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https://issues.apache.org/jira/browse/HADOOP-7198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13451374#comment-13451374
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Harsh J commented on HADOOP-7198:
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bq. Any port that is picked is going to conflict with something when talking
above the 1k port line.
For Linux this may not hold true though, it seems to limit the ephemeral range
from 32k onwards these days. But yeah, thats non-standard.
> 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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