systemd/user/backdoor@.service

   1 [Unit]
   2 Description=Reverse SSH Tunnel Service
   3 After=network.target
   4
   5 [Service]
   6 ExecStart=/usr/bin/ssh -i ~/.ssh/id_ed25519_port-forward -NT -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -R 22222:localhost:22 %i