Downgrade Ambari 2.7.3 to 2.62 on New HDP 2.6.4 Installatioin

[#1]

I would like to downgrade Ambari server (from 2.7.3 to 2.6.2). This is a new installation and since Ambari was never upgraded, there are no database back up files (as referenced here: https://community.hortonworks.com/questions/175812/downgrade-procedure-from-ambari-version-2610-to-l.... Therefore, I modified the instructions as follows (omitting the old database import steps and re-running ambari-server setup). Will this work without negatively affecting the other HDP 2.6.4 components? If not, is there a procedure to downgrade Ambari in a new installation?

1. Stop the ambari-server.
# ambari-server stop

2. Stop all the ambari-agents on all hosts.
# ambari-agent stop

3. Download the ambari.repo of the downgraded version on all agent hosts and ambari server host.

Example:

# wget -nv http://public-repo-1.hortonworks.com/ambari/centos7/2.x/updates/2.4.2.0/ambari.repo -O /etc/yum.repos.d/ambari.repo
	

4. (omitting this step) Then take a backup of "/etc/ambari-server/conf" and "/etc/ambari-agent/conf" directories (for backup).

5. Erase the ambari Binaries from Ambari Server and Ambari Agent hosts like (basically cleaning up the Ambari Server and agent binaries)

yum remove ambari-server ambari-agent

rm -f /usr/sbin/ambari*

rm -f /usr/lib/python2.6/site-packages/ambari_commons

rm -f /usr/lib/python2.6/site-packages/ambari_server

rm -rf /usr/lib/python2.6/site-packages/resource_management

rm -rf /usr/lib/python2.6/site-packages/ambari_jinja2

rm -f /usr/lib/python2.7/site-packages/ambari_commons

rm -f /usr/lib/python2.7/site-packages/ambari_server

rm -rf /usr/lib/python2.7/site-packages/resource_management

rm -rf /usr/lib/python2.7/site-packages/ambari_jinja2

rm -rf /var/lib/ambari-server

rm -rf /var/lib/ambari-agent/

rm -rf /usr/lib/ambari-agent/

rm -rf /usr/lib/ambari-server/

6. Perform yum cleanup

# yum clean all

7. (omitting this step) Import the OLD Database Dump of previous ambari version to the Database. (for example ambari 2.4.2 DB dump)

# su postgres -c 'psql -c "drop database ambari" '

# su postgres -c 'psql -c "create database ambari" '

# su postgres -c 'psql -f ./ambari_old_242.sql -d ambari'

8. Install ambari-server and ambari agents (agent on all hosts)

# yum install ambari-server ambari-agent -y (On Ambari Server)

# yum install ambari-agent -y (On all cluster nodes)

9. Rerun ambari-server setup

# ambari-server setup

10. Start ambari agents and ambari server.

# ambari-server start

# ambari-agent start

[#2 · Accepted solution]

@sean1 

As you mentioned that .  "This is a new installation and since Ambari was never upgraded,"  ....  "there are no database back up files"

1. If this a new installation then what is the reason for downgrading ambari? 

    If ambari was never upgraded  (as it is a new installation) then what is the need to downgrade it ?

2. If you do not have the Ambari DB backup then you can not recover the cluster installation even if you installed the Ambari 2.6.2  (So backup is must)

[#3]

@jsensharma,

Thank you very much for your prompt reply and clear answer.

The reason for wanting to downgrade was to avoid a complete re-install (for logistical reasons). The version should have been 2.6.2.0 per spec request.