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From Suresh Srinivas <sur...@hortonworks.com>
Subject Re: Significance of PID files
Date Mon, 07 Jul 2014 17:25:58 GMT
When a daemon process is started, the process ID of the process is captured
in a pid file. It is used for following purposes:
- During a daemon startup, the existence of pid file is used to determine
that the process is already running.
- When a daemon is stooped, hadoop scripts sends kill TERM signal  to the
process ID captured in pid file for graceful shutdown. After a timeout, if
the process still exists, "kill -9" is sent for forced shutdown.

For more details, see the relevant code in
http://svn.apache.org/repos/asf/hadoop/common/trunk/hadoop-common-project/hadoop-common/src/main/bin/hadoop-daemon.sh




On Fri, Jul 4, 2014 at 10:00 AM, Vijaya Narayana Reddy Bhoomi Reddy <
vijay.bhoomireddy@gmail.com> wrote:

> Hi,
>
> Can anyone please explain the significance of the pid files in Hadoop i.e.
> purpose and usage etc?
>
> Thanks & Regards
> Vijay
>



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