Commands

Find name of the process running on a port

lsof -i :portnumber

lsof -i tcp:portnumber

lsof -i udp:portnumber

fuser portnumber/tcp

netstat -tulpn | grep :portnumber

Find owner of a process

ps -ef | grep PID

ps -p PID (gives name of the command that started this process)

Current working directory of a process

pwdx PID

alternatively, you can browse through /proc/PID/cwd

Find name of the package responsible for a command

dpkg -S /bin/ls

link