Definition: '.tmux_utf8.conf' is a file containing command-line arguments used by tmux, a terminal emulator with a lightweight CLI for managing terminals in Unix-based operating systems like Ubuntu. Definition: This file contains arguments that are passed to tmux when it starts up, typically specifying the color scheme of terminal output. It can be found in various places on your system, such as `/etc/tmux.conf`. The most commonly used command-line argument is `-v` for verbose mode, which causes tmux to display more details about its commands and arguments when they're run interactively (e.g., `tmux new-session`).