Use the following commands to install the components:
checks
cp /opt/omd/sites/SITENAME/share/doc/check_mk/treasures/modbus/checks/* /opt/omd/sites/SITENAME/share/check_mk/checks/
checkman
cp /opt/omd/sites/SITENAME/share/doc/check_mk/treasures/modbus/checkman/* /opt/omd/sites/SITENAME/share/check_mk/checkman/
agents
cp /opt/omd/sites/SITENAME/share/doc/check_mk/treasures/modbus/agents/special* /opt/omd/sites/SITENAME/share/check_mk/agents/special/
wato
cp /opt/omd/sites/SITENAME/share/doc/check_mk/treasures/modbus/wato* /opt/omd/sites/SITENAME/share/check_mk/web/plugins/wato/