OSS-HDFS supports RootPolicy. You can use RootPolicy to configure a custom prefix for OSS-HDFS. This way, jobs can run on OSS-HDFS without modifying the original access prefix hdfs://.

Prerequisites

JindoSDK 4.6.0 or later is used. To download the package, visit GitHub.

Procedure

Configure RootPolicy.
Run the following SetRootPolicy command to specify an address that contains a custom prefix for a bucket:
```
jindo admin -setRootPolicy oss://<bucket_name>.<dls_endpoint>/ hdfs://<your_ns_name>/
```
The following items describe the parameters of the SetRootPolicy command:
- <bucket_name>: Specify the name of the bucket for which OSS-HDFS is enabled.
- <dls_endpoint>: Specify the endpoint of the region in which OSS-HDFS is enabled. Example: cn-hangzhou.oss-dls.aliyuncs.com.
  If you do not want to repeatedly add the <dls_endpoint> parameter to the SetRootPolicy command each time you run a RootPolicy command, you can use one of the following methods to add configuration items to the core-site.xml file of Hadoop:
  - Method 1:
```
<configuration>
    <property>
        <name>fs.oss.endpoint</name>
        <value><dls_endpoint></value>
    </property>
</configuration>
```
  - Method 2:
```
<configuration> 
 <property>
        <name>fs.oss.bucket.<bucket_name>.endpoint</name>
        <value><dls_endpoint></value>
    </property>
</configuration>
```
    After the preceding configuration is complete, the preceding command can be simplified into the following format:
```
jindo admin -setRootPolicy oss://<bucket_name>/ hdfs://<your_ns_name>/
```
- <your_ns_name>: Specify the custom nsname that is used to access OSS-HDFS. A non-empty string is supported, such as test. The current version supports only the root directory.
Configure Access Policy discovery address and Scheme implementation class.

You must configure the following parameters in the core-site.xml file of Hadoop:

<configuration>
    <property>
        <name>fs.accessPolicies.discovery</name>
        <value>oss://<bucket_name>.<dls_endpoint>/</value>
    </property>
    <property>
        <name>fs.AbstractFileSystem.hdfs.impl</name>
        <value>com.aliyun.jindodata.hdfs.HDFS</value>
    </property>
    <property>
        <name>fs.hdfs.impl</name>
        <value>com.aliyun.jindodata.hdfs.JindoHdfsFileSystem</value>
    </property>
</configuration>

If you want to configure Access Policy discovery addresses and Scheme implementation classes for multiple buckets, separate the buckets with commas (,).

Run the following command to check whether RootPolicy is successfully configured:

hadoop fs -ls hdfs://<your_ns_name>/

If the following results are returned, RootPolicy is successfully configured:

drwxr-x--x   - hdfs  hadoop          0 2023-01-05 12:27 hdfs://<your_ns_name>/apps
drwxrwxrwx   - spark hadoop          0 2023-01-05 12:27 hdfs://<your_ns_name>/spark-history
drwxrwxrwx   - hdfs  hadoop          0 2023-01-05 12:27 hdfs://<your_ns_name>/tmp
drwxrwxrwx   - hdfs  hadoop          0 2023-01-05 12:27 hdfs://<your_ns_name>/user

Use a custom prefix to access OSS-HDFS.
After you restart services such as Hive and Spark, you can access OSS-HDFS by using a custom prefix.
(Optional) Use RootPolicy for other purposes.
- List all addresses that contain a custom prefix specified for a bucket
  Run the following listAccessPolicies command to list all registered prefix addresses of a specific bucket:
```
jindo admin -listAccessPolicies oss://<bucket_name>.<dls_endpoint>/
```
- Delete all registered prefix addresses of a specific bucket
  Run the following unsetRootPolicy command to delete all registered prefix addresses of a specified bucket:
```
jindo admin -unsetRootPolicy oss://<bucket_name>.<dls_endpoint>/ hdfs://<your_ns_name>/
```