proxysql/systemd/system/proxysql-initial.service

[Unit]
Description=High Performance Advanced Proxy for MySQL, this service will reset the database and start ProxySQL
After=network.target

[Service]
Type=oneshot
ExecStartPre=/bin/systemctl set-environment PROXYSQL_OPTS="--initial"
ExecStart=/bin/systemctl start proxysql
ExecStartPost=/bin/systemctl unset-environment PROXYSQL_OPTS
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target