When setting up passwordless ssh on a cluster, its clear that the namenode
needs to be able to ssh into task trackers to start/stop nodes and restart
the cluster.

What else is passwordless SSH used for?  Do TaskTrackers/DataNodes ever SSH
into each other horizontally ? Or is SSH only used for one-way nn to tt
operations?

--
Jay Vyas
http://jayunit100.blogspot.com

The JobTracker will also SSH in to start TaskTracker's.

So basically, the masters need SSH to any slave(s) you define.  The slave
nodes (DN, TT) do not need SSH to each other.
On Tue, Feb 5, 2013 at 5:06 PM, Jay Vyas <[EMAIL PROTECTED]> wrote:

> When setting up passwordless ssh on a cluster, its clear that the namenode
> needs to be able to ssh into task trackers to start/stop nodes and restart
> the cluster.
>
> What else is passwordless SSH used for?  Do TaskTrackers/DataNodes ever
> SSH into each other horizontally ? Or is SSH only used for one-way nn to tt
> operations?
>
> --
> Jay Vyas
> http://jayunit100.blogspot.com
>
> --
>
> Robert Dyer
> [EMAIL PROTECTED]
>

It isn't the NN that does the SSH technically, its the scripts we ship
for an easier start/stop:
http://wiki.apache.org/hadoop/FAQ#Does_Hadoop_require_SSH.3F

So wherever you launch the script, the SSH may happen from that point.

On Wed, Feb 6, 2013 at 4:36 AM, Jay Vyas <[EMAIL PROTECTED]> wrote:
> When setting up passwordless ssh on a cluster, its clear that the namenode
> needs to be able to ssh into task trackers to start/stop nodes and restart
> the cluster.
>
> What else is passwordless SSH used for?  Do TaskTrackers/DataNodes ever SSH
> into each other horizontally ? Or is SSH only used for one-way nn to tt
> operations?
>
> --
> Jay Vyas
> http://jayunit100.blogspot.com

--
Harsh J