Sometimes, in order to improve security and restrict access, System Administrators can set up one intermediate machine (“jump”) that should be used to access any secure machine. So to access this secure machine we have to do ssh to jump machine (or intermediate machine) and then from that machine we have to do ssh to another machine. Although its good in terms of security but it adds one more step in developers work-flow. Furthermore, it complicates scp too. As now you have to download or upload to jump server first then you can do the same operation from jump to secure machine.
Here are the steps that can help in reducing this complication. After following these instructions, the intermediate or jump machine step will become completely transparent to you.
To make it easier to understand. Let’s say jump is the hostname of the machine which is the intermediate one and prod1 is the target machine.
So with that intermediate step these will be the commands that you have to run:
your-machine$ ssh jump
jump$ ssh prod1
And for scp:
jump$ scp prod1:~/somefile.txt .
your-machine$ scp jump:~/somefile.txt .
To make it simple, we need to edit ~/.ssh/config file. Create it if it doesn’t exist
Now just add these entries in ~/.ssh/config file
User <user name>
Hostname <ip of jump machine>
Hostname <ip of prod 1>
ProxyCommand ssh -o 'ForwardAgent yes' jump 'ssh-add && nc %h %p'
Now we can run this command. No more jump step needed.
your-machine$ ssh prod1
And it helps with scp too.
your-machine$ scp prod1:~/somefile.txt .
And the file will be downloaded on your machine without you ever worrying about jump server.