Fwd: User bus conclusion

David Faure faure at kde.org
Tue Nov 9 23:46:08 GMT 2010

On Wednesday 10 November 2010, Thiago Macieira wrote:
> So I have to ask again: do we allow or support multiple logins of the same
> user, on the same machine (same $HOME)?

Yes we do, that's exactly why the kdeinit socket is called kdeinit4__$DISPLAY.

Typical use case for me:
I'm logged in on my desktop machine, and then I use ssh -X from my laptop
(-> new $DISPLAY) and I start KDE apps from there. They start their own 
kdeinit4 + klauncher + kded4, and work fine. And indeed wallet password dialogs 
show up on that display, as expected.

> However, on second thought, I came to the conclusion that running two 
> instances of kwalletd would be a problem of itself: the two wallets trying 
> to have write access at the same time could end up stepping over each
> other's toes, causing data loss (one of the instance's changes or, worse,
> all of the data).

Now that's a good point, though. In theory this could mess up.
Although with the case of kwallet itself it's rather unlikely, since the user 
would have to click "store this password" at almost the same time on two 

But yeah, using kmail from two logins at the same time would be a very bad 
idea -- so it actually uses a lock file to prevent that.

So, why not let apps use locking (note that KConfig already uses a lock file 
internally), and let us log in from multiple displays? I don't understand the 
wish to lose features in this area. The old mess with "export DISPLAY=:0 
doesn't give me the existing session bus" is actually fixed nowadays, the 
session bus is found automatically, so why not leave things as they are?

David Faure, faure at kde.org, http://www.davidfaure.fr
Sponsored by Nokia to work on KDE, incl. Konqueror (http://www.konqueror.org).

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