Adding a new user and password for a user
$ adduser demouser
$ passwd demouser
Double check the user file
$ vi /etc/demouser.conf
Lock the user account pwd so that there is no future access
$ passwd --lock demouser
Find out all running processes of user account PIDs (Process IDs)
$ pgrep -u demouser
List the processes username, PIDs, PPIDs, terminal used, proc state, cmd path
$ ps -f --pid $(pgrep -u demouser)
Kill all process by the username
$ killall -9 -u demouser
Backup user data if needed
$ tar jcvf /user-backups/demouser-home-directory-backup.tar.bz2 /home/demouser
Delete user and home directory
$ deluser --remove-home demouser
Delete user and all files
$ deluser --remove-all-files demouser