@moubaba
I know its a dompting task but unfortunately, I could create a link by an article for Jordan Moore let me try to elaborate.
Simple advice always run a crontab job to dump all your databases or at leat the ambari DB nightly !
Firstly Ambari doesn't control any data residing on the data nodes, so you should be safe there. Stop all ambari-agents in the cluster, maybe even uninstalling it so as to let all the Hadoop components remain running "in the dark".
Install and set up a new Ambari server, add a cluster but do not register any hosts [very important]. If you uninstalled the ambari -agents on the nodes please do re-install ensure the ambari-server and the agents are the same versions.
Do the below if you removed Ambari and the agents
# yum repolist
On the ambari-server
# yum install ambari-server
# yum install ambari-agent
On the other hosts
# yum install ambari-agent
Reconfigure manually the ambari agents [ambari-agent.ini] to point at the new Ambari server address, and start them.
Add the hosts in the Ambari server UI, selecting "manual registration" option the hosts register successfully since the agents are running a point to note install and configure an ambari-agent on the Ambari server to point to itself !!!!
After this, you get the option of installing clients and servers.
Now, you could try to "reinstall" what is already there, but you might want to deselect all the servers on the data node column.
In theory, it will try to perform OS package installation, and say that the service already exists, and doesn't error out. If it does error, then restart the install process, but deselect everything. At which point, it should continue and now you have Ambari back up and running with all the hosts monitored, just with no processes to configure.
To add the services back, you would need to use the Ambari REST API to add back in the respective Services, Components, and Host Components that you have running on the cluster. If you can't remember all the Services, Components, and Host Components then go to each host and do a process check to see what's running.
Variables
export AMBARI_USER=admin
export AMBARI_PASSWD=admin
export CLUSTER_NAME=<New_Cluster_name>
export AMBARI_SERVER=<Your_new_ambari_server_FQDN>
export AMBARI_PORT=8080
List all services related to hive
In the below example I am listing all hive components
curl -u $AMBARI_USER:$AMBARI_PASSWD -H 'X-Requested-By: ambari' -X GET "http://$AMBARI_SERVER:$AMBARI_PORT/api/v1/clusters/$CLUSTER_NAME/services/HIVE"
Adding back pig
curl -k -u $AMBARI_USER:$AMBARI_PASSWD -H "X-Requested-By:ambari" -i -X POST -d '{"RequestInfo":{"context":"Install PIG"}, "Body":{"HostRoles":{"state":"INSTALLED"}}}' 'http://'$AMBARI_SERVER':$AMBARI_PORT/api/v1/clusters/'$CLUSTER_NAME'/services/PIG/components/PIG'
This is the time to get your hands dirty 🙂 This isn't production so it should train you for a real situation
Happy hadooping !!
