If I open up a new tmux session, /var/log/wtmp
does not seem to get updated with the new session. This can be observed by setting up watch "last -n 10"
in one window, and then starting up a new tmux session in another. There’s no login getting logged, at least as far as last
can tell.
A little googling turned up Bug #1890406 “tmux sessions don't show up with who, users, ...” : Bugs : tmux package : Ubuntu, which appears to be basically the same bug report but on Ubuntu. They suggest that this was a tmux bug fixed in a later version. However running with the latest tmux version (3.2a at the time of writing, also latest on nixpkgs-unstable) doesn’t fix the issue for me.