I am using tmux and I'm observing a strange behaviour. It happens from time to time that when I press "n" on my keyboard, the focus switching to tmux control and the message "Not in a mode" is displayed.

I supposed at some point I triggered something for that to happen.

It happens only in one session in one pane (number 5). Even if I close that pane, the "new pane 5" will adopt that behaviour. And if I kill all but 4 panes the behaviour is gone but returns as soon as I have 5 panes.

This is probably some setup mixup.

How can I find debug information to further investigate this?

  • I have started to observe this as well. What version are you using? I have started to observe this when I upgraded to 2.5
    – Patryk
    Aug 31, 2017 at 14:41
  • I use 2.5 as well
    – leifg
    Aug 31, 2017 at 19:06
  • 6
    I believe this is relevant to our case ( I tested the provided fork and it works for me) github.com/tmux-plugins/tmux-copycat/issues/109. I believe you can close this question and comment in that issue.
    – Patryk
    Sep 1, 2017 at 8:09

1 Answer 1


From the man page:


Request verbose logging. Log messages will be saved into tmux-client-PID.log and tmux-server-PID.log files in the current
directory, where PID is the PID of the server or client process. If -v is specified twice, an additional tmux-out-PID.log file is generated with a copy of everything tmux writes to the terminal.

The SIGUSR2 signal may be sent to the tmux server process to toggle logging between on (as if -v was given) and off.

pkill -SIGUSR2 tmux should toggle it in running processes, like a tmux server.

I have tmux 3.2a installed, and don't have the tmux-copycat plugin installed. I have debugged some issues with tmux using these logs, but can't find that history in my laptop's local shell history—going back two years.

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