Simple ssh tunnel script

When replicating CouchDB you need either VPN oder authentication or simply a SSH tunnel. No big deal normally a simple ssh -L... does the trick but I ended up with those SSH sessions that blocked ports and hung around and it was not the way to go in terms of automating rollouts where you need that port once and then never again.

A bit of googling brought up a script of the bacula guys that had the same problem and I adopted their script a bit to fit my needs. Here is what I came up with:

{{< highlight sh >}} #!/bin/sh

Establishes a self-killing SSH tunnel to the

given SSH server, and forwards the correct

ports for couchdb usage.

USER=[YOUR USER HERE] HOME=$(grep "^$USER:" /etc/passwd | cut -d : -f 6) CLIENT=$1 SSH=/usr/bin/ssh DESTPORT=5985

echo "Starting SSH-tunnel to $CLIENT..."

-f means: go into background

-C means: use compression

-2 means: only use SSH2

-L 5985:localhost:5984 means: when forward 5985 to destination:5984

sleep 60 is a simple command that will execute on the server and does

nothing for 60 seconds,

then it exits. This keeps ssh running for 60 seconds. Once we connect

to the FD, that

connection will keep ssh running even beyond the 60 seconds.

Using this approach, we do not need to tear down the tunnel later, it

disconnects itself

automagically.

${SSH} -fC2 -L ${DESTPORT}:localhost:5984 ${CLIENT} sleep 60 >/dev/null 2>/dev/null

give ssh a little time to establish the connection.

sleep 10 {{< / highlight >}}

Put it in a file called sshtunnel and make it executable. Usage is as simple as ./sshtunnel user@host or without the user if it is the same you are using in the $USER variable.