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https://issues.apache.org/jira/browse/HADOOP-7198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14659152#comment-14659152
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Jonathan Kelly commented on HADOOP-7198:
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Any chance we could start this long dead conversation back up? It looks like
similar changes were made somewhat recently in HBASE-10123.
> Hadoop defaults for web UI ports often fall smack in the middle of Linux
> ephemeral port range
> ---------------------------------------------------------------------------------------------
>
> Key: HADOOP-7198
> URL: https://issues.apache.org/jira/browse/HADOOP-7198
> Project: Hadoop Common
> Issue Type: Wish
> Reporter: Philip Zeyliger
> Priority: Trivial
>
> It turns out (see http://en.wikipedia.org/wiki/Ephemeral_port and
> /proc/sys/net/ipv4/ip_local_port_range) that when you bind to port 0, Linux
> chooses an ephemeral port. On my default-ridden Ubuntu Maverick box and on
> CentOS 5.5, that range is 32768-61000. So, when HBase binds to 60030 or when
> mapReduce binds to 50070, there's a small chance that you'll conflict with,
> say, an FTP session, or with some other Hadoop daemon that's had a listening
> address configured as :0.
> I don't know that there's a practical resolution here, since changing the
> defaults seems like an ill-fated effort, but if you have any ephemeral port
> use, you can run into this. We've now run into it once.
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