This is an old revision of the document!

03. [??p] Reverse SSH

TODO

In the following commands [localhost] means that the command should be executed on your computer, [gcloud] on the Google Cloud VM, and [fep] on fep.grid.pub.ro.

# create the .ssh directory (if not already there)
[gcloud]$ mkdir -p ~/.ssh
 
# print out your fep.grid.pub.ro public key and copy it
[fep]$ cat ~/.ssh/id_rsa.pub
 
# configure your fep.grid.pub.ro public key on gcloud instance
[gcloud]$ vim ~/.ssh/authorized_keys

# create a reverse ssh tunnel from your computer to the cloud instance
[localhost]$ ssh -T -N -R 43210:localhost:22 ${GCLOUD_USERNAME}@${GCLOUD_IP}
 
# show tcp listeners (bound ports, processes, etc.)
[gcloud]$ sudo netstat -tlpn
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 127.0.0.1:43210         0.0.0.0:*               LISTEN      1931/sshd: ........ 
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      448/systemd-resolve 
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      893/sshd: /usr/sbin
 
# test that the reverse ssh tunnel works
[gcloud]$ ssh ${LOCALHOST_USERNAME}@localhost -p 43210
 
# connect from fep.grid.pub.ro to your localhost via gcloud instance
[fep]$ ssh -J ${GCLOUD_USERNAME}@${GCLOUD_IP} ${LOCALHOST_USERNAME}@localhost -p 43210