if you are running 100% on your root file system, lots of system service will malfunction, and we need to immediately expand the volume and add more space to file system.
a quick way to tell whether a port is being used in Linux
python3 -m http.server 8080 --bind 0.0.0.0
when port is available, it shows
Serving HTTP on 0.0.0.0 port 8081 (http://0.0.0.0:8081/) ...
troubleshooting SSH remote login failure with public key
Before