Minicom/tmux can be accessed by a user on the command line, but the content on the screen will get replaced by later content, and the old content is no longer accessible. There’s also no logging of timestamps, which journalctl provides. The command:

tmux pipe-pane -o 'cat >>~/tmux.log'

can be used to send output to a log file, but it’s not journald and won’t have those timestamps. When I try having a service process just call minicom and then attach a tmux session, journalctl contains some output, but like this:

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: [6B blob data]

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: Welcome to minicom 2.7.1

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: OPTIONS: I18n

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: Compiled on Aug 13 2017, 15:25:34.

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: Port /dev/ttyACM0

Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: Press CTRL-A Z for help on special keys Jul 25 16:08:29 raspberrypi minicom-monitor.sh[2279]: [6B blob data]

If I add “–output cat”, then the “blob data” gets replaced with content like “ESC[0mESC[10mESC[HESC[J” (content that got intermixed with readable content on tmux.log when I piped to there), but there’s still none of the readable information I get from minicom if I access it on the console. I would have assumed this was a known use case, but haven’t found an example of it being done.