Step 2: Migrate Databases from the Embedded Database Server to the External PostgreSQL Database Server

After you identify the roles that use the embedded database server, you can migrate from the Cloudera Manager embedded database server to the external PostgreSQL database server. When you migrate, you export the PostgreSQL user roles from the embedded database, import the PostgreSQL user roles into the external database, import the Cloudera Manager database on the external database server, and perform other tasks.

Minimum Required Role: Operator (also provided by Configurator, Cluster Administrator, Limited Cluster Administrator , and Full Administrator)

While performing this procedure, ensure that the Cloudera Manager Agents remain running on all hosts. Unless otherwise specified, when prompted for a password use the cloudera-scm password.

In Cloudera Manager, stop the cluster services identified in the previous step as using the embedded database server. Be sure to stop the Cloudera Management Service as well. Also be sure to stop any services with dependencies on these services. The remaining CDH services will continue to run without downtime.

note
If you do not stop the services from within Cloudera Manager before stopping Cloudera Manager Server from the command line, they will continue to run and maintain a network connection to the embedded database server. If this occurs, then the embedded database server will ignore any command line stop commands (Step 2) and require that you manually stop the process, which in turn causes the services to crash instead of stopping cleanly.
Navigate to Hosts > All Hosts, and make note of the number of roles assigned to hosts. Also take note whether or not they are in a commissioned state. You will need this information later to validate that your scm database was migrated correctly.
Stop the Cloudera Manager Server. To stop the server:
```
sudo service cloudera-scm-server stop
```
Obtain and save the embedded database superuser password (you will need this password in subsequent steps) from the generated_password.txt file:
```
head -1  /var/lib/cloudera-scm-server-db/data/generated_password.txt
```
Export the PostgreSQL user roles from the embedded database server to ensure the correct users, permissions, and passwords are preserved for database access. Passwords are exported as an md5sum and are not visible in plain text. To export the database user roles (you will need the cloudera-scm user password):
```
pg_dumpall -h localhost -p 7432 -U cloudera-scm -v --roles-only -f "/var/tmp/cloudera_user_roles.sql"
```
important
If you see the version mismatch between the existing PostgreSQL Database server and the utilities of the new external PostgreSQL Database server, then Cloudera recommends creating a symlink with the related PostgreSQL utilities such as pg_dumpall, pg_dump, and pg_restore to ensure the pg utility commands work successfully.
Run the following command to create a symlink with the pg_dumpall utility:
sudo ln -sf /usr/pgsql-<existing PostgreSQL Database server version>/bin/pg_dumpall /usr/bin/pg_dumpall
Edit /var/tmp/cloudera_user_roles.sql to remove any CREATE ROLE and ALTER ROLE commands for databases not in your list. Leave the entries for cloudera-scm untouched, because this user role is used during the database import.
Export the data from each of the databases on your list you created when you identified roles that use the embedded database server:
```
pg_dump -F c -h localhost -p 7432 -U cloudera-scm [database_name]  > /var/tmp/[database_name]_db_backup-$(date +”%m-%d-%Y”).dump
```
The following is a sample data export command for the scm database:
```
pg_dump -F c -h localhost -p 7432 -U cloudera-scm scm > /var/tmp/scm_db_backup-$(date +%m-%d-%Y).dump
```
```
Password:
```
important
If you see the version mismatch between the existing PostgreSQL Database server and the utilities of the new external PostgreSQL Database server, then Cloudera recommends creating a symlink with the related PostgreSQL utilities such as pg_dumpall, pg_dump, and pg_restore to ensure the pg utility commands work successfully.
Run the following command to create a symlink with the pg_dump utility:
sudo ln -sf /usr/pgsql-<existing PostgreSQL Database server version>/bin/pg_dump /usr/bin/pg_dump
Stop and disable the embedded database server:
```
service cloudera-scm-server-db stop
chkconfig cloudera-scm-server-db off
```
Confirm that the embedded database server is stopped:
```
netstat -at | grep 7432
```

Back up the Cloudera Manager Server database configuration file:

cp /etc/cloudera-scm-server/db.properties /etc/cloudera-scm-server/db.properties.embedded

Copy the file /var/tmp/cloudera_user_roles.sql and the database dump files from the embedded database server host to /var/tmp on the external database server host:
```
cd /var/tmp
scp cloudera_user_roles.sql *.dump <user>@<postgres-server>:/var/tmp
```
Import the PostgreSQL user roles into the external database server.
The external PostgreSQL database server superuser password is required to import the user roles. If the superuser role has been changed, you will be prompted for the username and password.
note
Only run the command that applies to your context; do not execute both commands.
- To import users when using the default PostgreSQL superuser role:
```
sudo -u postgres psql -f /var/tmp/cloudera_user_roles.sql
```
- To import users when the superuser role has been changed:
```
psql -h <database-hostname> -p <database-port> -U <superuser> -f /var/tmp/cloudera_user_roles.sql
```
  For example:
```
psql -h pg-server.example.com -p 5432 -U postgres -f /var/tmp/cloudera_user_roles.sql
```
```
Password for user postgres
```
Import the Cloudera Manager database on the external server. First copy the database dump files from the Cloudera Manager Server host to your external PostgreSQL database server, and then import the database data:

note
To successfully run the pg_restore command, there must be an existing database on the database server to complete the connection; the existing database will not be modified. If the -d <existing-database> option is not included, then the pg_restore command will fail.
```
pg_restore -C -h <database-hostname> -p <database-port> -d <existing-database> -U cloudera-scm -v <data-file>
```
Repeat this import for each database.
The following example is for the scm database:
```
pg_restore -C -h pg-server.example.com -p 5432 -d postgres -U cloudera-scm -v /var/tmp/scm_server_db_backup-20180312.dump
```
```
pg_restore: connecting to database for restore
Password:
```
important
If you see the version mismatch between the existing PostgreSQL Database server and the utilities of the new external PostgreSQL Database server, then Cloudera recommends creating a symlink with the related PostgreSQL utilities such as pg_dumpall, pg_dump, and pg_restore to ensure the pg utility commands work successfully.
Run the following command to create a symlink with the pg_restore utility:
sudo ln -sf /usr/pgsql-<existing PostgreSQL Database server version>/bin/pg_restore /usr/bin/pg_restore
Update the Cloudera Manager Server database configuration file to use the external database server. Edit the /etc/cloudera-scm-server/db.properties file as follows:
1. Update the com.cloudera.cmf.db.host value with the hostname and port number of the external database server.
2. Change the com.cloudera.cmf.db.setupType value from "EMBEDDED" to "EXTERNAL".
Start the Cloudera Manager Server and confirm it is working:
```
service cloudera-scm-server start
```
Note that if you start the Cloudera Manager GUI at this point, it may take up to five minutes after executing the start command before it becomes available.
In Cloudera Manager Server, navigate to Hosts > All Hosts and confirm the number of roles assigned to hosts (this number should match what you found in Step 2); also confirm that they are in a commissioned state that matches what you observed in Step 2.
Update the role configurations to use the external database hostname and port number. Only perform this task for services where the database has been migrated.
- For Cloudera Management Services:
  1. Select Cloudera Management Service > Configuration, and type "7432" in the Search field.
  2. Change any database hostname properties from the embedded database to the external database hostname and port number.
  3. Click Save Changes.
- For the Oozie Service:
  1. Select Oozie service > Configuration, and type "7432" in the Search field.
  2. Change any database hostname properties from the embedded database to the external database hostname and port number.
  3. Click Save Changes.
- For Hive, Hue, and Sentry Services:
  1. Select the specific service > Configuration, and type "database host" in the Search field.
  2. Change the hostname from the embedded database name to the external database hostname.
  3. Click Save Changes.
Start the Cloudera Management Service and confirm that all management services are up and no health tests are failing.
Start all Services via the Cloudera Manager web UI. This should start all services that were stopped for the database migration. Confirm that all services are up and no health tests are failing.
On the embedded database server host, remove the embedded PostgreSQL database server:
1. Make a backup of the /var/lib/cloudera-scm-server-db/data directory:
```
tar czvf /var/tmp/embedded_db_data_backup-$(date +”%m-%d-%Y”).tgz /var/lib/cloudera-scm-server-db/data
```
2. Remove the embedded database package:
  For RHEL/SLES:
```
rpm --erase cloudera-manager-server-db-2
```
  For Debian/Ubuntu:
```
apt-get remove cloudera-manager-server-db-2
```
3. Delete the /var/lib/cloudera-scm-server-db/data directory.