Rolling Back a Cloudera Private Cloud Base Upgrade from version 7.1.8 to CDH 6

Review Limitations

The rollback procedure has the following limitations:

HDFS – If you have finalized the HDFS upgrade, you cannot roll back your cluster.
Compute clusters – Rollback for Compute clusters is not supported. You must remove any compute clusters before rolling back.
Configuration changes, including the addition of new services or roles after the upgrade, are not retained after rolling back Cloudera Manager.
Cloudera recommends that you not make configuration changes or add new services and roles until you have finalized the HDFS upgrade and no longer require the option to roll back your upgrade.
HBase – If your cluster is configured to use HBase replication, data written to HBase after the upgrade might not be replicated to peers when you start your rollback. This topic does not describe how to determine which, if any, peers have the replicated data and how to roll back that data. For more information about HBase replication, see HBase Replication.
Sqoop 2 – As described in the upgrade process, Sqoop2 had to be stopped and deleted before the upgrade process and therefore will not be available after the rollback.
Kafka – Once the Kafka log format and protocol version configurations (the inter.broker.protocol.version and log.message.format.version properties) are set to the new version (or left blank, which means to use the latest version), Kafka rollback is not possible.

Stop the Cluster

If HBase is deployed in the cluster do the following before stopping the cluster:
The HBase Master procedures changed between the two versions, so if a procedure was started by HBase 2.2 (CDP 7.x) then the older HBase 2.1 won't be able to continue the procedure after the rollback. For this reason the Procedure Store in HBase Master must be cleaned before the rollback. If CDP 7.x HBase Master was never started, then the rollback should be fine. But if HBase Master was running with the new version and there is any ongoing (or stuck) HBase Master Procedure present in the CDP 7 HBase Master, then the older CDH 6 HBase Master will fail to start after the rollback. If this happens, HBase will need manual fix after the rollback (e.g. the sidelining of the HBase Master Procedure WAL files and the potential fixing of inconsistencies in HBase).
To avoid this problem, you should try to verify that no unfinished procedure is present before stopping HBase Master on the CDP 7.x Cluster. Please follow these steps:
1. Make sure there was no traffic running against the HBase Cluster recently (in the last 10 minutes) that can trigger e.g. table creation or deletion, region assignment or split or merge, etc.
2. Disable automatic Balancer and Normalizer in HBase. Also disable Split and Merge procedures, before stopping the CDP 7 Cluster. All these tools in HBase can cause the starting of new HBase Master Procedures, which we want to avoid now. Issue the following commands in HBase Shell:
```
balance_switch false
normalizer_switch false
splitormerge_switch 'SPLIT', false
splitormerge_switch 'MERGE', false
```
3. Check the list of procedures on the HBase Master Web UI (In Cloudera Manager, go to the HBase service and open the HBase Web UI > Procedures & Locks tab). Wait until you see procedures only with final states like 'SUCCESS', 'FAILED' or 'ROLLEDBACK'.
4. Get the list of procedures from HBase shell using the 'list_procedures' command. Wait until you see procedures only with final states like 'SUCCESS', 'FAILED' or 'ROLLEDBACK'. The State appears in the third column of the table returned by the 'list_procedures' command.
If the HBase Master doesn't start after the rollback and some procedure-related exceptions are found in the role logs (like "BadProcedureException" or decode errors in the "ProcedureWALFormatReader" class, or "ClassNotFoundException" for procedure classes), then this is most likely caused by CDP 7 procedures that still remain in the procedure WAL files. In this case, please open a ticket for Cloudera customer support, who will help you to sideline the procedure WAL files and fix any potential inconsistencies in HBase.
On the Home > Status tab, click the Actions menu and select Stop.
Click Stop in the confirmation screen. The Command Details window shows the progress of stopping services.
When All services successfully stopped appears, the task is complete and you can close the Command Details window.
Go to the YARN service and click Actions > Clean NodeManager Recovery Directory. The CDH 6 NodeManager will not start up after the downgrade if it finds CDP 7.x data in the recovery directory. The format and content of the NodeManager's recovery state store was changed between CDH 6.x and CDP 7.x. The recovery directory used by CDP 7.x must be cleaned up as part of the downgrade to CDH 6.

(Parcels) Downgrade the Software

Follow these steps only if your cluster was upgraded using Cloudera parcels.

Log in to the Cloudera Manager Admin Console.
Select Hosts > Parcels.
A list of parcels displays.
Locate the CDH 6 parcel and click Activate. (This automatically deactivates the Cloudera Private Cloud Base 7 parcel.) See Activating a Parcel for more information. If the parcel is not available, use the Download button to download the parcel.
important
If you added new services that are not part of CDH 6 during the upgrade, a list of services that need to be deleted displays. You must delete these services before activating the CDH 6 parcel.
If you include any additional components in your cluster, such as Search or Impala, click Activate for those parcels.
If the Ranger service is deployed in the cluster, disable the Ranger plugin from the services below, if they are deployed in the cluster:
- HDFS: Go to the HDFS service > Configurations and disable the Enable Ranger Authorization configuration property.
- Hive: Go to the Hive service > Configurations and delete the Ranger Service configuration property.
- Kafka: Go to the Kafka service > Configurations and delete the Ranger Service configuration property.
- Impala Go to the Impala service > Configurations > delete the Ranger Service configuration property.
After performing the above steps to disable the plugin, Stop the Ranger service and delete it.
The Sentry service will be added when you perform the Restore Cloudera Manager Databases steps, later in this rollback procedure. The Sentry service will be added in Cloudera Manager and will continue to use the database configuration saved in Cloudera Manager.

Stop Cloudera Manager

Stop the Cloudera Management Service.
1. Log in to the Cloudera Manager Admin Console.
2. Select Clusters > Cloudera Management Service.
3. Select Actions > Stop.
Stop the Cloudera Manager Server.
```
sudo systemctl stop cloudera-scm-server
```
Hard stop the Cloudera Manager agents. Run the following command on all hosts:
```
sudo systemctl stop cloudera-scm-supervisord.service
```

Restore Cloudera Manager Databases

Restore the Cloudera Manager databases from the backup of Cloudera Manager that was taken before upgrading the cluster toCloudera Private Cloud Base 7. See the procedures provided by your database vendor.

MariaDB 5.5: http://mariadb.com/kb/en/mariadb/backup-and-restore-overview/
MySQL 5.5: http://dev.mysql.com/doc/refman/5.5/en/backup-and-recovery.html
MySQL 5.6: http://dev.mysql.com/doc/refman/5.6/en/backup-and-recovery.html
PostgreSQL 8.4: https://www.postgresql.org/docs/8.4/static/backup.html
PostgreSQL 9.2: https://www.postgresql.org/docs/9.2/static/backup.html
PostgreSQL 9.3: https://www.postgresql.org/docs/9.3/static/backup.html
Oracle 11gR2: https://docs.oracle.com/cd/E11882_01/backup.112/e10642/toc.htm
HyperSQL: http://hsqldb.org/doc/guide/management-chapt.html#mtc_backup

Restore Cloudera Manager Server

Use the backup of CDH that was taken before the upgrade to restore Cloudera Manager Server files and directories. Substitute the path to your backup directory for cm7_cdh6 in the following steps:

On the host where the Event Server role is configured to run, restore the Events Server directory from the CM 7/CDH 6 backup.

cp -rp /var/lib/cloudera-scm-eventserver /var/lib/cloudera-scm-eventserver-CM<ph outputclass="cdoc-specific-cm-from"/>-CDH<ph outputclass="cdoc-specific-cdh-from"/>
rm -rf /var/lib/cloudera-scm-eventserver/*
cp -rp /var/lib/cloudera-scm-eventserver_cm7_cdh6/* /var/lib/cloudera-scm-eventserver/

Remove the Agent runtime state. Run the following command on all hosts:
```
rm -rf /var/run/cloudera-scm-agent /var/lib/cloudera-scm-agent/response.avro
```
This command may return a message similar to: rm: cannot remove ‘/var/run/cloudera-scm-agent/process’: Device or resource busy. You can ignore this message.

On the host where the Service Monitor is running, restore the Service Monitor directory:

rm -rf /var/lib/cloudera-service-monitor/*
cp -rp /var/lib/cloudera-service-monitor_cm7_cdh6/* /var/lib/cloudera-service-monitor/

On the host where the Host Monitor is running, restore the Host Monitor directory:

rm -rf /var/lib/cloudera-host-monitor/*
cp -rp /var/lib/cloudera-host-monitor_cm7_cdh6/* /var/lib/cloudera-host-monitor/

Restore the Cloudera Navigator storage directory from the CM 7/CDH 6 backup.

rm -rf /var/lib/cloudera-scm-navigator/*
cp -rp /var/lib/cloudera-scm-navigator_cm7_cdh6/* /var/lib/cloudera-scm-navigator/

Start Cloudera Manager

Log in to the Cloudera Manager server host.
Start the Cloudera Manager Server.
```
sudo systemctl start cloudera-scm-server
```
Start the Cloudera Manager Agent.
Run the following commands on all cluster hosts:
```
sudo systemctl start cloudera-scm-agent
```
Start the Cloudera Management Service.
1. Log in to the Cloudera Manager Admin Console.
2. Select Clusters > Cloudera Management Service.
3. Select Actions > Start.
The cluster page may indicate that services are in bad health. This is normal.
Stop the cluster. In the Cloudera Manager Admin Console, click the Actions menu for the cluster and select Stop.

Roll Back ZooKeeper

Using the backup of Zookeeper that you created when backing up your CDH 6.x cluster, restore the contents of the dataDir on each ZooKeeper server. These files are located in a directory specified with the dataDir property in the ZooKeeper configuration. The default location is /var/lib/zookeeper. For example:
```
rm -rf /var/lib/zookeeper/*
cp -rp /var/lib/zookeeper_cm7_cdh6/* /var/lib/zookeeper/
```
Using the backup of Zookeeper that you created when backing up your CDH 6.x cluster, restore the contents of the Transaction Log Direcgtory on each ZooKeeper server. These files are located in a directory specified with the Transaction Log Direcgtory property in the ZooKeeper configuration. For example:
```
rm -rf /var/lib/zookeeper/*
cp -rp /var/lib/zookeeper_cm7_cdh6/* /var/lib/zookeeper/
```
Make sure that the permissions of all the directories and files are as they were before the upgrade.
Start ZooKeeper using Cloudera Manager.

Roll Back HDFS

You cannot roll back HDFS while high availability is enabled. The rollback procedure in this topic creates a temporary configuration without high availability. Regardless of whether high availability is enabled, follow the steps in this section.

Roll back all of the Journal Nodes. (Only required for clusters where high availability is enabled for HDFS). Use the JournalNode backup you created when you backed up HDFS before upgrading to Cloudera Private Cloud Base.
1. Log in to each Journal Node host and run the following commands:
```
rm -rf /dfs/jn/ns1/current/*
```
```
cp -rp <Journal_node_backup_directory>/ns1/current/* /dfs/jn/ns1/current/
```
2. Start the JournalNodes using Cloudera Manager:
  1. Go to the HDFS service.
  2. Select the Instances tab.
  3. Select all JournalNode roles from the list.
  4. Click Actions for Selected > Start.
Roll back all of the NameNodes. Use the NameNode backup directory you created before upgrading to Cloudera Private Cloud Base. (/etc/hadoop/conf.rollback.namenode) to perform the following steps on all NameNode hosts:
1. (Clusters with TLS enabled only) Edit the /etc/hadoop/conf.rollback.namenode/ssl-server.xml file on all NameNode hosts (located in the temporary rollback directory) and update the keystore passwords with the actual cleartext passwords.
  The passwords will have values that look like this:
```
<property>
    <name>ssl.server.keystore.password</name>
    <value>********</value>
  </property>
  <property>
    <name>ssl.server.keystore.keypassword</name>
    <value>********</value>
  </property>
```
2. (TLS only) Edit the /etc/hadoop/conf.rollback.namenode/ssl-server.xml file and remove the hadoop.security.credential.provider.path property.
3. (TLS only) Edit the /etc/hadoop/conf.rollback.namenode/ssl-server.xml file and update the ssl.server.keystore.location property:
```
# Original version of the keystore.location property:
<property>
  <name>ssl.server.keystore.location</name>
  <value>/var/run/cloudera-scm-agent/process/879-hdfs-NAMENODE/cm-auto-host_keystore.jks</value>
</property>
```
```
# New version of the keystore.location property:
<property>
  <name>ssl.server.keystore.location</name>
  <value>/etc/hadoop/conf.rollback.namenode/cm-auto-host_keystore.jks</value>
</property>
```
Edit the /etc/hadoop/conf.rollback.namenode/hdfs-site.xml file on all NameNode hosts and make the following changes:
1. Update the dfs.namenode.inode.attributes.provider.class property. If Sentry was installed prior to the upgrade, change the value of the property from org.apache.ranger.authorization.hadoop.RangerHdfsAuthorizer to "org.apache.sentry.hdfs.SentryINodeAttributesProvider. If Sentry was not installed, remove this property.
2. Change the path in the dfs.hosts property to the value shown in the example below. The file name, dfs_all_hosts.txt, may have been changed by a user. If so, substitute the correct file name.
```
# Original version of the dfs.hosts property:
<property>
<name>dfs.hosts</name>
<value>/var/run/cloudera-scm-agent/process/63-hdfs-NAMENODE/dfs_all_hosts.txt</value>
</property>
```
```
# New version of the dfs.hosts property:
<property>
<name>dfs.hosts</name>
<value>/etc/hadoop/conf.rollback.namenode/dfs_all_hosts.txt</value>
</property>
```
3. Remove the property that has the following value:
```
com.cloudera.navigator.audit.hdfs.HdfsAuditLoggerCdh5
```

Edit the /etc/hadoop/conf.rollback.namenode/core-site.xml and change the value of the net.topology.script.file.name property to /etc/hadoop/conf.rollback.namenode. For example:

# Original property
<property>
<name>net.topology.script.file.name</name>
<value>/var/run/cloudera-scm-agent/process/63-hdfs-NAMENODE/topology.py</value>
</property>

# New property
<property>
<name>net.topology.script.file.name</name>
<value>/etc/hadoop/conf.rollback.namenode/topology.py</value>
</property>

Edit the /etc/hadoop/conf.rollback.namenode/topology.py file and change the value of MAP_FILE to /etc/hadoop/conf.rollback.namenode. For example:
```
MAP_FILE = '/etc/hadoop/conf.rollback.namenode/topology.map'
```

(TLS-enabled clusters only) Run the following command:

sudo -u hdfs kinit hdfs/<NameNode Host name> -l 7d -kt /etc/hadoop/conf.rollback.namenode/hdfs.keytab

Run the following command:

sudo -u hdfs hdfs --config /etc/hadoop/conf.rollback.namenode namenode -rollback

Restart the NameNodes and JournalNodes using Cloudera Manager:
1. Go to the HDFS service.
2. Select the Instances tab, and then select all Failover Controller, NameNode, and JournalNode roles from the list.
3. Click Actions for Selected > Restart.
Rollback the DataNodes.
Use the DataNode rollback directory you created before upgrading to Cloudera Private Cloud Base (/etc/hadoop/conf.rollback.datanode) to perform the following steps on all DataNode hosts:
1. (Clusters with TLS enabled only) Edit the /etc/hadoop/conf.rollback.datanode/ssl-server.xml file on all DataNode hosts (Located in the temporary rollback directory.) and update the keystore passwords (ssl.server.keystore.password and ssl.server.keystore.keypassword) with the actual passwords.
  The passwords will have values that look like this:
```
<property>
    <name>ssl.server.keystore.password</name>
    <value>********</value>
  </property>
  <property>
    <name>ssl.server.keystore.keypassword</name>
    <value>********</value>
  </property>
```
2. (TLS only) Edit the /etc/hadoop/conf.rollback.datanode/ssl-server.xml file and update the ssl.server.keystore.location property:
```
# Original version of the keystore.location property:
<property>
  <name>ssl.server.keystore.location</name>
  <value>/var/run/cloudera-scm-agent/process/879-hdfs-NAMENODE/cm-auto-host_keystore.jks</value>
</property>
```
```
# New version of the keystore.location property:
<property>
  <name>ssl.server.keystore.location</name>
  <value>/etc/hadoop/conf.rollback.namenode/cm-auto-host_keystore.jks</value>
</property>
```
3. (TLS only) Edit the /etc/hadoop/conf.rollback.datanode/ssl-server.xml file and remove the hadoop.security.credential.provider.path property.
4. Edit the /etc/hadoop/conf.rollback.datanode/hdfs-site.xml file and remove the dfs.datanode.max.locked.memory property.
5. Run one of the following commands:
  - Run as root if the DataNodes use reserved ports.
    Search in the logs for completed rollback line. It will not be shown in the command line of the rollback.
  - If the DataNode is running with privileged ports (usually 1004 and 1006):
```
cd /etc/hadoop/conf.rollback.datanode
export HADOOP_SECURE_DN_USER=hdfs
export JSVC_HOME=/opt/cloudera/parcels/<parcel_filename>/lib/bigtop-utils
hdfs --config /etc/hadoop/conf.rollback.datanode datanode -rollback
```
  - If the DataNode is not running on privileged ports:
```
cd /etc/hadoop/conf.rollback.datanode
sudo hdfs --config /etc/hadoop/conf.rollback.datanode datanode -rollback
```
    You may see the following error after issuing these commands:
    ERROR datanode.DataNode: Exception in secureMain java.io.IOException: The path component: '/var/run/hdfs-sockets' in '/var/run/hdfs-sockets/dn' has permissions 0755 uid 39998 and gid 1006. It is not protected because it is owned by a user who is not root and not the effective user: '0'.
    The error message will also include the following command to run:
    chown root /var/run/hdfs-sockets
    After running this command, rerun the DataNode rollback command:
    sudo hdfs --config /etc/hadoop/conf.rollback.datanode datanode -rollback
    The DataNodes will now restart successfully.
  When the rolling back of the DataNodes is complete, terminate the console session by typing Control-C. Look for output from the command similar to the following that indicates when the DataNode rollback is complete:
```
Rollback of /dataroot/ycloud/dfs/dn/current/BP-<Block Group number> is complete
```
6. If High Availability for HDFS is enabled, restart the HDFS service. In the Cloudera Manager Admin Console, go to the HDFS service and select Actions > Restart.
7. If high availability is not enabled for HDFS, use the Cloudera Manager Admin Console to restart all NameNodes and DataNodes.
  1. Go to the HDFS service.
  2. Select the Instances tab
  3. Select all DataNode and NameNode roles from the list.
  4. Click Actions for Selected > Restart.
If high availability is not enabled for HDFS, roll back the Secondary NameNode.
1. (Clusters with TLS enabled only) Edit the /etc/hadoop/conf.rollback.secondarynamenode/ssl-server.xml file on all Secondary NameNode hosts (Located in the temporary rollback directory.) and update the keystore passwords with the actual cleartext passwords.
  The passwords will have values that look like this:
```
<property>
    <name>ssl.server.keystore.password</name>
    <value>********</value>
  </property>
  <property>
    <name>ssl.server.keystore.keypassword</name>
    <value>********</value>
  </property>
```
2. (TLS only) Edit the /etc/hadoop/conf.rollback.secondarynamenode/ssl-server.xml file and remove the hadoop.security.credential.provider.path property.
3. Log in to the Secondary NameNode host and run the following commands:
```
rm -rf /dfs/snn/*
cd /etc/hadoop/conf.rollback.secondarynamenode/
sudo -u hdfs hdfs --config /etc/hadoop/conf.rollback.secondarynamenode secondarynamenode -format
```
  When the rolling back of the Secondary NameNode is complete, terminate the console session by typing Control-C. Look for output from the command similar to the following that indicates when the Secondary NameNode rollback is complete:
```
2020-12-21 17:09:36,239 INFO namenode.SecondaryNameNode: Web server init done
```
Restart the HDFS service. Open the Cloudera Manager Admin Console, go to the HDFS service page, and select Actions > Restart.
The Restart Command page displays the progress of the restart. Wait for the page to display the Successfully restarted service message before continuing.

Start the HBase Service

Restart the HBase Service. Open the Cloudera Manager Admin Console, go to the HBase service page, and select Actions > Start.

If you have configured any HBase coprocessors, you must revert them to the versions used before the upgrade.

If CDP 7.x HBase Master was started after the upgrade and there was any ongoing (or stuck) HBase Master Procedure present in the HBase Master before stopping the CDP 7 Cluster, then it is expected for the CDH 6 HBase Master to fail with warnings and errors in the role log from the classes like 'ProcedureWALFormatReader' and 'WALProcedureStore' or 'TransitRegionStateProcedure'. These errors mean that the HBase Master Write-Ahead Log files are incompatible with the CDH 6 HBase version. The only way to fix this problem is to sideline the log files (all the files placed under /hbase/MasterProcWALs by default), then restart the HBase Master. After the HBase Master has started, Use the HBCK command to find out if there are any inconsistencies that will need to be fixed manually.

You my encounter other errors when starting HBase (for example, replication-related problems, region assignment related issues, and meta region assignment problems). In this case you should delete the znode in ZooKeeper and then start HBase again. (This will delete replication peer information and you will need to re-configure your replication schedules.):

In Cloudera Manager, look up the value of the zookeeper.znode.parent property. The default value is /hbase.
Connect to the ZooKeeper ensemble by running the following command from any HBase gateway host:
```
zookeeper-client -server zookeeper_ensemble
```
To find the value to use for zookeeper_ensemble, open the /etc/hbase/conf.cloudera.<HBase service name>/hbase-site.xml file on any HBase gateway host. Use the value of the hbase.zookeeper.quorum property.
note
If you have deployed a secure cluster, you must connect to ZooKeeper using a client jaas.conf file. You can find such a file in an HBase process directory (/var/run/cloudera-scm-agent/process/). Specify the jaas.conf using the JVM flags by running the following commands in the ZooKeeper client:
```
CLIENT_JVMFLAGS=
 "-Djava.security.auth.login.config=/var/run/cloudera-scm-agent/process/HBase_process_directory/jaas.conf"

zookeeper-client -server <zookeeper_ensemble>
```
The ZooKeeper command-line interface opens.
Enter the following command:
```
rmr /hbase
```
After HBase is healthy, make sure you restore the states of the Balancer and Normalizer (enable them if they were enabled before the rollback). Also re-enable the Merge and Split operations you disabled before the rollback to avoid the Master Procedure incompatibility problem. Run the following commands in HBase Shell:
```
balance_switch true 
normalizer_switch true 
splitormerge_switch 'SPLIT', true 
splitormerge_switch 'MERGE', true 
```

Fixing tableinfo file format

When you are rolling back from CDP Private Cloud Base 7.1.8 to CDH 6 if you encounter a change in the tableinfo file name format from the new tableinfo file name that was created during the 7.1.8 upgrade can prevent HBase from functioning normally.

After the rollback, if HDFS rollback was not successful and Hbase is unable to read the tableinfo files then use the HBCK2 tool to verify the list of tableinfo files that need to be fixed.

Follow these steps to execute the HBCK2 command on the HBCK2 tool to fix the tableinfo file format:

Contact Cloudera support to request the latest version of HBCK2 tool.
Use the following HBCK2 command and run the HBCK2 tool without the –fix option:
```
hbase --config /path/to/client/conf hbck -j 
~/path/to/hbck/hbase-hbck2-1.0.0-<build>.jar shortenTableinfo 
```
For example:
```
hbase --config /etc/hbase/conf hbck -j
~/hbase-operator-tools/hbase-hbck2/target/hbase-hbck2-1.0.0-SNAPSHOT.jar shortenTableinfo
```
The command displays the following message and the list of files to be fixed:
Found the following tableinfo file names containing file size
If the list is empty, no additional steps are needed. Go to Step 11.

Use the following HBCK2 command and run the HBCK2 tool with the –fix option:

hbase --config /etc/hbase/conf hbck -j
~/hbase-operator-tools/hbase-hbck2/target/hbase-hbck2-1.0.0-SNAPSHOT.jar shortenTableinfo –fix

Check the output and verify whether all the tableinfo files are fixed.

Restore CDH Databases

Restore the following databases from the CDH 6 backups:

Hive Metastore
Hue
Oozie
Sentry Server

The steps for backing up and restoring databases differ depending on the database vendor and version you select for your cluster and are beyond the scope of this document.

See the following vendor resources for more information:

MariaDB 5.5: http://mariadb.com/kb/en/mariadb/backup-and-restore-overview/
MySQL 5.5: http://dev.mysql.com/doc/refman/5.5/en/backup-and-recovery.html
MySQL 5.6: http://dev.mysql.com/doc/refman/5.6/en/backup-and-recovery.html
MySQL 5.7: http://dev.mysql.com/doc/refman/5.7/en/backup-and-recovery.html
PostgreSQL 8.4: https://www.postgresql.org/docs/8.4/static/backup.html
PostgreSQL 9.2: https://www.postgresql.org/docs/9.2/static/backup.html
PostgreSQL 9.3: https://www.postgresql.org/docs/9.3/static/backup.html
Oracle 11gR2: https://docs.oracle.com/cd/E11882_01/backup.112/e10642/toc.htm

Start the Sentry Service

Roll Back Cloudera Search

Start the HDFS, Zookeeper and Sentry services.
Delete the instancedir created during the upgrade process:
1. If the cluster is secured with Kerberos, run this command Otherwise skip this step.
```
export ZKCLI_JVM_FLAGS="-Djava.security.auth.login.config=~/solr-jaas.conf 
-DzkACLProvider=org.apache.solr.common.cloud.ConfigAwareSaslZkACLProvider" 
```
2. ```
sudo -u solr solrctl instancedir --delete localFSTemplate 
```
3. Start the Solr service.
note
If the state of one or more Solr core is down and the Solr log contains an org.apache.lucene.store.LockObtainFailedException: Lock obtain timed out: org.apache.solr.store.hdfs.HdfsLockFactory error message, it is necessary to clean up the HDFS locks in the index directories.
For each of the affected Solr nodes:
1. 1. Stop the Solr node using Cloudera Manager.
2. 2. Remove the HdfsDirectory<id>-write.lockfile from the index directory.
```
hdfs dfs -rm "/solr/<collection_name>/<core>/data/<index_directory_name>/HdfsDirectory@ <hex_id> lockFactory=org.apache.solr.store.hdfs.HdfsLockFactory@<hex_id>-write.lock"
```
  For example:
```
hdfs dfs -rm "/solr/testCollection/core_node1/data/index/HdfsDirectory@5d07feac lockFactory=org.apache.solr.store.hdfs.HdfsLockFactory@7df08aad-write.lock" 
```
3. 3. Start the Solr node using Cloudera Manager.

Roll Back Hue

Restore the file, app.reg, from your backup:

Parcel installations

rm -rf /opt/cloudera/parcels/CDH/lib/hue/app.reg
cp -rp app.reg_cm7_cdh6_backup /opt/cloudera/parcels/CDH/lib/hue/app.reg

Package Installations

rm -rf /usr/lib/hue/app.reg
cp -rp app.reg_cm7_cdh6_backup /usr/lib/hue/app.reg

Roll Back Kafka

A Cloudera Private Cloud Base 7 cluster that is running Kafka can be rolled back to the previous CDH5/CDK versions as long as theinter.broker.protocol.version and log.message.format.version properties have not been set to the new version or removed from the configuration.

To perform the rollback using Cloudera Manager:

Activate the previous CDK parcel. Please note, that when rolling back Kafka from CDP Private Cloud Base 7 to CDH 6/CDK, the Kafka cluster will restart. Rolling restart is not supported for this scenario. See Activating a Parcel.
Remove the following properties from the Kafka Broker Advanced Configuration Snippet (Safety Valve) configuration property.
- Inter.broker.protocol.version
- log.message.format.version

Deploy the Client Configuration

On the Cloudera Manager Home page, click the Actions menu and select Deploy Client Configuration.
Click Deploy Client Configuration.

Restart the Cluster

On the Cloudera Manager Home page, click the Actions menu and select Restart.
Click Restart that appears in the next screen to confirm. If you have enabled high availability for HDFS, you can choose Rolling Restart instead to minimize cluster downtime. The Command Details window shows the progress of stopping services.
When All services successfully started appears, the task is complete and you can close the Command Details window.

Roll Back Cloudera Navigator Encryption Components

If you are rolling back any encryption components (Key Trustee Server, Key Trustee KMS, HSM KMS, Key HSM, or Navigator Encrypt), first refer to:

Roll Back Key Trustee Server

To roll back Key Trustee Server, replace the currently used parcel (for example, the parcel for version 7.1.4) with the parcel for the version to which you wish to roll back (for example, version 5.14.0). See Parcels for detailed instructions on using parcels.

The Keytrustee Server 7.x upgrades the bundled Postgres engine from version 9.3 to 12.1. The upgrade happens automatically, however, downgrading to CDH 6 requires manual steps to roll back the database engine to version 9.3. Because the previously upgraded database is left unchanged, the database server will fail start. Follow these steps to recreate the Postgres 9.3 compatible database:

Open the Cloudera Manager Admin Console and go to the Key Trustee Server service. If you see that Key Trustee Server has stale configurations, click the yellow or blue button and follow the prompts.
Make sure that the Keytrustee Server database roles are stopped. Then rename the folder containing Keytrustee Postgres database data (both on master and slave hosts):
```
mv /var/lib/keytrustee/db /var/lib/keytrustee/db-12_1
```
Open the Cloudera Manager Admin Console and go to the Key Trustee Server service.
Select the Instances tab.
Select the Active Database role type.
Click Actions for Selected > Set Up the Key Trustee Server Database.
Click Set Up the Key Trustee Server Database to confirm.
Cloudera Manager sets up the Key Trustee Server database.
Start the Active Database role in Cloudera Manager by clicking Actions for Selected > Start.
Click Start to confirm.
On the master KTS node: running as user keytrustee, restore the keytrustee database from the dump created during the upgrade by running the following commands:
```
sudo -su keytrustee
cd
export HOME=/opt/cloudera/parcels/KEYTRUSTEE_SERVER
export JAVA_HOME=... # Set this to your Java Home folder
export PATH="/opt/cloudera/parcels/KEYTRUSTEE_SERVER/bin:/opt/cloudera/parcels/KEYTRUSTEE_SERVER/PG_DB/opt/postgres/9.3/bin:$PATH"
source /opt/cloudera/parcels/KEYTRUSTEE_SERVER/meta/keytrustee_env.sh
dropdb -p 11381 keytrustee
```
If you see the message: could not change directory to "/root: Permission denied on the console, run the following command to check the exit code of the last command:
```
$? 
```
You can use the exit code to debug any issues.
Run the following command to import a database dump that was created during upgrade:
```
psql -p 11381 postgres -f /var/lib/keytrustee/.keytrustee/kt93dump.pg
```
Enable synchronous replication by navigating to KTS > Actions > Enable Synchronous Replication in HA Mode.
Start the Passive Database instance: select the Passive Database, click Actions for Selected > Start.
In the Cloudera Manager Admin Console, start the active KTS instance.
In the Cloudera Manager Admin Console, start the passive KTS instance.

Start the Key Management Server

Restart the Key Management Server. Open the Cloudera Manager Admin Console, go to the KMS service page, and select Actions > Start.

Roll Back Key HSM

To roll back Key HSM:

Install the version of Navigator Key HSM to which you wish to roll back
Install the Navigator Key HSM package using yum:
```
sudo yum downgrade keytrustee-keyhsm
```
Cloudera Navigator Key HSM is installed to the /usr/share/keytrustee-server-keyhsm directory by default.
Rename Previously-Created Configuration Files
For Key HSM major version rollbacks, previously-created configuration files do not authenticate with the HSM and Key Trustee Server, so you must recreate these files by re-executing the setup and trust commands. First, navigate to the Key HSM installation directory and rename the applications.properties, keystore, and truststore files:
```
cd /usr/share/keytrustee-server-keyhsm/
mv application.properties application.properties.bak
mv keystore keystore.bak
mv truststore truststore.bak
```
Initialize Key HSM
Run the service keyhsm setup command in conjunction with the name of the target HSM distribution:
```
sudo service keyhsm setup [keysecure|thales|luna]
```
For more details, see Initializing Navigator Key HSM.
Establish Trust Between Key HSM and the Key Trustee Server
The Key HSM service must explicitly trust the Key Trustee Server certificate (presented during TLS handshake). To establish this trust, run the following command:
```
sudo keyhsm trust /path/to/key_trustee_server/cert
```
For more details, see Establish Trust from Key HSM to Key Trustee Server.
Start the Key HSM Service
Start the Key HSM service:
```
sudo service keyhsm start
```
Establish Trust Between Key Trustee Server and Key HSM
Establish trust between the Key Trustee Server and the Key HSM by specifying the path to the private key and certificate:
```
sudo ktadmin keyhsm --server https://keyhsm01.example.com:9090 \
--client-certfile /etc/pki/cloudera/certs/mycert.crt \
--client-keyfile /etc/pki/cloudera/certs/mykey.key --trust
```
For a password-protected Key Trustee Server private key, add the --passphrase argument to the command (enter the password when prompted):
```
sudo ktadmin keyhsm --passphrase \
--server https://keyhsm01.example.com:9090 \
--client-certfile /etc/pki/cloudera/certs/mycert.crt \
--client-keyfile /etc/pki/cloudera/certs/mykey.key --trust
```
For additional details, see Integrate Key HSM and Key Trustee Server.
Remove Configuration Files From Previous Installation
After completing the rollback, remove the saved configuration files from the previous installation:
```
cd /usr/share/keytrustee-server-keyhsm/
rm application.properties.bak
rm keystore.bak
rm truststore.bak
```

Roll Back Key Ranger KMS Parcels

Enable the desired parcel that you wish to roll back to (for example, version 6.3.4 of Key Trustee KMS). See Parcels for detailed instructions on using parcels. See Parcels for detailed instructions on using parcels.

Roll Back HSM KMS Parcels

To roll back the HSM KMS parcels, replace the currently used parcel (for example, the parcel for version 6.0.0) with the parcel for the version to which you wish to roll back (for example, version 5.14.0). See Parcels for detailed instructions on using parcels.

See Upgrading HSM KMS Using Packages for detailed instructions on using packages.

Roll Back Navigator Encrypt

To roll back Cloudera Navigator Encrypt:

If you have configured and are using an RSA master key file with OAEP padding, then you must revert this setting to its original value:
```
navencrypt key --change
```
Stop the Navigator Encrypt mount service:
```
sudo /etc/init.d/navencrypt-mount stop
```
Confirm that the mount-stop command completed:
```
sudo /etc/init.d/navencrypt-mount status
```

Backup the NavEncrypt control directory:

sudo mkdir navencryptBAK
sudo cp -rp /etc/navencrypt/ navencryptBAK/

Clean the dkms/navencryptfs directory:

sudo rm -rf /var/lib/dkms/navencryptfs/

If rolling back to a release lower than NavEncrypt 6.2:
1. Print the existing ACL rules and save that output to a file:
```
sudo navencrypt acl --print+ vim acls.txt
```
2. Delete all existing ACLs, for example, if there are a total of 7 ACL rules run:
```
sudo navencrypt acl --del --line=1,2,3,4,5,6,7
```
To fully downgrade Navigator Encrypt, manually downgrade all of the associated Navigator Encrypt packages (in the order listed):
1. navencrypt
2. navencrypt-kernel-module (Only required for operating systems other than SLES)
3. cloudera-navencryptfs-kmp (Only required for the SLES operating system)
4. libkeytrustee
If rolling back to a release less than NavEncrypt 6.2
1. Reapply the ACL rules:
```
sudo navencrypt acl --add --file=acls.txt
```
2. Recompute process signatures:
```
sudo navencrypt acl --update
```
Restart the Navigator Encrypt mount service
```
sudo /etc/init.d/navencrypt-mount start
```

(Optional) Cloudera Manager Rollback Steps

After you complete the rollback steps, your cluster is using Cloudera Manager 7 to manage your CDH 6 or CDH 6 cluster. You can continue to use Cloudera Manager 7 to manage your CDH 6 cluster, or you can downgrade to Cloudera Manager 6 by following these steps:

Stop Cloudera Manager

Stop the Cloudera Management Service.
1. Log in to the Cloudera Manager Admin Console.
2. Select Clusters > Cloudera Management Service.
3. Select Actions > Stop.
Stop the Cloudera Manager Server.
```
sudo systemctl stop cloudera-scm-server
```
Hard stop the Cloudera Manager agents. Run the following command on all hosts:
```
sudo systemctl stop cloudera-scm-supervisord.service
```
Back up the repository directory. You can create a top-level backup directory and an environment variable to reference the directory using the following commands. You can also substitute another directory path in the backup commands below:
```
export CM_BACKUP_DIR="`date +%F`-CM"
mkdir -p $CM_BACKUP_DIR
```

Back up the existing repository directory.

RHEL / CentOS

sudo -E tar -cf $CM_BACKUP_DIR/repository.tar /etc/yum.repos.d

SLES

sudo -E tar -cf $CM_BACKUP_DIR/repository.tar /etc/zypp/repos.d

Ubuntu

sudo -E tar -cf $CM_BACKUP_DIR/repository.tar /etc/apt/sources.list.d

Restore the Cloudera Manager 6 Repository Files

Copy the repository directory from the backup taken before upgrading to Cloudera Manager 7.x.

rm -rf /etc/yum.repos.d/*
tar -xf cm6cdh6_backedUp_dir/repositary.tar -C CM6CDH6/
cp -rp /etc/yum.repos.d_cm6cdh6/* /etc/yum.repos.d/

Restore Packages

Run the following commands on all hosts:

Operating System Command

RHEL

Operating System	Command
RHEL	`sudo yum remove cloudera-manager-daemons cloudera-manager-agent` `sudo yum clean all sudo yum install cloudera-manager-agent`
SLES	`sudo zypper remove cloudera-manager-daemons cloudera-manager-agent` `sudo zypper refresh -s sudo zypper install cloudera-manager-agent`
Ubuntu or Debian	`sudo apt-get purge cloudera-manager-daemons cloudera-manager-agent` `sudo apt-get update sudo apt-get install cloudera-manager-agent`

sudo yum remove cloudera-manager-daemons cloudera-manager-agent

sudo yum clean all
sudo yum install cloudera-manager-agent

SLES

sudo zypper remove cloudera-manager-daemons cloudera-manager-agent

sudo zypper refresh -s
sudo zypper install cloudera-manager-agent

Ubuntu or Debian

sudo apt-get purge cloudera-manager-daemons cloudera-manager-agent

sudo apt-get update
sudo apt-get install cloudera-manager-agent

Run the following commands on the Cloudera Manager server host:

Operating System Command

RHEL

Operating System	Command
RHEL	`sudo yum remove cloudera-manager-server` `sudo yum install cloudera-manager-server`
SLES	`sudo zypper remove cloudera-manager-server` `sudo zypper install cloudera-manager-server`
Ubuntu or Debian	`sudo apt-get purge cloudera-manager-server` `sudo apt-get install cloudera-manager-server`

sudo yum remove cloudera-manager-server

sudo yum install cloudera-manager-server

SLES

sudo zypper remove cloudera-manager-server

sudo zypper install cloudera-manager-server

Ubuntu or Debian

sudo apt-get purge cloudera-manager-server

sudo apt-get install cloudera-manager-server

Restore Cloudera Manager Databases

Restore the Cloudera Manager databases from the backup of Cloudera Manager that was taken before upgrading to Cloudera Manager 7. See the procedures provided by your database vendor.

These databases include the following:

Cloudera Manager Server
Reports Manager
Navigator Audit Server
Navigator Metadata Server
Activity Monitor (Only used for MapReduce 1 monitoring).

MariaDB 5.5: http://mariadb.com/kb/en/mariadb/backup-and-restore-overview/
MySQL 5.5: http://dev.mysql.com/doc/refman/5.5/en/backup-and-recovery.html
MySQL 5.6: http://dev.mysql.com/doc/refman/5.6/en/backup-and-recovery.html
PostgreSQL 8.4: https://www.postgresql.org/docs/8.4/static/backup.html
PostgreSQL 9.2: https://www.postgresql.org/docs/9.2/static/backup.html
PostgreSQL 9.3: https://www.postgresql.org/docs/9.3/static/backup.html
Oracle 11gR2: https://docs.oracle.com/cd/E11882_01/backup.112/e10642/toc.htm
HyperSQL: http://hsqldb.org/doc/guide/management-chapt.html#mtc_backup

Here is an sample command to restore a MySQL database:

mysql -u username -ppassword --host=hostname cm < backup.sql

Restore Cloudera Manager Server

Use the backup of Cloudera Manager 6.x taken before upgrading to Cloudera Manager 7.x for the following steps:

If you used the backup commands provided in Step 2: Backing Up Cloudera Manager 6, extract the Cloudera Manager 6 backup archives you created:
```
tar -xf CM6CDH6/cloudera-scm-agent.tar -C CM6CDH6/
tar -xf CM6CDH6/cloudera-scm-server.tar -C CM6CDH6/
```

On the host where the Event Server role is configured to run, restore the Events Server directory from the Cloudera Manager 6 backup.

cp -rp /var/lib/cloudera-scm-eventserver /var/lib/cloudera-scm-eventserver-CM
rm -rf /var/lib/cloudera-scm-eventserver/*
cp -rp /var/lib/cloudera-scm-eventserver_cm6cdh6/* /var/lib/cloudera-scm-eventserver/

Remove the Agent runtime state. Run the following command on all hosts:
```
rm -rf /var/run/cloudera-scm-agent /var/lib/cloudera-scm-agent/response.avro
```

On the host where the Service Monitor is running, restore the Service Monitor directory:

rm -rf /var/lib/cloudera-service-monitor/*
cp -rp /var/lib/cloudera-service-monitor_cm6cdh6/* /var/lib/cloudera-service-monitor/

On the host where the Host Monitor is running, restore the Host Monitor directory:

rm -rf /var/lib/cloudera-host-monitor/*
cp -rp /var/lib/cloudera-host-monitor_cm6cdh6/* /var/lib/cloudera-host-monitor/

Restore the Cloudera Navigator Solr storage directory from the CM6/CDH6 backup.

rm -rf /var/lib/cloudera-scm-navigator/*
cp -rp /var/lib/cloudera-scm-navigator_cm6cdh6/* /var/lib/cloudera-scm-navigator/

On the Cloudera Manager Server, restore the /etc/cloudera-scm-server/db.properties file.

rm -rf /etc/cloudera-scm-server/db.properties
cp -rp cm6cdh6/etc/cloudera-scm-server/db.properties /etc/cloudera-scm-server/db.properties

On each host in the cluster, restore the /etc/cloudera-scm-agent/config.ini file from your backup.

rm -rf /etc/cloudera-scm-agent/config.ini
cp -rp cm6cdh6/etc/cloudera-scm-agent/config.ini /etc/cloudera-scm-agent/config.ini

Start the Cloudera Manager Server and Agents

Start the Cloudera Manager Server.
```
sudo systemctl start cloudera-scm-server
```

Hard Restart the Cloudera Manager Agent.

RHEL 7, SLES 12, Ubuntu 18.04 and higher

sudo systemctl stop cloudera-scm-supervisord.service
sudo systemctl restart cloudera-scm-agent

Start the Cloudera Management Service.
1. Log in to the Cloudera Manager Admin Console.
2. Select Clusters > Cloudera Management Service.
3. Select Actions > Start.