Ctrl-C does not work in tmux window

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http://unix.stackexchange.com – I have a Mini2440 ARM Board, and I have put a base Debian 6.0 system on it using multistrap. I have used tmux to run several processes in defferent windows from /etc/rc.local. I connect to the board using its serial port and an inittab entry to run getty on that port. I use picocom as serial communicator. when root logs in, ~/.bashrc attaches him to the already running tmux server, and processes can be easily monitored. the actual command is exec tmux attach-session -t "main". tmux runs with default config. everything works, except one of the processes (a shell script around pppd) does not (HowTos)