Github user ifilonenko commented on a diff in the pull request:
https://github.com/apache/spark/pull/21669#discussion_r215470727
--- Diff: docs/security.md ---
@@ -722,6 +722,62 @@ with encryption, at least.
The Kerberos login will be periodically renewed using the provided
credentials, and new delegation
tokens for supported will be created.
+## Secure Interaction with Kubernetes
+
+When talking to Hadoop-based services behind Kerberos, it was noted that
Spark needs to obtain delegation tokens
+so that non-local processes can authenticate. These delegation tokens in
Kubernetes are stored in Secrets that are
+shared by the Driver and its Executors. As such, there are three ways of
submitting a kerberos job:
+
+1. Submitting with a $kinit that stores a TGT in the Local Ticket Cache:
+```bash
+/usr/bin/kinit -kt <keytab_file> <username>/<krb5 realm>
+/opt/spark/bin/spark-submit \
+ --deploy-mode cluster \
+ --class org.apache.spark.examples.HdfsTest \
+ --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
+ --conf spark.executor.instances=1 \
+ --conf spark.app.name=spark-hdfs \
+ --conf spark.kubernetes.container.image=spark:latest \
+ --conf spark.kubernetes.kerberos.krb5location=/etc/krb5.conf \
+
local:///opt/spark/examples/jars/spark-examples_2.11-2.4.0-SNAPSHOT.jar \
+ <HDFS_FILE_LOCATION>
+```
+3. Submitting with a local keytab and principle
+```bash
+/opt/spark/bin/spark-submit \
+ --deploy-mode cluster \
+ --class org.apache.spark.examples.HdfsTest \
+ --master k8s://<KUBERNETES_MASTER_ENDPOINT> \
+ --conf spark.executor.instances=1 \
+ --conf spark.app.name=spark-hdfs \
+ --conf spark.kubernetes.container.image=spark:latest \
+ --conf spark.kubernetes.kerberos.keytab=<KEYTAB_FILE> \
+ --conf spark.kubernetes.kerberos.principal=<PRINCIPLE> \
+ --conf spark.kubernetes.kerberos.krb5location=/etc/krb5.conf \
+
local:///opt/spark/examples/jars/spark-examples_2.11-2.4.0-SNAPSHOT.jar \
+ <HDFS_FILE_LOCATION>
+```
+
+3. Submitting with pre-populated secrets already existing within the
namespace
--- End diff --
Agreed, I should be more clear. This is a secret containing the Delegation
Token that will be used to mount onto the driver and executors, pointed to via
the ENV: `HADOOP_TOKEN_FILE_LOCATION`
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