1. Administration#

1.1. Admin overview#


Simplified overview of the ID Connector#

The ID Connector replication system is composed of four components:

  1. An LDAP server containing user data.

  2. A process on the data source UCS server, receiving user creation/modification/deletion events from the LDAP server and relaying them to multiple recipients via HTTP, called the ID Connector Service.

  3. A process on the data source UCS server to monitor and configure the UCS@school ID Connector service, called the ID Connector HTTP API.

  4. Multiple recipients of the directory data relayed by the ID Connector Service. They run an HTTP-API service, that the ID Connector Service pushes updates to.

1.2. Admin prerequisites#

This administration chapter is useful when you need to administer an ID Connector setup, or you need to integrate ID Connector. To follow this text, you should be familiar with the following aspects of the UCS environment:

LDAP and LDAP listener#

LDAP is used because it is optimized for reading in a hierarchical structure. It shouldn’t be accessed directly, instead UDM should be used. OpenLDAP can have plugins, notifier being one of them that is heavily used in UCS. Upon changes in the LDAP directory, the notifier triggers listeners locally and on remote systems.

The listener service connects to all local or remote notifiers in the domain. The listener, when notified, calls listener modules, which are scripts (in shell and python)

You need to be able to:

  • understand the basic concepts of LDAP

See also

See LDAP directory service in UCS Manual [1].

Univention Directory Manager#

Univention Directory Manager (UDM) is used for handling user data (and other data) that is stored in the LDAP server, one of two core storage places (the other one is UCR). Examples for data are users, roles or machine info. UDM adds a layer of functionality and logic on top of LDAP, hence LDAP shouldn’t be used directly, but only through UDM.

You need to be able to:

  • understand the concept of UDM

  • know the basic structure of UDM objects and their attributes

  • add and manage extended attributes

See also

See Univention Directory Manager (UDM) in Univention Developer Reference [2].

Univention Configuration Registry#

The Univention Configuration Registry (UCR) stores configuration variables and settings to run the system, and creates and changes actual Linux configuration files as configured by these variables upon setting said variables.

You need to be able to:

  • understand basic UCR concepts

  • set and read UCR variables.

Univention App Center settings#

The Univention App Center is an ecosystem similar to the app stores known from mobile platforms like Apple or Google. It provides an infrastructure to build, deploy and run enterprise applications on Univention Corporate Server (UCS). The Univention App Center uses well-known technologies like Docker.

Within the app center, you can configure settings for the individual apps.

See also

UCS@school basics#

Schools have special requirements for managing what is going on inside them (teachers, students, staff, computer rooms, exams, etc.), and for managing the relation between multiple schools, their operator organizations (“Schulbetreiber”), and possibly ministerial departments above them.

There are several components used within UCS@school, Kelvin (see below) being one of them.

You need to be able to:

  • know about UCS@school objects

  • know the difference between UCS@school-objects and UDM objects

UCS@school Kelvin REST API#

The UCS@school Kelvin REST API (Kelvin) provides HTTP endpoints to create and manage individual UCS@school domain objects like school users, school classes and schools (OUs). It is written in FastAPI, hence in Python 3.

You need to be able to install and configure Kelvin.

See also

If you want to also develop for the ID Connector, please also see the next chapter Development.

1.3. Installation#

1.3.1. Sending system#

The app is available in the Univention App Center. You can install it with:

$ univention-app install ucsschool-id-connector

This runs the join script 50ucsschool-id-connector.inst, which creates:

  • the file /var/lib/univention-appcenter/apps/ucsschool-id-connector/conf/tokens.secret containing the key with which JWT tokens are signed.

  • the group ucsschool-id-connector-admins (with DN cn=ucsschool-id-connector-admins,cn=groups,$ldap_base) who’s members are allowed to access the ID Connector HTTP-API.

Use of both is explained later on in Authentication


You can check the existence of the group with:

$ udm groups/group list --filter cn=ucsschool-id-connector-admins


Join scripts are registered in LDAP and then executed on any UCS system either before/during/after the join process.

KB 13034 - A script shall be executed on each or a certain UCS systems before/during/after the join process

If the above didn’t get created, run:

$ univention-run-join-scripts --run-scripts --force 50ucsschool-id-connector.inst

This forces the (re-)running of the join script.

1.3.2. Receiving system#

In order for the ID Connector app to be able to create/modify/delete users on the target systems an HTTP-API is required on the target system. Currently only the Kelvin API is supported.


This only makes sense if the sender and target systems are in different domains, because in the same domain, users and groups already get synced using other UCS mechanisms.

Install the Kelvin API on each target system:

$ univention-app install ucsschool-kelvin-rest-api

To allow the ID Connector app on the sender system to access the Kelvin-API on the receiving system, it needs an authorized user account. By default, the Administrator account on the receiving system is the only authorized user. To add a dedicated Kelvin API user for the UCS@school ID Connector consult UCS@school Kelvin REST API documentation [4] on how to do that.

1.4. Configuration#

Now that everything is installed, let’s configure the setups. We configure the receiving system first, because we need auth credentials used on the receiving system later on the sending system.

1.4.1. Configure receiving system - HTTP-API (Kelvin)#

You need to install and configure the Kelvin API. This is documented in UCS@school Kelvin REST API documentation [4].

We assume that you have a current version of Kelvin installed after reading the documentation.


For the authorization of the UCS@school ID Connector at the target system it needs credentials with special privileges. Create a user with the name and password of your choice and add him to the group ucsschool-kelvin-rest-api-admins.

$ udm users/user create --position "cn=users,$(ucr get ldap/base)" \
  --set username=USERNAME-OF-YOUR-CHOICE --set lastname=Kelvin --set firstname=UCS \
  --set password="PASSWORD-OF-YOUR-CHOICE"

$ udm groups/group modify --dn "cn=ucsschool-kelvin-rest-api-admins,cn=groups,$(ucr get ldap/base)" \
  --append users="uid=USERNAME-OF-YOUR-CHOICE,cn=users,$(ucr get ldap/base)"

Note down the credentials, they are needed for the school authority configuration on the sending system further down.

WARNING: the password is now in the command history. You might want to delete this using e.g:

$ history -d -2

After installation and basic configuration you might want to configure mapped UDM properties.

Beyond the standard object properties in UCS@school you can define additional UDM properties that should be available in the Kelvin API on the target system.

For this you would define a configuration in /etc/ucsschool/kelvin/mapped_udm_properties.json, e.g.:

    "user": ["title", "phone", "e-mail"],
    "school": ["description"]

This would make the listed properties available for the user and school resources.

Kelvin needs to be restarted after changes to its configuration:

$ univention-app restart ucsschool-kelvin-rest-api


When configuring Kelvin in detail, remember that the password hashes for LDAP and Kerberos authentication are collectively transmitted in one JSON object to one target attribute. This means it’s all or nothing: all hashes are synced, even if empty. You can’t select individual hashes.


Please make sure that you configure all the mapped properties that the sending system sends, e.g. displayName. If the sender sends more than the receiver is configured to process, you will end up with unexpected errors, e.g. 404 in the log.

1.4.2. Configure sending system#

The school authorities configuration must be done through the ID Connector HTTP API. Do not edit configuration files directly.

UCS@school ID Connector HTTP API#

The HTTP-API of the ID Connector app offers three resources:

  • queues: monitoring of queues

  • school_authorities: configuration of school authorities

  • school_to_authority_mapping: configuration of which school we sync to which authority

You can discover the API interactively using one of two web interfaces. They can be visited with a browser at their respective URLs:

  • Swagger UI: https://FQDN/ucsschool-id-connector/api/v1/docs

  • ReDoc: https://FQDN/ucsschool-id-connector/api/v1/redoc

The Swagger UI page is especially helpful as it allows sending queries directly from the browser. The equivalent curl command lines are then displayed.

An OpenAPI v3 (formerly “Swagger”) schema can be downloaded from https://FQDN/ucsschool-id-connector/api/v1/openapi.json


Only members of the group ucsschool-id-connector-admins are allowed to access the HTTP-API.

The user Administrator is automatically added to this group for testing purposes. In production, only the regular admin user accounts should be used.

You can authorize yourself in e.g. the Swagger UI using the Authorize button.

To use the ID Connector HTTP API from a script, a JSON Web Token (JWT) must be retrieved from https://FQDN/ucsschool-id-connector/api/token. The token will be valid for a configurable amount of time (default 60 minutes), after which it must be renewed. To change the TTL of the token, open the corresponding app settings in the Univention App Center.

Example curl command to retrieve a token:

$ curl -i -k -X POST --data 'username=Administrator&password=s3cr3t' \

School authorities mapping#

We now need to configure two things:

  1. What school authorities do we send data to, and what data can they receive? This is described in this section.

  2. What actual schools are handled by which receiving system (school authority)? This is described in the following section: School to authority mapping.

We start with the first mapping, the one for school authorities.

In order to send user data to the target system, it must be decided which properties of which objects to send, and more important, which properties not to send.

E.g. there might be telephone numbers for students in the system on the sending side, but those should not be made available to the receiving school system. Instead of forbidding properties, we “map” properties on the sending side to properties on the receiving side.

Here is what the mapping related part of an example configuration looks like:

    "plugin_configs": {
        "kelvin": {
            "mapping": {
                "users": {
                    "ucsschoolRecordUID": "record_uid",
                    "ucsschoolSourceUID": "source_uid",
                    "roles": "roles"

This configures a mapping for the Kelvin plugin that sends the three defined properties to the receiving school:

  • The UDM ucsschoolRecordUID property should be synced to an UCS@school system as record_uid.

  • The UDM ucsschoolSourceUID property should be synced to an UCS@school system as source_uid.

  • The virtual roles property should be synced to an UCS@school system as roles


roles is virtual because there is special handling by the ID Connector app mapping ucsschoolRole to roles.


When creating users via Kelvin, some attributes are required and therefore have to be present within the mapping:

  "firstname": "firstname",
  "lastname": "lastname",
  "username": "name",
  "school": "school",
  "schools": "schools",
  "roles": "roles",
  "ucsschoolRecordUID": "record_uid",
  "ucsschoolSourceUID": "source_uid"

Here is a complete example that you can also find in the section School authority configuration.

  "name": "Traeger1",
  "url": "",
  "active": true,
  "plugins": [
  "plugin_configs": {
    "kelvin": {
      "username": "Administrator",
      "password": "univention",
      "mapping": {
        "users": {
          "firstname": "firstname",
          "lastname": "lastname",
          "username": "name",
          "disabled": "disabled",
          "mailPrimaryAddress": "email",
          "e-mail": "email",
          "birthday": "birthday",
          "school": "school",
          "schools": "schools",
          "school_classes": "school_classes",
          "title": "title",
          "displayName": "displayName",
          "userexpiry": "expiration_date",
          "phone": "phone",
          "roles": "roles",
          "ucsschoolRecordUID": "record_uid",
          "ucsschoolSourceUID": "source_uid"
        "school_classes": {
          "name": "name",
          "description": "description",
          "school": "school",
          "users": "users"
      "sync_password_hashes": true,
      "ssl_context": {
        "check_hostname": false

These are the keys in the configuration:

  • name identifies a specific receiving system. It is a free-form string. Adapt to your needs - and remember it, we need it in the next step.

  • username and password are the credentials that are needed on the receiving system. Use the credentials you created when configuring the receiving system.

  • The systems address is specified using url.

  • The users mapping inside plugin_configs[“kevlin”] is as described above, only a bit longer.

  • We also have a mapping for school_classes, which sets up the sync for those groups.

  • sync_password_hashes - if password hashed should be synced.

  • ssl_context - contains values that are passed to the ssl.SSLContext object which is used to communicate with the receiving system.

  • active - configures if this configuration for a an out queue for a school authority is active ( so you don’t have to delete it).

  • plugins - which plugins are going to be used for this school authority. Usually just “kelvin”.

Please adapt this to your needs, of course. The complete and adapted configuration needs to be posted to the school_authorities resource in the Swagger UI.

School to authority mapping#

This is the second of the two mappings we need.

While the above mapping defines which school authorities we have, we now need to map which school we sync to which authority - an authority could handle more than one school, so it’s an 1:n mapping.

The format is:

  "mapping": {

You can have one or more schools in the mapping.

So assuming you have a DEMOSCHOOL on your sending system, and you used the above configuration to define Traeger1 as a recipient system, you could do:

  "mapping": {
    "DEMOSCHOOL": "Traeger1"


Remember? Traeger refers to the receiving side of the sync process

You can also find this example in School to authority mapping example.

Please “PUT” this configuration JSON to the school_to_authority_mapping resource in the Swagger UI.

Role specific attribute mapping#


This is an advanced scenario. If you don’t need this, jump to the next section.

Back to our example about telephone numbers. Imagine that while telephone numbers should not be transferred for students, they are actually needed for teachers. This means, that we have a need to define per role which properties should be transferred.

With version 2.1.0 role specific attribute mapping was added to the default Kelvin plugin. This allows to define additional user mappings for each role (student, teacher, staff and school_admin) by adding a new mapping next to the users mapping suffixed by _$ROLE, e.g. users_student: {}.

If a user object is handled by the Kelvin plugin, the mapping is determined as follows:

  1. Determine the schools the current school authority is configured to handle.

  2. Determine all roles the user has in these schools.

  3. Order the roles by priority: school_admin being the highest, followed by staff, teacher and then student.

  4. Find a users_$ROLE mapping from the ones configured in the plugin settings, pick the one with the highest priority (from step 3).

  5. If none was found, fall back to the users mapping as the default.

An example for such a configuration can be found in Role specific Kelvin plugin mapping


The priority order for the roles was chosen in order of common specificity in UCS@school. A student only ever has the role student. But teachers, staff and school admins can have multiple roles.


The mappings for the different roles are not additive because that approach would complicate the option to remove mappings from a specific role. Therefore, only one mapping is chosen by the rules just described.


Users have the field school_classes, which describes which school classes they belong to. You might want to prevent certain user roles from being added or removed to school classes. Please be aware that leaving out the school_classes from the mapping is not sufficient to achieve this: changing the school classes of a user does not only result in a user change event but also a school class change event, which needs to be handled separately. You therefore need to use a derivative of the Kelvin plugin, which is described in the next section.

Partial group sync mapping#


This is an advanced scenario. If you don’t need this, jump to the next section.

Remember that in the last examples we had a property that we would send for some users, but not others, depending on their role? Turns out that we can have the same problem for groups.

Imagine that a school manages locally which teachers belong to which class. In the role specific mapping we would not sync the classes attribute school_classes, preventing overwriting the local managed settings (see above). This is not enough though: we would also need to make sure that we don’t sync the property users of groups which contains those teachers.

With version 2.1.0 a new derivative of the Kelvin plugin was added: kelvin-partial-group-sync. This plugin alters the handling of school class changes by allowing you to specify a list of roles that should be ignored when syncing groups. The following steps determine which members are sent to a school authority when a school class is added:

  1. Add all users that are members of the school class locally (Normal Kelvin plugin behavior).

  2. Remove all users that have a configured role to ignore in any school handled by the school authority configuration.

  3. Get all members of the school class on the target system that have one of the configured roles and add them.

  4. Get all members of the school class on the target system that are unknown to the ID Connector and add them.

This results in school classes having only members with roles not configured to ignore,

  • members with roles to ignore that were added on the target system,

  • any users added on the target system which are unknown to the ID Connector.


To achieve this behavior, several additional LDAP queries on the ID Connector and one additional request to the target system are necessary. This affects performance.

To activate this alternative behavior replace the kelvin plugin in a school authority configuration with kelvin-partial-group-sync. The configuration options are exactly the same as for the kelvin plugin, except for the addition of school_classes_ignore_roles, which holds the list of user roles to ignore for school class changes.

See Partial group sync for an example configuration.


Please be aware that this plugin can only alter the handling of dedicated school class change events. Due to the technical situation, changing the members of a school class often results in two events, a school class change and a user change. To actually prevent users of certain roles being added to school classes at all, it is necessary to leave out the mapping of the users school_class field in the configuration as well - see above.

1.5. Trying it out#

Time has come to try it out. What we want to do:

  1. Create a test user

  2. Import the test user on the sending side

  3. and watch the user being synced to the receiving side.

The slow way would be to create a user individually (and make sure to amend the required properties), or to use the UCS@school import. You can read all about importing users in UCS@school - Handbuch zur CLI-Import Schnittstelle [6] (German only).

We however do it the fast way, creating and importing the user in one step:

$ /usr/share/ucs-school-import/scripts/ucs-school-testuser-import \
  --students 1  --classes 1 DEMOSCHOOL

This will create a user within a class in the school DEMOSCHOOL.

Now watch the log file to see the sync action on the sender system:

$ tail -f /var/log/univention/ucsschool-id-connector/queues.log

In another terminal on the receiving system you can see the user being received by the Kelvin API:

$ tail -f /var/log/univention/ucsschool-kelvin-rest-api/http.log # kelvin log

You might need to wait a short moment before the queue picks up the new user. If everything went fine, you should see some messages in the kelvin log, and you can confirm that the user was created in either the Kelvin web interface at https://FQDN/ucsschool/kelvin/v1/docs or in the UMC.

These log files are also a good starting point for debugging in case something went wrong.


When debugging always make sure that the following is correct and matches:

  1. school authority configuration on the sender system (including auth credentials)

  2. school to authority mapping on the sender system

  3. mapped_udm_properties.json on the receiving system has all extra attributes that are defined in the school authority mapping.

Good luck! :-)

1.6. Starting / Stopping services#

Both services (ID Connector Service and ID Connector HTTP API) run in a Docker container. The container can be started/stopped by using the regular service facility of the host system:

$ univention-app start ucsschool-id-connector
$ univention-app status ucsschool-id-connector
$ univention-app stop ucsschool-id-connector
$ univention-app restart ucsschool-id-connector

To restart individual services, the init scripts inside the Docker container can be used. The univention-app program has a command that makes it easy to execute commands inside the Docker container:

# UCS@School ID Connector service
$ univention-app shell ucsschool-id-connector /etc/init.d/ucsschool-id-connector restart

# UCS@School ID Connector HTTP API
$ univention-app shell ucsschool-id-connector /etc/init.d/ucsschool-id-connector-rest-api start

1.7. Updates#

Updates are installed in one of the two usual UCS ways. Either via UMC or on the command line:

$ univention-upgrade

# or just:

$ univention-app upgrade ucsschool-id-connector

1.8. Extra: setting up a second school authority#

If we already have a school authority set up and want to set up a second one (by copying its configuration) we can do the following:

  1. Make sure the new school authority server has the Kelvin app installed and running.

  2. Retrieve the configuration for our old school authority.

    For this we open the HTTP-API Swagger UI ( https://FQDN/ucsschool-id-connector/api/v1/docs) and authenticate ourselves. The button can be found in the top right corner of the page.

    Then we retrieve a list of the available school authorities by using the GET /ucsschool-id-connector/api/v1/school_authorities tab, by clicking on Try it out and Execute.

    In the response body, we get a JSON list of the school authorities that are currently configured. We need to copy the one we want to replicate and save it for later.

  3. Under POST /ucsschool-id-connector/api/v1/school_authorities we can create the new school authority.

    Click try it out and insert the copied JSON object from before into the request body.

    Now we just have to alter the name, URL, and login credentials before executing the request.

    • The URL has to point to the new school authorities HTTP-API.

    • The name can be chosen at your leisure

    • The password is the authentication token of the school authorities HTTP-API (retrieved earlier).

The tab PATCH /ucsschool-id-connector/api/v1/school_authorities/{name} can be used to change an already existing configuration.

To retrieve a list of the extended attributes on the old school authority server, one can use:

$ udm settings/extended_attribute list