Domain-specific configuration

Domain-specific configuration

The Identity service supports domain-specific Identity drivers. The drivers allow a domain to have its own LDAP or SQL back end. By default, domain-specific drivers are disabled.

Domain-specific Identity configuration options can be stored in domain-specific configuration files, or in the Identity SQL database using API REST calls.


Storing and managing configuration options in an SQL database is experimental in Kilo, and added to the Identity service in the Liberty release.

Enable drivers for domain-specific configuration files

To enable domain-specific drivers, set these options in the /etc/keystone/keystone.conf file:

domain_specific_drivers_enabled = True
domain_config_dir = /etc/keystone/domains

When you enable domain-specific drivers, Identity looks in the domain_config_dir directory for configuration files that are named as keystone.DOMAIN_NAME.conf. A domain without a domain-specific configuration file uses options in the primary configuration file.

Enable drivers for storing configuration options in SQL database

To enable domain-specific drivers, set these options in the /etc/keystone/keystone.conf file:

domain_specific_drivers_enabled = True
domain_configurations_from_database = True

Any domain-specific configuration options specified through the Identity v3 API will override domain-specific configuration files in the /etc/keystone/domains directory.

Unlike the file-based method of specifying domain-specific configurations, options specified via the Identity API will become active without needing to restart the keystone server. For performance reasons, the current state of configuration options for a domain are cached in the keystone server, and in multi-process and multi-threaded keystone configurations, the new configuration options may not become active until the cache has timed out. The cache settings for domain config options can be adjusted in the general keystone configuration file (option cache_time in the domain_config group).


It is important to notice that when using either of these methods of specifying domain-specific configuration options, the main keystone configuration file is still maintained. Only those options that relate to the Identity driver for users and groups (i.e. specifying whether the driver for this domain is SQL or LDAP, and, if LDAP, the options that define that connection) are supported in a domain-specific manner. Further, when using the configuration options via the Identity API, the driver option must be set to an LDAP driver (attempting to set it to an SQL driver will generate an error when it is subsequently used).

For existing installations that already use file-based domain-specific configurations who wish to migrate to the SQL-based approach, the keystone-manage command can be used to upload all configuration files to the SQL database:

$ keystone-manage domain_config_upload --all

Once uploaded, these domain-configuration options will be visible via the Identity API as well as applied to the domain-specific drivers. It is also possible to upload individual domain-specific configuration files by specifying the domain name:

$ keystone-manage domain_config_upload --domain-name DOMAINA


It is important to notice that by enabling either of the domain-specific configuration methods, the operations of listing all users and listing all groups are not supported, those calls will need either a domain filter to be specified or usage of a domain scoped token.


Keystone does not support moving the contents of a domain (i.e. “its” users and groups) from one backend to another, nor group membership across backend boundaries.


When using the file-based domain-specific configuration method, to delete a domain that uses a domain specific backend, it’s necessary to first disable it, remove its specific configuration file (i.e. its corresponding keystone.<domain_name>.conf) and then restart the Identity server. When managing configuration options via the Identity API, the domain can simply be disabled and deleted via the Identity API; since any domain-specific configuration options will automatically be removed.


Although keystone supports multiple LDAP backends via the above domain-specific configuration methods, it currently only supports one SQL backend. This could be either the default driver or a single domain-specific backend, perhaps for storing service users in a predominantly LDAP installation.


Keystone has deprecated the keystone-manage domain_config_upload option. The keystone team recommends setting domain config options via the API instead.

Due to the need for user and group IDs to be unique across an OpenStack installation and for keystone to be able to deduce which domain and backend to use from just a user or group ID, it dynamically builds a persistent identity mapping table from a public ID to the actual domain, local ID (within that backend) and entity type. The public ID is automatically generated by keystone when it first encounters the entity. If the local ID of the entity is from a backend that does not guarantee to generate UUIDs, a hash algorithm will generate a public ID for that entity, which is what will be exposed by keystone.

The use of a hash will ensure that if the public ID needs to be regenerated then the same public ID will be created. This is useful if you are running multiple keystones and want to ensure the same ID would be generated whichever server you hit.

While keystone will dynamically maintain the identity mapping, including removing entries when entities are deleted via the keystone, for those entities in backends that are managed outside of keystone (e.g. a read-only LDAP), keystone will not know if entities have been deleted and hence will continue to carry stale identity mappings in its table. While benign, keystone provides an ability for operators to purge the mapping table of such stale entries using the keystone-manage command, for example:

$ keystone-manage mapping_purge --domain-name DOMAINA --local-id

A typical usage would be for an operator to obtain a list of those entries in an external backend that had been deleted out-of-band to keystone, and then call keystone-manage to purge those entries by specifying the domain and local-id. The type of the entity (i.e. user or group) may also be specified if this is needed to uniquely identify the mapping.

Since public IDs can be regenerated with the correct generator implementation, if the details of those entries that have been deleted are not available, then it is safe to simply bulk purge identity mappings periodically, for example:

$ keystone-manage mapping_purge --domain-name DOMAINA

will purge all the mappings for DOMAINA. The entire mapping table can be purged with the following command:

$ keystone-manage mapping_purge --all

Generating public IDs in the first run may take a while, and most probably first API requests to fetch user list will fail by timeout. To prevent this, mapping_populate command should be executed. It should be executed right after LDAP has been configured or after mapping_purge.

$ keystone-manage mapping_populate --domain DOMAINA

Public ID Generators

Keystone supports a customizable public ID generator and it is specified in the [identity_mapping] section of the configuration file. Keystone provides a sha256 generator as default, which produces regenerable public IDs. The generator algorithm for public IDs is a balance between key size (i.e. the length of the public ID), the probability of collision and, in some circumstances, the security of the public ID. The maximum length of public ID supported by keystone is 64 characters, and the default generator (sha256) uses this full capability. Since the public ID is what is exposed externally by keystone and potentially stored in external systems, some installations may wish to make use of other generator algorithms that have a different trade-off of attributes. A different generator can be installed by configuring the following property:


Changing the generator may cause all existing public IDs to be become invalid, so typically the generator selection should be considered immutable for a given installation.

Migrate domain-specific configuration files to the SQL database

You can use the keystone-manage command to migrate configuration options in domain-specific configuration files to the SQL database:

# keystone-manage domain_config_upload --all

To upload options from a specific domain-configuration file, specify the domain name:

# keystone-manage domain_config_upload --domain-name DOMAIN_NAME
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