/usr/bin/byobu-select-backend is in byobu 5.87-1.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63  | #!/bin/sh -e
#
#    byobu-select-backend
#    Copyright (C) 2011-2014 Dustin Kirkland
#
#    Authors: Dustin Kirkland <kirkland@byobu.co>
#
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, version 3 of the License.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
PKG="byobu"
[ -r "$HOME/.byoburc" ] && . "$HOME/.byoburc"
[ -z "${BYOBU_PREFIX}" ] && export BYOBU_PREFIX="/usr" || export BYOBU_PREFIX
. "${BYOBU_PREFIX}/lib/${PKG}/include/common"
usage () {
	cat <<EOT
Usage: $0 [screen|tmux]
    Without any parameters, it runs interactively.
EOT
	exit 1
}
prompt() {
	local choice
	echo
	echo "Select the byobu backend:"
	echo "  1. tmux"
	echo "  2. screen"
	echo
	printf "Choose 1-2 [1]: "
	choice=$(head -n1)
	case $choice in
		1|"") _RET="tmux" ;;
		2) _RET="screen" ;;
		*) prompt ;;
	esac
}
case $1 in
	"")
		prompt
		choice="$_RET"
	;;
	screen|tmux)
		choice="$1"
	;;
	*)
		usage
	;;
esac
echo "BYOBU_BACKEND=$choice" > "$BYOBU_CONFIG_DIR/backend"
 |