[SOLVED] Get output from a shell script that does ssh two level

Issue

I have two shell scripts like below:

Script1:

ssh -q -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null my_username@jump_box <<EOF
ls
ssh -q -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null actual_host <<EOF1
sudo docker ps --format='{{json .}}'
EOF1
EOF

Script2:

details=nothing
ssh -q -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null my_username@jump_box <<EOF
ls
details=$(ssh -q -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null actual_host "sudo docker ps --format='{{json .}}'")
EOF
echo "${details}"

I need the docker details in a varilable in my local machine so that I can do some operations on it. The first script runs fine and I can see the output of the docker command on my local machine but the second script doesn't work. It seems to be hung/stuck and doesn't do anything and I have to forcefully quit it.

Solution

Like the comment from @Gordon Davisson, use a jumpbox.

But you can define it in the ~/.ssh/config file, too.

HOST my_jump_box
  hostname jump_box
  user my_username
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null 

HOST actual
  hostname actual_hostname
  user actual_user
  ProxyJump my_jump_box
  StrictHostKeyChecking no
  UserKnownHostsFile /dev/null 
  RemoteCommand sudo docker ps --format='{{json .}}'"

Then you can just use ssh actual

To fetch the output details=$(ssh actual).

Btw. Your specific problem could also be solved by changing script2 to:

#!/bin/bash
details=$(./script1)
echo "$details"

Answered By - jeb