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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-718) configuration parameter to prevent accidental formatting of HDFS filesystem
Date Thu, 05 Nov 2009 00:01:32 GMT

    [ https://issues.apache.org/jira/browse/HDFS-718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12773717#action_12773717
] 

dhruba borthakur commented on HDFS-718:
---------------------------------------

Hi Rajiv: no software can ensure that the administrator not change the config...this is an
operational procedure. But don't you agree that it is better if we can ensure that multiple
administrative-failures have to happen before the cluster can be reformatted? In this case,
the "confirm prompt" together with the config value makes the protection slightly more secure,
isn't it?

> configuration parameter to prevent accidental formatting of HDFS filesystem
> ---------------------------------------------------------------------------
>
>                 Key: HDFS-718
>                 URL: https://issues.apache.org/jira/browse/HDFS-718
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>    Affects Versions: 0.22.0
>         Environment: Any
>            Reporter: Andrew Ryan
>            Assignee: Andrew Ryan
>            Priority: Minor
>         Attachments: HDFS-718.patch.txt
>
>
> Currently, any time the NameNode is not running, an HDFS filesystem will accept the 'format'
command, and will duly format itself. There are those of us who have multi-PB HDFS filesystems
who are really quite uncomfortable with this behavior. There is "Y/N" confirmation in the
format command, but if the formatter genuinely believes themselves to be doing the right thing,
the filesystem will be formatted.
> This patch adds a configuration parameter to the namenode, dfs.namenode.support.allowformat,
which defaults to "true," the current behavior: always allow formatting if the NameNode is
down or some other process is not holding the namenode lock. But if dfs.namenode.support.allowformat
is set to "false," the NameNode will not allow itself to be formatted until this config parameter
is changed to "true".
> The general idea is that for production HDFS filesystems, the user would format the HDFS
once, then set dfs.namenode.support.allowformat to "false" for all time.
> The attached patch was generated against trunk and +1's on my test machine. We have a
0.20 version that we are using in our cluster as well.

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