With an empty .bashrc and .tmux.conf file, when I execute:
My screen brightness gets reset to the default (on a Dell XPS running Ubuntu 14.04.1). Tmux version's is 1.8.
Interestingly, this also happens when I create a new pane, suggesting it's related to the execution of a new shell.
However, it does not happen when opening a new gnome-terminal.
How can I find out which shell tmux executes? It seems to be different enough from gnome-terminal's one that it can execute this brightness reset command.