Use sudo su to login without any password prompt

Step 1

Edit sudoers file with command visudo:

$ visudo

You should get something similar to this content:

#
# 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

Step 2

Find %sudo entry, and and update last part of ALL:

%sudo ALL=(ALL:ALL) NOPASSWD:ALL

Step 3

Now add your user to the sudo group:

$ usermod -a -G sudo {your_user_name}

Exit and re-login to the shell. Now you can use:

$ sudo su -