Description of problem: The terminal multiplexer tmux is compiled without utempter. The configuration changed in 2.4 and utempter support is no longer compiled by default (intentionally). It is necessary to execute ./configure --enable-utempter in order to make it working again - without it the currently logged-in user is not tracked in tmux sessions correctly. See also https://github.com/tmux/tmux/issues/1006 Version-Release number of selected component (if applicable): All versions of tmux since 2.4. How reproducible: Steps to Reproduce: 1. Install tmux 2. Connect with SSH to the machine with tmux 3. who -m 4. tmux 5. who -m 6. sudo su - 7. who -m Actual results: Empty line in `who -m` after executing `tmux`. Expected results: All `who -m` steps (steps 3, 5 and 7) print line with the same user name. Additional info: