Sudo cannot be used

Sudo cannot be used. After installing the system today, I found that my sudo command is not working properly. The general situation is as follows :....... we trust you have got ed the usual lecture from the local System Administrator. it usually boils down to these three things: #1) Respect the privacy of others. #2) Think before you type. #3) With great power comes great responsibility ....... later, I found the relevant information on the Internet. The specific solution is as follows: 1. log on to the root mode using su-2. Change the sudoers permission of the file to writable: chmod 740/etc/sudoers3, use vi to open the sudoers file: vi/etc/sud Oers4, press enter at root ALL = (ALL) ALL, write username ALL = (ALL) ALL5 in another line, save and exit 6, and change sudoers permission to the default 440: chmod 440/etc/sudoers7, exit root to normal user mode, use sudo test, pass! Note: If you do not need to enter the password when using sudo, you can change the four fields to: username ALL = NOPASSWD: ALL. Complete example: #/etc/sudoers # This file MUST be edited with the 'usually do 'command as root. # See the man page for details on how to write a sudoers file. # Defaults env_reset # Host alias specification # User alias specification # Cmnd alias specification # User privilege specification root ALL = (ALL) ALL # tiger ALL = (ALL) ALL tiger ALL = NOPASSWD: ALL # Uncomment to allow members of group sudo to not need a password # (Note that later entries override this, so you might need to move # it further down) # % sudo ALL = NOPASSWD: ALL