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Accepted
Ashwin Nanjappa
Asked: 2013-04-10 07:48:27 +0800 CST

How to rsync between home computer and computer inside another network?

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All the computers I use run Ubuntu. To work from home, I SSH from my home computer to my lab computer as follows:

# First a port knock is needed
joe@homepc> telnet ssh.university.edu 9000

# Next SSH to one of the external SSH servers of university
# This logs me into one of many SSH servers serving as interface
joe@homepc> ssh [email protected]

# Finally SSH to my lab PC inside university network
student7@university999> ssh joedude@labpc

# And I am in my labpc
joedude@labpc>

How do I use rsync to sync a directory on labpc with a directory on my homepc? Also, it would be awesome if there is some way to automate all of this so that I can rsync with just a single command from my homepc.

ssh

1 Answers

  1. Best Answer

    There are several ways to solve this, however, because we want to run the rsync command on your home PC, I think the best way would be to create a tunnel from your home PC to the labpc, as follows:

    joe@homepc> ssh -L 2222:127.0.0.1:2222 [email protected]

student7@university999> ssh -L 2222:127.0.0.1:22 joedude@labpc

    Now, on your home PC, you should be able to ssh directly into the lab PC:

    joe@homepc> ssh -p 2222 joedude@localhost

    Once this is working, then you can build up an rsync script.

    I would add the following lines to ~/.ssh/config

    # Tunnel to labpc
Host labpc_tun
User joedude
Port 2222
# ProxyCommand  ... TODO: set up tunnel automatically
HostName 127.0.0.1

    Now, you should be able to do (in a separate window, after first two ssh logins are done):

    joe@homepc> rsync labpc_tun:/path-on-labpc/ /path-on-homepc/

    There are lots more improvements you could make after this, but I would wait until you get the first part working, and then see how much automation you need. To completely automate this you would need to use ssh-keygen to allow ssh logins without a password. You could also add more to .ssh/config for the first outgoing ssh leg. Using the ProxyCommand parameter in .ssh/config you could automate the entire thing.

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