How to run sudo command without prompting password:

1. Create backup of /etc/sudoers:

    $ sudo cp /etc/sudoers /etc/sudoers.bak
   

2. Then, using nano/vi to edit the /etc/sudoers file.

    $ sudo visudo
   

   By default visudo using vi editor, but if you want to use nano (for example).

   It will show similar like this and enter your preferred editor.

    $ sudo update-alternatives --config editor
   
    There are 4 choices for the alternative editor (providing /usr/bin/editor).
    Selection    Path                Priority   Status
    ------------------------------------------------------------
    * 0          /bin/nano            40        auto mode
    1            /bin/ed             -100       manual mode
    2            /bin/nano            40        manual mode
    3            /usr/bin/vim.basic   30        manual mode
    4            /usr/bin/vim.tiny    15        manual mode
   
    Press <enter> to keep the current choice[*], or type selection number:
   

3. Add or Edit your user to add the NO PASSWD privilege. It will show similar like this.

   
    # This file MUST be edited with the 'visudo' command as root.
    #
    # Please consider adding local content in /etc/sudoers.d/ instead of
    # directly modifying this file.
    #
    # See the man page for details on how to write a sudoers file.
    #
    Defaults    env_reset
    Defaults    mail_badpass
    Defaults    secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"
   
    # Host alias specification
   
    # User alias specification
   
    # Cmnd alias specification
   
    # User privilege specification
    root    ALL=(ALL:ALL) ALL
   
    # Members of the admin group may gain root privileges
    %admin ALL=(ALL) ALL
   
    # Allow members of group sudo to execute any command
    %sudo   ALL=(ALL:ALL) ALL
   
    # See sudoers(5) for more information on "#include" directives:
   
    #includedir /etc/sudoers.d
    $USER ALL=(ALL) NOPASSWD: ALL # $USER is your user in Unix/Linux host.
   

4. To give it a try, you can save the new /etc/sudoers file and do:

    $ sudo su
    root@your-pc-name:/home/user#