[Unit]
Description=Set random password for user root
DefaultDependencies=no
After=local-fs.target
Before=getty@tty1.service

[Service]
Type=oneshot
ExecStart=/bin/sh -c 'echo "root:$(openssl rand -base64 48)" | chpasswd'
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target