It’s pretty easy to see what error messages have been logged on a machine with systemd installed: just run journalctl -p err. But this will show you all of the messages of priority “err” or higher, starting from the beginning of the log. What if you only want the most recent ones?
Again, that’s pretty easy: journalctl -p err -e will do it. The -e parameter tells it to start at the end, not the beginning.
But what if you specifically want to know about error messages that have been logged since you last looked? Enter journal-brief, which keeps a bookmark so that it will only show you messages logged since you last ran it.