User login process

User login process

Unix booted.

Program Unix(kernel) is booted into main memory, and 

remains active till the computer is shut down

Program init runs as a background task and remains 

running till shutdown

 User attempts to log in.

 Kernel calls program ‘init’.

 ‘init’ scans file /etc/inittab , which lists the ports with 

terminals and their characteristics and returns an 

active open terminal to ‘init’.

 ‘init’ calls program ‘getty’, which issues a login 

prompt in the monitor

 User enters login and password

‘getty’ calls program ‘login’ which scans file /etc/passwd to match username and password

After validation, control passes to session startup program /bin/sh , session startup program

Program /bin/sh reads file /etc/profile and .profile and sets up system wide and user specific environment.

User gets a shell prompt