Set default root password for MySQL 5.7 with Ubuntu when MySQL doesn't ask for root password at installing

mysql_native_password.sh

#!/bin/sh
# |           THIS SCRIPT IS TESTED CORRECTLY ON           |
# |--------------------------------------------------------|
# | OS     | MySQL                    | Test | Last test   |
# |--------|--------------------------|------|-------------|
# | Ubuntu | Ver 14.14 Distrib 5.7.26 | OK   | 16 May 2019 |

MYSQL_ROOT_PASSWORD=`head /dev/urandom | tr -dc A-Za-z0-9 | head -c10`
sudo mysql -uroot<<EOF 
use mysql;
update user set authentication_string=password('$MYSQL_ROOT_PASSWORD') where user='root'; 
update user set plugin="mysql_native_password" where User='root';
flush privileges;
EOF
(mysql -uroot -p$MYSQL_ROOT_PASSWORD -e ";") >/dev/null 2>&1 && {
    echo -e "\033[33m[INFO] Temporary password for your mysql's user root: $MYSQL_ROOT_PASSWORD\033[0m"
    echo "[INFO] You can excute mysql_secure_installation to change ..."
}

Use below command to set default root password for MySQL 5.7 with Ubuntu on your own operating system.
wget -O - https://gist.githubusercontent.com/syneart/d615ba2a87e2f8b24a2a3aeb53f73d67/raw/mysql_native_password.sh | sh