Reverse tunnel local ssh to remote server on ubuntu and maintain it alive with systemd and autossh

reverse_tunnel.sh

# On the remote machine create a user with no bash
sudo useradd -m -s /bin/false ssh_forwarder
# Take control of the user with bash
sudo -Hu ssh_forwarder /bin/bash
cd ~
mkdir .ssh
ssh-keygen
chmod 700 .ssh/
mv .ssh/id_rsa.pub .ssh/authorized_keys
chmod 600 .ssh/authorized_keys
chmod 600 .ssh/id_rsa

# copy the .ssh/id_rsa file to the local machine in /root/.ssh/ssh_forwarder_key
# create a /root/.ssh/config file with the tunnel content

Host iwant
  HostName 82.83.126.95
  User ubuntu
  RemoteForward 8022 localhost:22
  Compression yes
  ExitOnForwardFailure yes
  ServerAliveInterval 30
  ServerAliveCountMax 3

# this will forward the local ssh to the remote port 8022
# test on the local machine
ssh iwant_tunnel (This should connect and return because of /bin/false)
ssh -N iwant_tunnel should block
# while the ssh -N is still running try on the remote machine
telnet 127.0.0.1 8022 (This should show openssh protocol)

# install autossh (a prog that keeps alive ssh tunnels and restart them when they die)
sudo apt-get install autossh

# install a systemD service on the local machine for this autossh
# vim /etc/systemd/system/autossh-iwant-tunnel.service
[Unit]
Description=AutoSSH reverse tunnel service to iwant 22 to 8022 remote
After=network.target

[Service]
Environment="AUTOSSH_GATETIME=0"
ExecStart=/usr/bin/autossh -M 0 -N iwant

[Install]
WantedBy=multi-user.target

systemctl daemon-reload
systemctl start autossh-iwant-tunnel
systemctl status autossh-iwant-tunnel
● autossh-iwant-tunnel.service - AutoSSH reverse tunnel service to iwant 22 to 8022 remote
   Loaded: loaded (/etc/systemd/system/autossh-moneyfit-tunnel.service; disabled; vendor preset: enabled)
   Active: active (running) since Wed 2017-01-18 23:34:10 UTC; 13s ago

# you can add more tunnels in the /root/.ssh/config file by adding multiple RemoteForward
# restart the tunnel by doing 
systemctl restart autossh-iwant-tunnel