5 LDAP with 389 Directory Server #

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:

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

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.

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

> dsctl -l
slapd-LDAP1

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. All of 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:

> 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:

> 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 some 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 some 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

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 Book “Reference”, Chapter 10 “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

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 5.5, “Managing LDAP users and groups”).

# /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

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.

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: 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:

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

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

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

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.

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.

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

There are enough differences between OpenLDAP and 389 Directory Server that migration will probably involve repeated testing and adjustments. It can be helpful to do a quick migration test to get an idea of what steps will be necessary for a successful migration.

Prerequisites:

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 all of 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: Develop a rollback plan

It is essential to 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. Once you have thoroughly tested the migration process and verified that you will get good results, there are some general steps that will help:

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:

Plan what your 389 Directory Server deployment will look like in the end. This includes the same list, except replace overlays with plugins. 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.

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

In general, 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.

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

These factors all affect how you may create your topology. (See Section 5.10.3, “Example replication topologies” for some topology examples.)

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.

5.10.3.1 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. Note that 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 will handle all read requests if the other node is offline.

Note: Default topology

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

┌────┐       ┌────┐
│ S1 │◀─────▶│ S2 │
└────┘       └────┘
   ▲            ▲
   │            │
   ▼            ▼
┌────┐       ┌────┐
│ S3 │◀─────▶│ S4 │
└────┘       └────┘

                  ┌────┐       ┌────┐
                  │ S1 │◀─────▶│ S2 │
                  └────┘       └────┘
                     ▲            ▲
                     │            │
   ┌────────────┬────┴────────────┴─────┬────────────┐
   │            │                       │            │
   ▼            ▼                       ▼            ▼
┌────┐       ┌────┐                  ┌────┐       ┌────┐
│ S3 │◀─────▶│ S4 │                  │ S5 │◀─────▶│ S6 │
└────┘       └────┘                  └────┘       └────┘

             ┌────┐       ┌────┐
             │ S1 │◀─────▶│ S2 │
             └────┘       └────┘
                │            │
                │            │
   ┌────────────┼────────────┼────────────┐
   │            │            │            │
   ▼            ▼            ▼            ▼
┌────┐       ┌────┐       ┌────┐       ┌────┐
│ S3 │       │ S4 │       │ S5 │       │ S6 │
└────┘       └────┘       └────┘       └────┘

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.

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. (Of course you must use your own host names.)

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

5.10.5.1 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 hostnames RW1 and RW2. (Remember to use your own hostnames.)

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 very 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 will not flow from RW1 to RW2 until after a full synchronization of the database, which is called an initialization or reinit. This will reset 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 will now be 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

5.10.5.2 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: 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 very 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"

Note that 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 initalizes RO3 from RW2:

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

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

When replication is enabled, you need to adjust your 389 Directory Server backup strategy (see Section 5.4, “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.

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 5.10.9, “ 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

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 will synchronize with the other replicas. If it is offline for longer than the max-age value, the replica will need to be re-initialised, and will refuse 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

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

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

Note: No password synchronization

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

Your topology will look 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 very 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   │
│        │     │        │         │        │     │        │
└────────┘     └────────┘         └────────┘     └────────┘

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: 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.

The 389 Directory Server must have a backend database already configured with Organization Units (OUs) for entries to be synchronised 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 5.10, “Setting up replication”).

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: 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