iDRAC Firmware for R340 with CentOS 6.9

If you do not have a supported operating system installed, you can use iDRAC only to update the FW. Updating using iDRAC is OS agnostic. You can download "iDRAC-with-Lifecycle-Controller_Firmware_WPNPP_WN64_5.10.30.00_A00.EXE" file from below link and use iDRAC only to update the FW

https://www.dell.com/support/home/en-us/drivers/driversdetails?driverid=wpnpp&productcode=poweredge-r340 

You can refer below link for details on updating FW using iDRAC

https://www.dell.com/support/kbdoc/en-in/000134013/dell-poweredge-update-the-firmware-of-single-system-components-remotely-using-the-idrac