I have seen people use passwd -l $USERNAME ,But the linux man page does not explain what the -l option is for. What does it do ?
What is -l option do to the passwd command?
password
I got this by issuing the passwd command at the CLI-l, --lock                    lock the password of the named accountIt locks the account so that root has to unlock the account before this person can log-in and use the account again.EDIT As it was indicated this is a duplicate of this