My mum has a wee laptop that needs, when it boots up, to reverse-SSH connect itself to a server (so I can help out when needed).

I'm struggling to get the connection to persist when it is started by systemd.

In /reverse_SSH.sh I've got something like this:

#!/bin/bash
while true; do ssh -R 19123:localhost:22 mum@ sleep 1000
done

In /etc/systemd/system/reverse_SSH.service I've got something like this:

[Unit]
Description=reverse-SSH
[Service]
Type=fork
ExecStart=/reverse_SSH.sh
[Install]
WantedBy=multi-user.target

When I run sudo systemctl start reverse_SSH, the SSH connection does appear to happen, and the MOTD of the server can be seen in the output of sudo systemctl status reverse_SSH, but the SSH connection doesn't seem to persist and I can't access the machine on the server with a command like ssh sonnyboy@localhost -p 19123.

What nonsense am I doing wrong? Thanks!

0

1 Answer

I would prefer to use the autossh package for such service. So first install it:

sudo apt update && sudo apt install autossh

Then create configuration entry for your connection, by creating a new file within the directory /etc/ssh/ssh_config.d/. Let's call it reverse.ssh.. Here is an example:

sudo nano /etc/ssh/ssh_config.d/reverse.ssh.

# This file is loaded by /etc/ssh/ssh_config
Host reverse.ssh. HostName IdentityFile /root/.ssh/your_passles_id_rsa User mum Port 22 RemoteForward 19123 127.0.0.1:22 GatewayPorts yes Compression yes

• Note the SSH key is possession of the root user who will manage the connection by our service.
• The last two options are not mandatory.

Finally create the service:

sudo nano /etc/systemd/system/reverse-autossh-www-example-org.service

[Unit]
Description=Keeps a resident tunnel to open
#After=network.target
After=network-online.target
[Service]
User=root
ExecStart=/usr/bin/autossh -M 0 -N -q -o "ServerAliveInterval 60" -o "ServerAliveCountMax 3" reverse.ssh.
ExecStop=/usr/bin/killall -s KILL autossh
#ExecStop=/bin/kill $MAINPID
Restart=always
RestartSec=3
#Environment=AUTOSSH_GATETIME=0
[Install]
WantedBy=multi-user.target

Enable and start the service:

sudo systemctl daemon-reload
sudo systemctl enable reverse-autossh-www-example-org.service
sudo systemctl start reverse-autossh-www-example-org.service

I've used this configuration for last two years in order to solve similar task - it works like a charm. However, here are few references:

2

Your Answer

Sign up or log in

Sign up using Google Sign up using Facebook Sign up using Email and Password Submit

Post as a guest

Post Your Answer Discard

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy