Updating a post I saw from 2014...this problem still exists.
The error message is, "Geany tried to access the Unix Domain socket of another instance running as another user...."
The sign is that geany will not start and gives a dialog with this error message.
I saw a post here from 2014 that claimed the problem was solved and posted a 'solution'. It did not really adequately describe the problem nor why suggested solution works. It was a good stepping off place to find the problem though. Note the dialog for geany has not been updated to be any more meaningful (the quote above does not describe the problem to mere users.) It appears that geany was stopped without cleaning up all of its open 'sockets' and one must exist in a current configuration directory. Removing the directory will clear the problem but any settings or history may also be lost. A better solution is to find the socket and delete it (rm [socket name]) If you look in your ~/.configs/geany directory, you will see a listing with a similar name to:
geany_socket_I3770K__0 -> /tmp/geany_socket.b9fcdd9b
Delete this and you should be back directly to your previous (normal) state of operation. Someone did mention using gksu or gksudo instead of sudo, probably mysterious but good advice to users. A terminal construct such as (exactly):
(gksu geany &)
will start it up nicely. Just enter password when prompted.
I believe my post has new information that updates or is more relevant than the post from 2 years ago.
/..
Update: Geany tried to access the Unix Domain socket of another instance running as a
