Each host that comprises a node in a Cloudera cluster runs an operating system, such as CentOS or Oracle Linux. At the OS-level, there are user:group accounts created during installation that map to the services running on that specific node of the cluster. The default shell-based group mapping provider, org.apache.hadoop.security.ShellBasedUnixGroupsMapping, handles the mapping from the local host system (the OS) to the specific cluster service, such as HDFS. The hosts authenticate using these local OS accounts before processes are allowed to run on the node.

For clusters integrated with Kerberos for authentication, the hosts must also provide Kerberos tickets before processes can run on the node. The cluster can use the organization's LDAP directory service to provide the login credentials, including Kerberos tickets, to authenticate transparently while the system runs. That means that the local user:group accounts on each host must be mapped to LDAP accounts. To map local user:group accounts to an LDAP service:

• Use tools such as SSSD (Systems Security Services Daemon) or Centrify Server Suite (see Identity and Access management for Cloudera).
• The Hadoop LdapGroupsMapping group mapping mechanism. The LdapGroupsMapping library may not be as robust a solution needed for large organizations in terms of scalability and manageability, especially for organizations managing identity across multiple systems and not exclusively for Hadoop clusters. Support for the LdapGroupsMapping library is not consistent across all operating systems.
• Do not use Winbind to map Linux user:group accounts to Active Directory. It cannot scale, impedes cluster performance, and is not supported.
• Use the same user:group mappings across all cluster nodes, for ease of management.
• Use either Cloudera Manager or the command-line process detailed below.

The local user:group accounts must be mapped to LDAP for group mappings in Hadoop. You must create the users and groups for your Hadoop services in LDAP.

To integrate the cluster with an LDAP service, the user:group relationships must be contained in the LDAP directory. The admin must create the user accounts and define groups for user:group relationships on each host.

The user and group names listed in the table are the default user:group values for CDH services.

  Note: If the defaults have been changed for any service, use the custom values to create the users and configure the group for that service in the LDAP server, rather than the defaults listed in the table below. For example, you changed the defaults in the Cloudera Manager Admin Console to customize the System User or System Group setting for the service.

  Note: Cloudera Manager 5.3 (and later releases) can be deployed in single user mode. In single user mode, Hadoop users and groups are subsumed by cloudera-scm:cloudera-scm. Cloudera Manager starts all Cloudera Manager Agent processes and services running on the nodes in the cluster as a unit owned by this cloudera-scm:cloudera-scm. Single user mode is not recommended for production clusters.