Localhost as ssh bridge between two server

Question

I can connect via ssh to two hosts, say host1 and host2 and I need to copy files from host1 to host2 via rsync.

I know I can realize this first copying files from host1 to localhost and then from localhost to host2 or perform simple copy via scp -3 <user1@host1:/file_path1> <user2@host2:/file_path2>, but my goal is test ssh tunnel via rsync.

Someone can help me?

Extra:

I've read about ssh tunnel, but can't reach my goal... probably there's something I've don't understood. For example if I run

$ ssh -L 9999:host2:22 user_host1@host1

this means: map my local port 9999 to port 22 of host2 and connect to host1 as user user_host1 but... with this mapping what's the purpose of connect to host1 ?

Answer 1

First of all, thanks to mmv-ru: your answer was a great start-point to find what was wrong in my case.

I've write an answer to explain step by step what to do:

1 Remote Loopback

in one console run ssh -R 127.0.0.1:9999:host2:22 user_host1@host1 -N

2 Work on remote

in other console goto server host1 ssh user_host1@host1 and then run

rsync -e "ssh -p 9999" /file_path1 [email protected]:/file_path2

in my case this command fails, because I need:

1 - add [127.0.0.1]:9999 to my known hosts by clicking yes

2 - since I ssh to host2 via a single key, I need to add that key into host1 and set it' permissions to 400.

So my command is

rsync -e "ssh -p 9999 -i my_ssh_key_for_host2" /file_path1 [email protected]:/file_path2

and works!!!

3 ALL IN ONE

after step 2 (creation key for host2 on remote host1) I can perform all with one command:

ssh -R 127.0.0.1:9999:host2:22 user_host1@host1 'rsync -e "ssh -p 9999 -i my_ssh_key_for_host2" /file_path1 [email protected]:/file_path2'

Note single quote in second part!

Regards,

Sim

Answer 2

• Assume You unable to connect ssh directly from host1 to host2. (Otherwise simplest is direct connect host1 to host2)
• Assume it impossible to connect from host1 or host2 to Your PC.

Next Command make rsync

ssh -R 127.0.0.1:9999:host2:22 user_host1@host1   rsync -e "ssh -p 9999" /file_path1 [email protected]:/file_path2

Lets parse it:

• ssh make connection to host1
• -R 127.0.0.1:9999:host2:22 listen on remote (host1) loopback at port 9999 and forward connection over client host to host2:22
• on host1 rsync run
• -e "ssh -p 9999" force using non default ssh port for connection
• rsync local path /file_path1 to remote path [email protected]:/file_path2 we make connection to user2@host2 but as address we use mapped earlier loopback port

I hope not mistyped in command.

UPD

For troubleshooting try at first connect interactive ssh with tunnel

$ ssh -R 127.0.0.1:9999:host2:22 user_host1@host1

and manual ssh connect over tunel

[user_host1@host1 ]$ ssh -p 9999 [email protected]

Tunneling can be disabled in sshd config at host1.