Taking a mandatory snapshot of HDP tables

Taking a snapshot of Hive tables is mandatory before upgrading or migrating. You also need to keep track of how many tables you have before and after for comparison.

In Ambari, go to Services/Hive/Configs, and check the value of hive.metastore.warehouse.dir to determine the location of the Hive warehouse, /apps/hive/warehouse by default.

On any node in the cluster, as the HDFS superuser, enable snapshots.

$ sudo su - hdfs
$ hdfs dfsadmin -allowSnapshot /apps/hive/warehouse

Allowing snapshot on /apps/hive/warehouse succeeded

Create a snapshot of the Hive warehouse.

$ hdfs dfs -createSnapshot /apps/hive/warehouse

Output includes the name and location of the snapshot.

Created snapshot /apps/hive/warehouse/.snapshot/s20181204-164645.898

Start Hive as a user who has SELECT privileges on the tables.

$ beeline 
beeline> !connect jdbc:hive2:// 
Enter username for jdbc:hive2://: hive
Enter password for jdbc:hive2://: *********

Connected to: Apache Hive (version 1.2.1000.2.6.5.0-292)
Driver: Hive JDBC (version 1.2.1000.2.6.5.0-292)

Identify all tables outside /apps/hive/warehouse/.
```
hive> USE my_database;
hive> SHOW TABLES;
```
Determine the location of each table using the DESCRIBE command. For example:
```
hive> DESCRIBE FORMATTED my_table partition (dt='20181130');
```
Create a snapshot of the directory shown in the location section of the output.
Repeat steps 5-7 for each database and its tables outside /apps/hive/warehouse/.