In Breezy I used to run several apps as another user on the same machine via 'gksu -u <other-username> <cmd>'
(after giving the other user's password to gnome-keyring when prompted). Now I've upgraded to Dapper this fails. No prompt for password, just the errors:-

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

unable to display ":0.0"

It works if I just do 'gksu <cmd>' to run the cmd as root, but not with '-u <username>' to run the cmd as a different user.

If I do: 'xhost +local:' first (as my main user and sudoer), then I can use 'gksu -u' without any problems. But I need to accomplish this from launchers without having to enter the xhost command first.

I've tried creating /etc/X0.hosts (with a zero) and adding the line: 'local:', then restarting X. This seems to do part of the job. If I then do 'xhost' it shows 'LOCAL:' as needed,
BUT if I do 'gksu -u <otheruser> <cmd>',
or 'sudo -u <otheruser> xhost', I just get the Xlib errors.
I've also tried lots of other possibilities in X0.hosts eg: 'localhost', '<username>', '+local:', etc, etc.

In a terminal I can do:-
'xhost +local:; gksu -u <otheruser> nautilus' on one line, but this won't work from the launcher - it doesn't seem to like the special characters ';' or '&&'.

The only way I can find to do 'xhost +local:' automatically is to put the xhost cmd and the gksu-app cmd into a separate script eg:
then to call the scripts from the launchers.

Since I have several apps to be launched on several different machines, this seems overly complicated and laborious. I don't really want to allow other users to connect from the network via TCP, just other users on the same machine.

Surely there must be a more elegant way to do this!? - eg: via /etc/X0.hosts or similar?

The way I do it is, I have the line "xhost +LOCAL: >/dev/null" in my ~/.bashrc file.

Binary, thanks for your reply - I had mixed results (which I think you hinted at), but it prompted me to find a better way - for me at least. I'm using Gnome by the way.

After putting the xhost cmd into .bashrc as you suggested I found:-
When I do a normal fresh login to a blank desktop, my gksu launchers don't work.
If I restart X via Ctrl-Alt-Bkspc, the desktop opens with Nautilus and Gnome Terminal displayed (I don't know why, but it does this every time) - and in this case the launchers work first time - and no passwords needed!
If I login normally, and then open the terminal but do nothing in the terminal - then the launchers work, again without requesting a password.

I have now put the cmd 'xhost +local:' into Gnome > System > Prefs > Session > Startup Programs, and the launchers now work reliably. Gksu password behaviour seems normal. I guess its something to do with the X session being fully initialized when the xhost cmd is executed.

Haz