How to ssh with a node from another node with out password

[Gandhimathi Velusamy]

Hi,

I want to ssh to another node from a node with out giving password. I need to run some script from remote without giving password by ssh into it. When I was working on Hadoop on GENI, I have created a different user and I could ssh with that user on a remote node without password by generating key pair and copying the public key into remote node. But now I don't want to create a separate user, I would like to use my geni username on the node and want to ssh from other node to execute the script. Could you please help me how to  do that.

I tried as below:

1. ssh-keygen -t rsa -P "" (generated rsa key pair with empty password)

2.cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys ( public key is added into authorized key to allow ssh into the local host)

3.ssh-copy-id -i $HOME/.ssh/id_rsa.pub gvelus01@linc1 ( To copy the public key to the remote node in this case linc1)

I was able to do till the second step and couldn't do the 3rd step. 

When I tried to copy the public key to the remote node it is asking password for the user on the node, if I give the pass phrase of mine, it is  giving me error as permission denied. try again.

My doubt id is it possible to ssh from other node to a node without giving password for the geni username on that node as explained above.

Thanks.

Gandhimathi Velusamy

Graduate Research Assistant

College of Technology

University of Houston

gvel...@uh.edu

[Sarah Edwards]

Hi,

The simplest way to solve this problem is to use an ssh agent and enable agent forwarding using the -A option to ssh.

Here's the rough idea assuming your local machine is some sort of *nix:

# use an ssh agent to offer your private key to ssh connections

local> ssh-add /path/to/my/privatekey

# login into your first node in the usual way, but provide the -A option in addition to what you usually do (eg provide username, hostname and port information in the usual way)

local> ssh -A firstnode.example.com 

# now login to a second node from the first node.  The -A option given to the first node will allow you to log into the second node.

firstnode> ssh secondnode.example.com

secondnode>... your command here...

Let me know if that doesn't work.

Cheers,

Sarah

PS In order to manually append your public key to your authorized_keys file, you could should just be able to scp id_rsa.pub from your local machine to linc1, then ssh to linc1 from your local machine, and finally repeat step 2 on linc1.

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*******************************************************************************

Sarah Edwards

GENI Project Office

BBN Technologies

Cambridge, MA

phone:    (617) 873-2329

email:    sedw...@bbn.com

[Gandhimathi Velusamy]

Hi Sara,

     Yes. I am able to do as you told first by adding ssh-add the path of id_geni_ssh_rsa from a VM on my laptop and first login with h1 and then from h1 to linc1. It worked with the host names like pc4.geni.kettering.edu.

Thank you very much. But how could I do the same from putty. I feel comfortable using putty to connect with several nodes simultaneously from windows OS as I need to run several application on several nodes.

Thanks

Gandhimathi

[Niky Riga]

Hi Gandhimathi,

The capability that Sarah described is called ssh agent forwarding. A quick google
search for putty and this capability turned up this page:

http://www.howtogeek.com/125364/how-to-ssh-hop-with-key-forwarding-from-windows/
Look at the session: Enable SSH Agent forwarding (PuTTY/mRemote)

I hope this is helpful,
Niky

Gandhimathi Velusamy

May 29, 2014 at 1:02 PM

Hi Sara,

     Yes. I am able to do as you told first by adding ssh-add the path of id_geni_ssh_rsa from a VM on my laptop and first login with h1 and then from h1 to linc1. It worked with the host names like pc4.geni.kettering.edu.

Thank you very much. But how could I do the same from putty. I feel comfortable using putty to connect with several nodes simultaneously from windows OS as I need to run several application on several nodes.

Thanks

Gandhimathi

On Thursday, May 29, 2014 12:50:40 AM UTC-5, Gandhimathi Velusamy wrote:

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Gandhimathi Velusamy

May 29, 2014 at 1:50 AM

Hi,

I want to ssh to another node from a node with out giving password. I need to run some script from remote without giving password by ssh into it. When I was working on Hadoop on GENI, I have created a different user and I could ssh with that user on a remote node without password by generating key pair and copying the public key into remote node. But now I don't want to create a separate user, I would like to use my geni username on the node and want to ssh from other node to execute the script. Could you please help me how to  do that.

I tried as below:

1. ssh-keygen -t rsa -P "" (generated rsa key pair with empty password)

2.cat $HOME/.ssh/id_rsa.pub >> $HOME/.ssh/authorized_keys ( public key is added into authorized key to allow ssh into the local host)

3.ssh-copy-id -i $HOME/.ssh/id_rsa.pub gvelus01@linc1 ( To copy the public key to the remote node in this case linc1)

I was able to do till the second step and couldn't do the 3rd step. 

When I tried to copy the public key to the remote node it is asking password for the user on the node, if I give the pass phrase of mine, it is  giving me error as permission denied. try again.

My doubt id is it possible to ssh from other node to a node without giving password for the geni username on that node as explained above.

Thanks.

Gandhimathi Velusamy

Graduate Research Assistant

College of Technology

University of Houston

gvel...@uh.edu

[Gandhimathi Velusamy]

Hi Niky,

Yes. With in putty I checked the option of allow agent forwarding and now I am able to ssh linc1 from h1. 

Thank you so much!

Thanks

Gandhimathi