │
  │                 │
  └─────────────────┘
           │
       binds to
           │
           ▼
  ┌─────────────────┐
  │     389-DS      │
  │     server      │
  │                 │
  └─────────────────┘
           │
           ▼
  ┌─────────────────┐
  │                 │
  │  pam saslauthd  │
  │                 │
  └─────────────────┘
           │
           ▼
  ┌─────────────────┐
  │                 │
  │    saslauthd    │
  │                 │
  └─────────────────┘
           │
           │
           ▼
  ┌─────────────────┐
  │                 │
  │  External auth  │
  │                 │
  └─────────────────┘

5.9.2.2 Troubleshooting saslauthd passthrough authentication

 

To troubleshoot problems with saslauthd passthrough authentication before and after the migration from OpenLDAP to 389 Directory Server, refer to the following tips:

Ensure that testsaslauthd works with USERNAME@REALM.

Refer to the step for running testsaslauthd in the Section 5.9.2, “Testing migration of OpenLDAP servers that use saslauthd” section.

In case of problems, try the following:

  • Check /etc/sysconfig/saslauthd to ensure the saslauthd back-end modules are configured correctly. For detailed information on the back-end modules of saslauthd and their configurations, run man saslauthd.

  • Turn on debug logging by adding SASLAUTHD_PARAMS="-d" in /etc/sysconfig/saslauthd.

  • View the saslauthd logs that are available as part of the output of journalctl.

Ensure that PAM saslauthd works correctly.

To check if PAM saslauthd works correctly, you can use the pam_tester tool available at https://github.com/kanidm/pam_tester.

Note
Note

The pam_tester tool is NOT officially supported.

Ensure that the PAM Pass Through Auth plug-in is enabled.

Check the status of the PAM Pass Through Auth plug-in by running the following command: 

> sudo dsconf INSTANCE plugin pam-pass-through-auth status

To enable the plug-in, run the following command: 

> sudo dsconf INSTANCE plugin pam-pass-through-auth enable
Check the configuration of the PAM Pass Through Auth plug-in.

To check the configuration of the PAM Pass Through Auth plug-in for the server instance, run the following command: 

> sudo dsconf INSTANCE plugin pam-pass-through-auth show
Check the error logs for the user of the server instance.

Check the logs available in /var/lib/SERVER_USER_NAME/INSTANCE/error.

5.9.3 Planning your migration

 

As OpenLDAP is a “box of parts” and highly customizable, it is not possible to prescribe a “one size fits all” migration. It is necessary to assess your current environment and configuration with OpenLDAP and other integrations. This includes, and is not limited to:

  • Replication topology

  • High availability and load balancer configurations

  • External data flows (IGA, HR, AD, etc.)

  • Configured overlays (plug-ins in 389 Directory Server)

  • Client configuration and expected server features

  • Customized schema

  • TLS configuration

Plan what your 389 Directory Server deployment will look like in the end. This includes the same list, except replace overlays with plug-ins. Once you have assessed your current environment and planned what your 389 Directory Server environment will look like, you can then form a migration plan. We recommended building the 389 Directory Server environment in parallel to your OpenLDAP environment to allow switching between them.

Migrating from OpenLDAP to 389 Directory Server is a one-way migration. There are enough differences between the two that they cannot interoperate, and there is not a migration path from 389 Directory Server to OpenLDAP. The following table highlights the major similarities and differences.

FeatureOpenLDAP389 Directory ServerCompatible
Two-way replicationSyncREPL389 DS-specific systemNo
MemberOfOverlayPlug-inYes, simple configurations only
External AuthProxy-No
Active Directory Synchronization-Winsync Plug-inNo
Inbuilt SchemaOLDAP Schemas389 SchemasYes, supported by migration tool
Custom SchemaOLDAP Schemas389 SchemasYes, supported by migration tool
Database ImportLDIFLDIFYes, supported by migration tool
Password hashesVariesVariesYes, all formats supported excluding Argon2
OpenLDAP to 389 DS replication--No mechanism to replicate to 389 DS is possible
Time-based one-time password (TOTP)TOTP overlay-No, currently not supported
entryUUIDPart of OpenLDAPPlug-inYes

5.10 Importing TLS server certificates and keys

 

You can manage your CA certificates and keys for 389 Directory Server with the following command line tools: certutil, openssl, and pk12util.

For testing purposes, you can use the self-signed certificate that dscreate creates when you create a new 389 DS instance. Find the certificate at /etc/dirsrv/slapd-INSTANCE-NAME/ca.crt.

For production environments, it is a best practice to use a third-party certificate authority, such as Let's Encrypt, CAcert.org, SSL.com, or whatever CA you choose. Request a server certificate, a client certificate, and a root certificate.

Important
Important

The Mozilla NSS (Network Security Services) toolkit uses nicknames for certificates in the certificate store. The server certificate uses the nickname Server-Cert.

  1. Use the following commands to remove the Self-Signed-CA and Server-Cert from the instance: 

    > sudo dsctl INSTANCE_NAME tls remove-cert Self-Signed-CA
> sudo dsctl INSTANCE_NAME tls remove-cert Server-Cert

    Replace INSTANCE_NAME with the instance name of the directory server. This is LDAP1 in the previous sections.

  2. Import the CA that has signed your certificate. 

    > sudo sudo dsctl INSTANCE_NAME tls import-ca
   /path/to/CA/in/PEM/format/CA.pem  NICKNAME_FOR_CA

    Replace INSTANCE_NAME with the instance name of the directory server. Replace /path/to/CA/in/PEM/format/CA.pem with the full path to the CA certificate file in PEM format. Replace NICKNAME_FOR_CA with a nickname for the CA.

  3. Import the server certificate and the key for the certificate. 

    > sudo dsctl INSTANCE_NAME tls import-server-key-cert
  /path/to/SERVER.pem /path/to/SERVER.key

    Replace INSTANCE_NAME with the instance name of the directory server. Replace /path/to/SERVER.pem with the full path to the server certificate in PEM format. Replace /path/to/SERVER.key with the full path to the server certificate key file in PEM format.

  4. Restart the instance so that the new certificates are used. 

    > sudo systemctl restart dirsrv@INSTANCE-NAME..service

    Replace INSTANCE_NAME with the instance name of the directory server.

5.11 Setting up replication

 

389 Directory Server supports replicating its database content between multiple servers. According to the type of replication, this provides:

  • Faster performance and response times

  • Fault tolerance and failover

  • Load balancing

  • High availability

A database is the smallest unit of a directory that can be replicated. You can replicate an entire database, but not a subtree within a database. One database must correspond to one suffix. You cannot replicate a suffix that is distributed over two or more databases.

A replica that sends data to another replica is a supplier. A replica that receives data from a supplier is a consumer. Replication is always initiated by the supplier, and a single supplier can send data to multiple consumers. The supplier is a read-write replica, and the consumer is read-only, except in the case of multi-supplier replication. In multi-supplier replication the suppliers are both suppliers and consumers of the same data.

5.11.1 Asynchronous writes

 

389 DS manages replication differently than other databases. Replication is asynchronous, and eventually consistent. This means:

  • Any write or change to a single server is immediately accepted.

  • There is a delay between a write finishing on one server, and then replicating and being visible on other servers.

  • If that write conflicts with writes on other servers, it may be rolled back at some point in the future.

  • Not all servers may show identical content at the same time due to replication delay.

As LDAP is “low-write,” these factors mean that all servers are at least up to a common baseline of a known consistent state. Small changes occur on top of this baseline, so many of these aspects of delayed replication are not perceived in day to day usage.

5.11.2 Designing your topology

 

Consider the following factors when you are designing your replication topology.

  • The need for replication: high availability, geo-location, read scaling, or a combination of all.

  • How many replicas (nodes, servers) you plan to have in your topology.

  • Direction of data flows, both inside of the topology, and data flowing into the topology.

  • How clients balance across nodes of the topology for their requests (multiple ldap URIs, SRV records, load balancers).

These factors all affect how you may create your topology. (See Section 5.11.3, “Example replication topologies” for topology examples.)

5.11.3 Example replication topologies

 

The following sections provide examples of replication topologies, using two to six 389 Directory Server nodes. The maximum number of supported supplier replicas in a topology is 20. Operational experience shows the optimal number for replication efficiency is a maximum of eight.

5.11.3.1 Two replicas

 
Example 5.4: Two supplier replicas
 
┌────┐       ┌────┐
│ S1 │◀─────▶│ S2 │
└────┘       └────┘

In Example 5.4, “Two supplier replicas” there are two replicas, S1 and S2, which replicate bi-directionally between each other, so they are both suppliers and consumers. S1 and S2 could be in separate data centers, or in the same data center. Clients can balance across the servers using LDAP URIs, a load balancer, or DNS SRV records. This is the simplest topology for high availability. Each server needs to be able to provide 100% of client load, in case the other server is offline for any reason. A two-node replication is generally not adequate for horizontal read scaling, as a single node handles all read requests if the other node is offline.

Note
Note: Default topology

The two-node topology should be considered the default topology, because it is the simplest to manage. You can expand your topology over time, as necessary.

5.11.3.2 Four supplier replicas

 
Example 5.5: Four supplier replicas
 
┌────┐       ┌────┐
│ S1 │◀─────▶│ S2 │
└────┘       └────┘
   ▲            ▲
   │            │
   ▼            ▼
┌────┐       ┌────┐
│ S3 │◀─────▶│ S4 │
└────┘       └────┘

Example 5.5, “Four supplier replicas” has four supplier replicas, which all synchronize to each other. These could be in four datacenters, or two servers per datacenter. In the case of one node per data center, each node should be able to support 100% of client load. When there are two per datacenter, each one only needs to scale to 50% of the client load.

5.11.3.3 Six replicas

 
Example 5.6: Six replicas
 
                  ┌────┐       ┌────┐
                  │ S1 │◀─────▶│ S2 │
                  └────┘       └────┘
                     ▲            ▲
                     │            │
   ┌────────────┬────┴────────────┴─────┬────────────┐
   │            │                       │            │
   ▼            ▼                       ▼            ▼
┌────┐       ┌────┐                  ┌────┐       ┌────┐
│ S3 │◀─────▶│ S4 │                  │ S5 │◀─────▶│ S6 │
└────┘       └────┘                  └────┘       └────┘

In Example 5.6, “Six replicas”, each pair is in a separate location. S1 and S2 are the suppliers, and S3, S4, S5, and S6 are consumers of S1 and S2. Each pair of servers replicate to each other. S3, S4, S5 and S6 can accept writes, though most of the replication is done through S1 and S2. This setup provides geographic separation for high availability and scaling.

5.11.3.4 Six replicas with read-only consumers

 
Example 5.7: Six replicas with read-only consumers
 
             ┌────┐       ┌────┐
             │ S1 │◀─────▶│ S2 │
             └────┘       └────┘
                │            │
                │            │
   ┌────────────┼────────────┼────────────┐
   │            │            │            │
   ▼            ▼            ▼            ▼
┌────┐       ┌────┐       ┌────┐       ┌────┐
│ S3 │       │ S4 │       │ S5 │       │ S6 │
└────┘       └────┘       └────┘       └────┘

In Example 5.7, “Six replicas with read-only consumers”, S1 and S2 are the suppliers, and the other four servers are read-only consumers. All changes occur on S1 and S2, and are propagated to the four replicas. Read-only consumers can be configured to store only a subset of the database, or partial entries, to limit data exposure. You could have a fractional read-only server in a DMZ, for example, so that if data is exposed, changes can not propagate back to the other replicas.

5.11.4 Terminology

 

In the example topologies we have seen that 389 DS can take on a number of roles in a topology. The following list clarifies the terminology.

Replica

An instance of 389 DS with an attached database.

Read-write replica

A replica with a full copy of a database, that accepts read and write operations.

Read-only replica

A replica with a full copy of a database, that only accepts read operations.

Fractional read-only replica

A replica with a partial copy of a database, that only accepts read- only operations.

Supplier

A replica that supplies data from its database to another replica.

Consumer

A replica that receives data from another replica to write into its database.

Replication agreement

The configuration of a server defining its supplier and consumer relation to another replica.

Topology

A set of replicas connected via replication agreements.

Replica ID

A unique identifier of the 389 Directory Server instance within the replication topology.

Replication manager

An account with replication rights in the directory.

5.11.5 Configuring replication

 

The first example sets up a two node bi-directional replication with a single read-only server, as a minimal starting example. In the following examples, the host names of the two read-write nodes are RW1 and RW2, and the read-only server is RO1. (Use your own host names.)

All servers should have a back-end with an identical suffix. Only one server, RW1, needs an initial copy of the database.

5.11.5.1 Configuring two-node replication

 

The following commands configure the read-write replicas in a two-node setup (Example 5.4, “Two supplier replicas”), with the host names RW1 and RW2. (Use your own host names.)

Warning
Warning: Create a strong replication manager password

The replication manager should be considered equivalent to the directory manager in terms of security and access, and should have a strong password.

If you create different replication manager passwords for each server, be sure to keep track of which password belongs to which server. For example, when you configure the outbound connection in RW1's replication agreement, you need to set the replication manager password to the RW2 replication manager password.

First, configure RW1: 

> sudo dsconf INSTANCE-NAME replication create-manager
> sudo dsconf INSTANCE-NAME replication enable \
--suffix dc=example,dc=com \
--role supplier --replica-id 1 --bind-dn "cn=replication manager,cn=config"

Configure RW2: 

> sudo dsconf INSTANCE-NAME replication create-manager
> sudo dsconf INSTANCE-NAME replication enable \
--suffix dc=example,dc=com \
--role supplier --replica-id 2 --bind-dn "cn=replication manager,cn=config"

This will create the replication metadata required on RW1 and RW2. Note the difference in the replica-id between the two servers. This also creates the replication manager account, which is an account with replication rights for authenticating between the two nodes.

RW1 and RW2 are now both configured to have replication metadata. The next step is to create the first agreement for outbound data from RW1 to RW2. 

> sudo dsconf INSTANCE-NAME repl-agmt create \
--suffix dc=example,dc=com \
--host=RW2 --port=636 --conn-protocol LDAPS --bind-dn "cn=replication manager,cn=config" \
--bind-passwd PASSWORD --bind-method SIMPLE RW1_to_RW2

Data does not flow from RW1 to RW2 until after a full synchronization of the database, which is called an initialization or reinit. This resets all database content on RW2 to match the content of RW1. Run the following command to trigger a reinit of the data: 

> sudo dsconf INSTANCE-NAME repl-agmt init \
--suffix dc=example,dc=com RW1_to_RW2

Check the status by running this command on RW1: 

> sudo dsconf INSTANCE-NAME repl-agmt init-status \
--suffix dc=example,dc=com RW1_to_RW2

When it is finished, you should see an Agreement successfully initialized message. If you get an error message, check the errors log. Otherwise, you should see the identical content from RW1 on RW2.

Finally, to make this bi-directional, configure a replication agreement from RW2 outbound to RW1: 

> sudo dsconf INSTANCE-NAME repl-agmt create \
--suffix dc=example,dc=com \
--host=RW1 --port=636 --conn-protocol LDAPS \
--bind-dn "cn=replication manager,cn=config" --bind-passwd PASSWORD \
--bind-method SIMPLE RW2_to_RW1

Changes made on either RW1 or RW2 are now replicated to the other. Check replication status on either server with the following command: 

> sudo dsconf INSTANCE-NAME repl-agmt status \
--suffix dc=example,dc=com \
--bind-dn "cn=replication manager,cn=config" \
--bind-passwd PASSWORD RW2_to_RW1

5.11.5.2 Configuring a read-only node

 

To create a read-only node, start by creating the replication manager account and metadata. The hostname of the example server is RO3:

Warning
Warning: Create a strong replication manager password

The replication manager should be considered equivalent to the directory manager in terms of security and access, and should have a strong password.

If you create different replication manager passwords for each server, be sure to keep track of which password belongs to which server. For example, when you configure the outbound connection in RW1's replication agreement, you need to set the replication manager password to the RW2 replication manager password. 

> sudo dsconf INSTANCE_NAME replication create-manager
> sudo  dsconf INSTANCE_NAME \
replication enable --suffix dc=EXAMPLE,dc=COM \
--role consumer --bind-dn "cn=replication manager,cn=config"

For a read-only replica, you do not provide a replica-id, and the role is set to consumer. This allocates a special read-only replica-id for all read-only replicas. After the read-only replica is created, add the replication agreements from RW1 and RW2 to the read-only instance. The following example is on RW1: 

> sudo dsconf INSTANCE_NAME \
repl-agmt create --suffix dc=EXAMPLE,dc=COM \
--host=RO3 --port=636 --conn-protocol LDAPS \
--bind-dn "cn=replication manager,cn=config" --bind-passwd PASSWORD
--bind-method SIMPLE RW1_to_RO3

The following example, on RW2, configures the replication agreement between RW2 and RO3: 

> sudo dsconf INSTANCE_NAME repl-agmt create \
--suffix dc=EXAMPLE,dc=COM \
--host=RO3 --port=636 --conn-protocol LDAPS \
--bind-dn "cn=replication manager,cn=config" --bind-passwd PASSWORD \
--bind-method SIMPLE RW2_to_RO3

After these steps are completed, you can use either RW1 or RW2 to perform the initialization of the database on RO3. The following example initializes RO3 from RW2: 

> sudo dsconf INSTANCE_NAME repl-agmt init
--suffix dc=EXAMPLE,dc=COM RW2_to_RO3

5.11.6 Monitoring and healthcheck

 

The dsconf command includes a monitoring option. You can check the status of each replica status directly on the replicas, or from other hosts. The following example commands are run on RW1, checking the status on two remote replicas, and then on itself: 

> sudo dsconf -D "cn=Directory Manager" ldap://RW2 replication monitor
> sudo dsconf -D "cn=Directory Manager" ldap://RO3 replication monitor
> sudo dsconf -D "cn=Directory Manager" ldap://RW1 replication monitor

The dsctl command has a healthcheck option. The following example runs a replication healthcheck on the local 389 DS instance: 

> sudo dsctl INSTANCE_NAME healthcheck --check replication

Use the -v option for verbosity, to see what the healthcheck examines: 

> sudo dsctl -v INSTANCE_NAME healthcheck --check replication

Run dsctl INSTANCE_NAME healthcheck with no options for a general health check.

Run the following command to see a list of the checks that healthcheck performs: 

> sudo dsctl INSTANCE_NAME healthcheck --list-checks
config:hr_timestamp
config:passwordscheme
backends:userroot:cl_trimming
backends:userroot:mappingtree
backends:userroot:search
backends:userroot:virt_attrs
encryption:check_tls_version
fschecks:file_perms
[...]

You can run one or more of the individual checks: 

> sudo dsctl INSTANCE_NAME healthcheck \
--check monitor-disk-space:disk_space tls:certificate_expiration

5.11.7 Making backups

 

When replication is enabled, you need to adjust your 389 Directory Server backup strategy (see Section 5.5, “Backing up and restoring 389 Directory Server” to learn about making backups). If you are using db2ldif, you must add the --replication flag to ensure that replication metadata is backed up. You should backup all servers in the topology. When restoring from backup, start by restoring a single node of the topology, then reinitialize all other nodes as new instances.

5.11.8 Pausing and resuming replication

 

You can pause replication during maintenance windows, or anytime you need to stop it. A node of the topology can only be offline for a maximum of days up to the limit of the changelog (see Section 5.11.9, “ Changelog max-age”).

Use the repl-agmt command to pause replication. The following example is on RW2: 

> sudo dsconf INSTANCE_NAME repl-agmt disable \
--suffix dc=EXAMPLE,dc=COM RW2_to_RW1

The following example re-enables replication: 

> sudo dsconf INSTANCE_NAME repl-agmt enable \
--suffix dc=EXAMPLE,dc=COM RW2_to_RW1

5.11.9 Changelog max-age

 

A replica can be offline for up to the length of time defined by the changelog max-age option. max-age defines the maximum age of any entry in the changelog. Any items older than the max-age value are automatically removed.

After the replica comes back online, it synchronizes with the other replicas. If it is offline for longer than the max-age value, the replica needs to be re-initialized and refuses to accept or provide changes to other nodes, as they may be inconsistent. The following example sets the max-age to seven days: 

> sudo dsconf INSTANCE_NAME \
replication set-changelog --max-age 7d \
--suffix dc=EXAMPLE,dc=COM

5.11.10 Removing a replica

 

To remove a replica, first fence the node to prevent any incoming changes or reads. Then, find all servers that have incoming replication agreements with the node you are removing, and remove them. The following example removes RW2. Start by disabling the outbound replication agreement on RW1: 

> sudo dsconf INSTANCE_NAME repl-agmt delete \
--suffix dc=EXAMPLE,dc=COM RW1_to_RW2

On the replica you are removing, which in the following example is RW2, remove all outbound agreements: 

> sudo dsconf INSTANCE_NAME repl-agmt delete \
--suffix dc=EXAMPLE,dc=COM RW2_to_RW1
> sudo dsconf INSTANCE_NAME repl-agmt delete \
--suffix dc=EXAMPLE,dc=COM RW2_to_RO3

Stop the instance on RW2: 

> sudo systemctl stop dirsrv@INSTANCE_NAME.service

Then run the cleanallruv command to remove the replica ID from the topology. The following example is run on RW1: 

> sudo dsconf INSTANCE_NAME repl-tasks cleanallruv \
--suffix dc=EXAMPLE,dc=COM --replica-id 2
> sudo dsconf INSTANCE_NAME repl-tasks list-cleanruv-tasks

5.11.11 Limitations on replication of 389 Directory Server

 

The use of 389 Directory Server is supported within the following replication limits:

  • A maximum of 8 read-write nodes

  • A maximum of 20 replication hubs

  • A maximum of 100 read-only servers

  • A maximum of 1 Winsync Active Directory consumer as a read-write node member

5.12 Synchronizing with Microsoft Active Directory

 

389 Directory Server supports synchronizing certain user and group content from Microsoft's Active Directory, so that Linux clients can use 389 DS for their identity information without the normally required domain join process. This also allows 389 DS to extend and use its other features with the data synchronized from Active Directory.

5.12.1 Planning your synchronization topology

 

Due to how the synchronization works, only a single 389 Directory Server and Active Directory server are involved. The Active Directory server must be a full Domain Controller, and not a Read Only Domain Controller (RODC). The Global Catalog is not required on the DC that is synchronized, as 389 DS only replicates the content of a single forest in a domain.

You must first choose the direction of your data flow. There are three options: from AD to 389 DS, from 389 DS to AD, or bi- directional.

Note
Note: No password synchronization

Passwords cannot be synchronized between 389 DS and Active Directory. This may change in the future, to support Active Directory to 389 DS password flow.

Your topology looks like the following diagram. The 389 Directory Server and Active Directory topologies may differ, but the most important factor is to have only a single connection between 389 DS and Active Directory. It is important to account for this in your disaster recovery and backup plans for both 389 DS and AD, to ensure that you correctly restore only a single replication connection between these topologies. 

┌────────┐     ┌────────┐         ┌────────┐     ┌────────┐
│        │     │        │         │        │     │        │
│ 389-ds │◀───▶│ 389-ds │◀ ─ ─ ─ ▶│   AD   │◀───▶│   AD   │
│        │     │        │         │        │     │        │
└────────┘     └────────┘         └────────┘     └────────┘
    ▲               ▲                  ▲             ▲
    │               │                  │             │
    ▼               ▼                  ▼             ▼
┌────────┐     ┌────────┐         ┌────────┐     ┌────────┐
│        │     │        │         │        │     │        │
│ 389-ds │◀───▶│ 389-ds │         │   AD   │◀───▶│   AD   │
│        │     │        │         │        │     │        │
└────────┘     └────────┘         └────────┘     └────────┘

5.12.2 Prerequisites for Active Directory

 

A security group that is granted the Replicating Directory Changes permission is required. For example, you have created a group named Directory Server Sync. Follow the steps in the How to grant the 'Replicating Directory Changes' permission for the Microsoft Metadirectory Services ADMA service account (https://docs.microsoft.com/en-US/troubleshoot/windows-server/windows-security/grant-replicating-directory-changes-permission-adma-service to set this up.

Warning
Warning: Strong security needed

You should consider members of this group to be of equivalent security importance to Domain Administrators. Members of this group have the ability to read sensitive content from the Active Directory environment, so you should use strong, randomly generated service account passwords for these accounts, and carefully audit membership to this group.

You should also create a service account that is a member of this group.

Your Active Directory environment must have certificates configured for LDAPS to ensure that authentication between 389 DS and AD is secure. Authentication with Generic Security Services API/Kerberos (GSSAPI/KRB) cannot be used.

5.12.3 Prerequisites for 389 Directory Server

 

The 389 Directory Server must have a back-end database already configured with Organization Units (OUs) for entries to be synchronized into.

The 389 Directory Server must have a replica ID configured as though the server is a read-write replica. (For details about setting up replication see Section 5.11, “Setting up replication”).

5.12.4 Creating an agreement from Active Directory to 389 Directory Server

 

The following example command, which is run on the 389 Directory Server, creates a replication agreement from Active Directory to 389 Directory Server: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt create --suffix dc=example,dc=com \
  --host AD-HOSTNAME --port 636 --conn-protocol LDAPS \
  --bind-dn "cn=SERVICE-ACCOUNT,cn=USERS,dc=AD,dc=EXAMPLE,dc=COM" \
  --bind-passwd "PASSWORD" --win-subtree "cn=USERS,dc=AD,dc=EXAMPLE,dc=COM" \
  --ds-subtree ou=AD,dc=EXAMPLE,dc=COM --one-way-sync fromWindows \
  --sync-users=on --sync-groups=on --move-action delete \
  --win-domain AD-DOMAIN adsync_agreement

Once the agreement has been created, you must perform an initial resynchronization: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt init --suffix dc=example,dc=com adsync_agreement

Use the following command to check the status of the initialization: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt init-status --suffix dc=example,dc=com adsync_agreement
Note
Note: Some entries are not synchronized

In some cases, an entry may not be synchronized, even if the init status reports success. Check your 389 DS log files in /var/log/dirsrv/slapd-INSTANCE-NAME/errors.

Check the status of the agreement with the following command: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt status --suffix dc=example,dc=com adsync_agreement

Whe you are performing maintenance on the Active Directory or 389 Directory Server topology, you can pause the agreement with the following command: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt disable --suffix dc=example,dc=com adsync_agreement

Resume the agreement with the following command: 

> sudo dsconf INSTANCE-NAME repl-winsync-agmt enable --suffix dc=example,dc=com adsync_agreement

5.13 More information

 

For more information about 389 Directory Server, see: