autossh

TLDR

Create persistent SSH tunnel

$ autossh -M [20000] -N -L [8080:localhost:80] [user@remote]

Tunnel with no monitoring port

$ autossh -M 0 -N -L [8080:localhost:80] [user@remote]

Reverse tunnel

$ autossh -M [20000] -N -R [8080:localhost:80] [user@remote]

Run in background

$ autossh -f -M [20000] -N -L [8080:localhost:80] [user@remote]

SYNOPSIS

autossh -M monitorport [sshoptions] destination

autossh wraps SSH connections with automatic reconnection. It monitors the connection and restarts it if it dies, making SSH tunnels and connections persistent.
The tool is essential for maintaining long-running SSH tunnels, remote port forwards, and SOCKS proxies.

PARAMETERS

-M port[:port]

Monitoring port(s). Use -M 0 to disable port monitoring

-f

Background after authentication

-N

No command execution (forwarding only)

-L port:host:port

Local port forward

-R port:host:port

Remote port forward

-D port

SOCKS proxy

All other ssh options are supported.

ENVIRONMENT VARIABLES

AUTOSSH_GATETIME

Seconds before first connection check (default: 30)

AUTOSSH_POLL

Poll time in seconds (when monitoring disabled)

AUTOSSH_DEBUG

Enable debug logging

CAVEATS

Monitoring ports must be free on both sides. ServerAliveInterval in SSH config can replace monitoring. May not detect all disconnection types. Recent SSH versions have built-in keepalives.

HISTORY

autossh was created by Carson Harding to address the problem of SSH connections dying without notification, first released around 2002.