Each service in HDP must have its own principal. As services do not login with a password to acquire their tickets, their principal's authentication credentials are stored in a keytab file, which is extracted from the Kerberos database and stored locally with the service principal. First you must create the principal, using mandatory naming conventions. Then you must create the keytab file with that principal's information and copy the file to the keytab directory on the appropriate service host.
Step 1: Create a service principal using the
kadmin
utility:
kadmin: addprinc -randkey $<principal_name>/<fully.qualified.domain.name>@YOUR-REALM.COM
You must have a principal with administrative permissions to use this command. The randkey is used to generate the password.
Note that in the example each service principal's name has appended to it the fully qualified domain name of the host on which it is running. This is to provide a unique principal name for services that run on multiple hosts, like DataNodes and TaskTrackers. The addition of the hostname serves to distinguish, for example, a request from DataNode A from a request from DataNode B. This is important for two reasons:
If the Kerberos credentials for one DataNode are compromised, it does not automatically lead to all DataNodes being compromised
If multiple DataNodes have exactly the same principal and are simultaneously connecting to the NameNode, and if the Kerberos authenticator being sent happens to have same timestamp, then the authentication would be rejected as a replay request.
The <principal name> part of the name must match the values in the table below. Note that the NameNode, Secondary NameNode, and Oozie require two principals each:
Table 13.1. Service Principal Names
| Service Name | Mandatory Principal Name |
|---|---|
|
NameNode |
|
|
Secondary NameNode |
|
|
JobTracker |
|
|
TaskTracker |
|
|
DataNode |
|
|
HBase Master |
|
|
HBase RegionServer |
|
|
HCatalog Server |
|
|
Oozie |
|
|
WebHCat (Templeton) |
|
For example: To create the principal for a DataNode service, issue this command:
kadmin: addprinc -randkey dn/<datanode-host>@EXAMPLE.COM
Step 2: Extract the related keytab file and place
it in the keytab directory (by default /etc/krb5.keytab) of the
appropriate respective
components:
kadmin: xst -norandkey -k $<keytab_file_name> $<principal_name>/fully.qualified.domain.name
You must use the mandatory names for the $<keytab_file_name> variable shown in this table.
Table 13.2. Service Keytab File Names
| Service Name | Mandatory Keytab File Name |
|---|---|
|
NameNode |
AND
|
|
Secondary NameNode |
AND
|
|
JobTracker |
|
|
TaskTracker |
|
|
DataNode |
|
|
HBase Master |
|
|
HBase RegionServer |
|
|
HCatalog Server |
|
|
Oozie |
AND
|
|
Templeton |
|
For example: To create the keytab files for the NameNode, issue these commands:
kadmin: xst -k nn.service.keytab nn/<namenode-host> kadmin: xst -k spnego.service.keytab HTTP/<namenode-host>
When
you have created the keytab files, copy them to the keytab
directory of the respective service hosts.
Step 3: Verify that the correct keytab files and
principals are associated with the correct service using the
klist command. For example, on the
NameNode:
klist –k -t /etc/security/nn.service.keytab
Do this on each respective service in your cluster.
