I have spend many fees to different different institute to understand the Linux....but your simplest way of explaining the concept of user management is the best.....which crystal clear my doubts especially the last one on shells assigning to the users...really much appreciated to you sir.....thank you for your utmost help...
sir with vim /etc/passwd command ihave changed user test:x:1005:1006::/home/test:/bin/ksh while enter su - test command I am getting the below error. su: failed to execute /bin/ksh: No such file or directory