processes remain after "ssh -X <user>@localhost firefox -no-remote"

This isn't really a solution, but try the following for diagnostic purposes(see paragraph below steps for a description of what I think is happening):

1) Create a file in the user's home directory with the following (I pulled part of this from the dbus-launch man page):

#!/bin/bash
if test -z "$DBUS_SESSION_BUS_ADDRESS" ; then
             eval ‘dbus-launch --sh-syntax --exit-with-session‘
fi
/usr/bin/firefox -no-remote

2) Make this file executable (chmod +x filename.sh)
3) Now instead of the link you set up, ssh into the machine as the user but do the following:

ssh -X mor@localhost ./filename.sh

Basically, sshd is sticking around because the two processes are running, if we can get rid of those two processes, sshd dies. I think what is happening is that firefox is autostarting the dbus-daemon (hence the dbus-launch process). since dbus-daemon is a child process of dbus-launch, dbus-launch isn't going away until dbus-daemon goes away, and dbus-daemon isn't going to go away because dbus-launch wasn't called with --exit-with-session. This is just the theory I came up with after reading the dbus-launch man page, so it could be entirely off base. What the directions above hope to do is preemptively start dbus-launch with the --exit-with-session parameter, thus, when you close firefox and end your session, dbus will actually exit. That is, if that script does what I think it should do. :-)

If you have the time to try this out, please post back with any results.

Dear Steven,

Look:
dawn@dawn-desktop:~$ ssh -X mor@localhost '~/.firefox-remote'
DBUS_SESSION_BUS_ADDRESS='unix:abstract=/tmp/dbus-icAoNFOkEg,guid=e194c236d93dee4c9b5df5474a44d0f8';
export DBUS_SESSION_BUS_ADDRESS;
DBUS_SESSION_BUS_PID=30413;
DBUS_SESSION_BUS_WINDOWID=142606337;

firefox starts and I close it and dbus still runs. I press <Ctrl>+C to stop it and then 'exit' to close the ssh session.

Many blessings.

OK. So I guess my script didn't work right. What happens if you do the following:

ssh -X mor@localhost dbus-launch --exit-with-session --binary-syntax firefox -no-remote

or

ssh -X more@localhost dbus-launch --binary-syntax firefox -no-remote

If we don't end up figuring out a solution to this, I suppose it would
always be possible to write a script that kills dbus after firefox
returns and then simply have your link run that script--but that hardly
seems optimal.

You may want to respond to this simply so that your question gets put
back into an open state, making it more likely that somebody will see
it.

> ssh -X mor@localhost dbus-launch --exit-with-session --binary-syntax firefox -no-remote
does the same. I have to <Ctrl>+C it.

> ssh -X more@localhost dbus-launch --binary-syntax firefox -no-remote
with this, after I close firefox, I get a prompt but dbus is running in the bg.

I've linked this to LP#392543 .