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At work, we have a number of servers that we can only SSH into from our jumpbox server.

Every now and then I need to execute a command on these servers. For example, if I want to execute df -H on server-1, I run this command:

ssh jumper@jumpbox 'ssh admin@server-1 ''dh -H'''

Our jumpbox has the keys to SSH into server-1, and my local workstation has the keys for SSHing into the jumpbox.

In order to simplify this, I have written a script called jumpbox.sh that looks like this:

#!/usr/bin/env bash
ssh jumper@jumpbox @

Then I can simply run

jumpbox.sh ssh admin@server-1 dh -H

To achieve the same goal. Is there a way I can achieve this by configuring my environment (e.g. by editing ~/.ssh/config), rather than using this custom script?

I have found a few articles as well as some questions on StackOverflow that discuss how using ProxyCommand we can achieve this, but I can't seem to make it work.

First of all, the manual say this about ProxyCommand:

Specifies the command to use to connect to the server. The command string extends to the end of the line, and is executed with the user's shell.

If I am not wrong, this means that if I have the following configuration:

Host server-1
    ProxyCommand  ssh jumper@jumpbox nc %h %p

And then on my shell I execute

ssh server-1 dh -H

Then dh -H will be ignored. So looks like ProxyCommand is helpful in opening a new interactive SSH session, but not running one off commands. Is this correct?

Also I don't quite understand what is nc's role here?

To summarize, my question is:

Is there a way to configure my environment using ~/.ssh/config, etc. so that when I run ssh admin@server-1 dh -H, for example, the command is run through the jumpbox server?

Community
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Behrang Saeedzadeh
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1 Answers1

0

Yes... You can achieve by ProxyCommand. From your Work Station, try to run "ssh admin@server-1 dh -H".. it will be executed by exec ssh -q nc server-1 22... So Proxycommnad helps to connect the client server, once connected, the client shell will execute the command that your've given from your workstation.

so .. your ~/.ssh/config should have the below entry

Host server* ProxyCommand ssh -q jumper@jumpbox nc %h %p StrictHostKeyChecking=no

Chennai_Linux
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