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https://issues.apache.org/jira/browse/HDFS-12420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16165177#comment-16165177
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Arpit Agarwal edited comment on HDFS-12420 at 9/13/17 7:43 PM:
---------------------------------------------------------------

Allen, thanks for bringing up the automation concern. We certainly don't want 
to break any deployment scripts. This patch will not break scripted deployment 
of new clusters since it eliminates the prompt completely.

Formatting clusters with pre-existing data was a bad idea in the first place. 
It deletes the NameNode metadata and leaves the cluster in an unusable state 
since DataNodes cannot connect anymore. I don't think any existing automation 
can depend on this behavior since it is functionally broken.

That said, if you have examples of automated deployments that will be broken by 
this change and that we haven't thought of, we can abandon the idea.


was (Author: arpitagarwal):
Allen, thanks for bringing up the automation concern. We certainly don't want 
to break any deployment scripts. This patch will not break scripted deployment 
of new clusters since it eliminates the prompt completely.

Formatting clusters with pre-existing data was a bad idea in the first place. 
It deletes the NameNode metadata and leaves the cluster in an unusable state 
since DataNodes cannot connect anymore. I don't think any existing automation 
can depend on this behavior since it is functionally broken.

> Disable Namenode format when data already exists
> ------------------------------------------------
>
>                 Key: HDFS-12420
>                 URL: https://issues.apache.org/jira/browse/HDFS-12420
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: Ajay Kumar
>            Assignee: Ajay Kumar
>         Attachments: HDFS-12420.01.patch, HDFS-12420.02.patch
>
>
> Disable NameNode format to avoid accidental formatting of Namenode in 
> production cluster. If someone really wants to delete the complete fsImage, 
> they can first delete the metadata dir and then run {code} hdfs namenode 
> -format{code} manually.



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