#!/bin/bash
#Reference: https://www.digitalocean.com/community/tutorials/how-to-install-mysql-on-centos-7

#Note: Don't use : in passwords, because a wizzard used later, makes use of : as seperators
#1: Define variable with the password
MYSQL_PASS="Percent-Gope-Dumping-Uninsured-Maybe4"

#2: ... if the short hostname is usrXX-hn01 before continuing
hostname -s|grep "usr[0-9]\{2\}-hn[0-9]*"
if [ $? -ne 0 ]; then
        echo "This script should be executed on the Head Node only"
        exit 1
fi

#4: Install MySQL as on the webpage
curl -sSLO https://dev.mysql.com/get/mysql80-community-release-el7-5.noarch.rpm
if [ "$(md5sum mysql80-community-release-el7-5.noarch.rpm|sed 's| .*||g')" == "e2bd920ba15cd3d651c1547661c60c7c" ]; then
        #Note the -y options used, so as per #3 in the assignemet, no user intervention is required
        yum -y localinstall mysql80-community-release-el7-5.noarch.rpm   &&  yum -y install mysql-server
else
        echo "The md5sum values don't match. We won't continue..."
        exit 2
fi

#5: Enable the service and start it automatically after reboots:
sudo systemctl enable mysqld --now

#6: Read the content of the temporary password into a variable:
temp_pass=$(cat /var/log/mysqld.log |grep -i "A temporary password" |sed "s|.*: ||g")

#7: Create the here document
cat > secure_mysql.sql <<-EOF
ALTER USER 'root'@'localhost' IDENTIFIED BY '$MYSQL_PASS';
DELETE FROM mysql.user WHERE User='root' AND Host NOT IN ('localhost', '127.0.0.1', '::1');
DELETE FROM mysql.user WHERE User='';
DELETE FROM mysql.db WHERE Db='test' OR Db='test_%';
FLUSH PRIVILEGES;
EOF

#8: Create a here document ~/my.cnf
cat > ~/.my.cnf <<EOF
[mysql]
user=root
password=$temp_pass
EOF

#9: Execute the mysql command using the root user and the temp password:
mysql --connect-expired-password  < secure_mysql.sql

#10: If the above was successful, delete the secure_mysql.sql file:
[ $? -eq 0 ] && /bin/rm secure_mysql.sql

#11: Change the password in the ~/.my.cnf file
sed -i "s|^password=.*|password=$MYSQL_PASS|g" ~/.my.cnf