Ubuntu – Execute a command on local computer from a connected remote SSH host

remote accessssh

Say I have connected to a remote computer via SSH. From a program on this remote computer, I need to execute a command on my local computer (the connection initiator).

Which raises the question: is it possible to leech onto the existing connection between the two computers to run a command on the local computer?

I have considered running the command ssh user@host-of-connecting-party <command> on the remote computer to establish a reversed connection. But this is harder to automate and will require user intervention. I was hoping I could fully automate it, or at least detect the user/hostname of the connected user.

Best Answer

@62mkv's answer is a much better solution. Use that.

For completeness and curiosity though, if you have an ssh server running on your local machine, you could create an ssh tunnel to allow ssh connections from the remote host on port 20202 back to the local one on port 22. Example command:

ssh -R20202:localhost:22 remoteuser@remotehost.com

This will start an ssh connection, but also set up a tunnel back to the ssh server running on your machine. Then you can do this, when ssh'ed into the remote host:

ssh -p 20202 localuser@localhost

Of course, this can quickly get confusing - especially if the technique is nested more than once. It adds a bit of latency, too - since everything you execute on your local machine is bounced through the remote host.

Additional information about ssh tunneling for those whose curiosity hasn't been satisfied yet can be found in answer to this unix stackexchange question.

Related Solutions

Ubuntu – Share first ssh connection to user@host opportunisitically using ControlMaster

From the ssh_config man page:

ControlMaster
    ...
    Two additional options allow for opportunistic multiplexing: try
    to use a master connection but fall back to creating a new one if
    one does not already exist.  These options are: “auto” and
    “autoask”.  The latter requires confirmation like the “ask”
    option.

So if you configure ssh with ControlMaster auto, it will attempt to connect to use an existing SSH session, falling back to creating a new master connection if that fails.

So a configuration like the following is probably what you're after:

ControlMaster auto
ControlPath ~/.ssh/control/%r@%h:%p

Ubuntu – Cannot establish ssh connection to computer on local network

Make sure you install the openssh server in the main PC (where you are trying to ssh into)

sudo apt-get install openssh-server

then check if the Ubuntu firewall is turne on?

sudo ufw status

if yes or no still issue the following command

sudo ufw allow ssh and sudo ufw reload

Now try to ssh using

ssh user@ip-address-of-the-machine

If this doesn't work try to add the INPUT and OUTPUT firewall rule in IPTABLE

sudo iptables -I INPUT -p tcp --dport 22 -j ACCEPT

sudo iptables -I OUTPUT -p tcp --dport 22 -j ACCEPT

sudo iptables-save

sudo service iptables restart

You might have to restart the network manager as well. Good Luck!

Best Answer

Related Solutions

Ubuntu – Share first ssh connection to user@host opportunisitically using ControlMaster

Ubuntu – Cannot establish ssh connection to computer on local network

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