SFTP through proxy

Question

I have a large amount of data on scratch space at computer b that I want to get.

In my network I cannot directly connect to computer b (ssh exits with "No route to host"); I must first connect to computer a, and then connect to computer b.

I cannot move the data from the scratch space on computer b to computer a because of a disk quota that is imposed on me at computer a.

How can I move the data from computer b to my computer in this situation?

Answer 1

If nc suggested by Ignacio is not available on computerA, you can create a tunnel:

ssh -f -N -L 1234:computerB:22 computerA

(drop -f to keep it from going to the background). You should then be able to connect to port 1234 on localhost to access computerB, i.e.

scp -P 1234 user_on_computerB@localhost:/awesome/stuff/there /here

Answer 2

Use ProxyCommand in your ssh config, along with nc on computer A:

Host computerB
    ProxyCommand ssh computerA nc computerB 22

Answer 3

• one option is to mount b into a, from a:

  sshfs computer_b /mnt/PC_b
  

then copy directly to the mount

• another option if a and b machines are in the same LAN, to export via NFS data folder from b machine and mount it in a machine