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This is a guide for setting up a persistent reverse SSH tunnel using AutoSSH on Arch Linux.

Once completed, the service that will autostart at boot will open port 5000 on the remote SSH connection that will allow SSH connections back to the originating host.

Prepare the Environment¶

• Switch to the root user then switch to the:
  

  sudo -s
  

• Make sure the system is up to date:
  

  pacman -Syu
  

• Generate a root ssh keypair:
  

  ssh-keygen -t ed25519
  

• Copy the ssh public key to the remote host:
  

  ssh-copy-id bob@ssh.example.com
  

AutoSSH¶

• Install autossh:
  

  pacman -S autossh
  

Host Config¶

• Create a .ssh config file:
  

  nano ~/.ssh/config
  

  • And add the following:
    

    Host remote-tunnel-home
       HostName      ssh.example.com
       User          bob
       Port          7022
       IdentityFile  ~/.ssh/id_ed25519
       RemoteForward  5000 localhost:22
       ServerAliveInterval 30
       ServerAliveCountMax 3
    

Systemd Service¶

• Create the autossh reverse tunnel service file:
  

  nano /etc/systemd/system/autossh-reverse-tunnel-home.service
  

  • And add the following:
    

    [Unit]
    Description=AutoSSH tunnel to remote SSH host on local port 5000
    After=network.target
    
    [Service]
    Environment="AUTOSSH_GATETIME=0" 
    ExecStart=/usr/bin/autossh -M 0 -N remote-tunnel-home
    
    [Install]
    WantedBy=multi-user.target
    

• Refresh the systemd units:
  

  systemctl daemon-reload
  

• Start and enable the service at boot:
  

  systemctl start autossh-reverse-tunnel-home
  systemctl enable autossh-reverse-tunnel-home
  

Resources¶

• https://raymii.org/s/tutorials/Autossh_persistent_tunnels.html
• https://www.everythingcli.org/ssh-tunnelling-for-fun-and-profit-autossh/
• https://blog.sleeplessbeastie.eu/2014/12/23/how-to-create-persistent-reverse-ssh-tunnel/
• https://wiki.archlinux.org/index.php/Secure_Shell#Run_autossh_automatically_at_boot_via_systemd