why is emacs allowing multiple instances?

Question

Around the time I fresh installed Ubuntu 12.04, I noticed that I can start multiple instances of Emacs. I find this annoying because I will think that a buffer should be open, but I'm in the wrong Emacs window. I may have changed something in .emacs, but I really don't think I did. I also reverted all of my customizations that are stored in ~/.emacs.d/custom.el. Emacs previously would give some error about another emacs server being open when I would attempt to start an additional instance of it, but it no longer does this. Any ideas on how to restore this behavior?

Answer 1

You are always allowed to start another instance. If you don't want to start another instance, then run emacsclient instead of emacs and the file will be opened in the current instance instead.

Answer 2

Previously, I would get the following error:

Warning (server): Unable to start the Emacs server.
There is an existing Emacs server, named "server".
To start the server in this Emacs process, stop the existing
server or call `M-x server-force-delete' to forcibly disconnect it.

Since I started having problem described in this question, this error message had not been coming up. I managed to get it back though, and I did it by putting (server-start) in my ~/.emacs.