This is my method to keep connected with a remote Raspberry Pi that has a static external IP address and lives behind a NAT, where I don’t have control over the router (so no port forwarding). For your use case, you might want to choose another method (there are plenty on the world wide web, I’m sure you can find them), but the simple method below works for me.
Create a new user with
user tunnel pass SomeComplicatedPass
You need a modification to
sshd_config. At the end of the file, add a Match block to prevent password-based logins (only allow keybased logins for user tunnel) so the password above is of little use to the outside world 😉
# Match blocks must be at the and of this config file, see: # http://unix.stackexchange.com/questions/67334/openssh-how-to-end-a-match-block Match User tunnel PasswordAuthentication no
Login to Hunter. I assume evert as your username on Hunter 🙂
Create the reverse tunnel using:
ssh -N -R 2222:localhost:22 tunnel@Base
Or, more sophisticated:
autossh -M 0 -q -f -N \ -o UserKnownHostsFile=/dev/null \ -o StrictHostKeyChecking=no \ -o "ServerAliveInterval 60" \ -o "ServerAliveCountMax 3" \ -R 2222:localhost:22 \ tunnel@Base
This can be done best by doing it from cron and with a script.
crontab -e @reboot /home/evert/tunnel.sh 60
My script has a few more tricks (updated 2017-12) and is named
You can download my files: reverse_ssh_tunnel.zip
First login to Base, then connect to Hunter using:
ssh evert@Base ssh localhost -p 2222
And from there, you can play with Hunter.