prepare the floppy image file that later can be mounted via AMT, include in it just the bios update file – in my case it was PET20A18.exe from here.
mkfs.msdos -C /tmp/imagefile.img 14400 mkdir /media/floppy1/ mount -o loop /path/imagefile.img /media/floppy1/ cd /media/floppy1/ wget https://downloads.dell.com/FOLDER05054865M/1/PET20A18.exe cd .. umount /media/floppy1/
once the file is ready use the Manageability Commander Tool > Remote Control > Take control mount such img file as a virtual, oversize floppy. Using the Launch Viewer connect via VNC, keep on pressing F12 while rebooting server and select from the boot menu ‘BIOS Flash Update’.
click on the … icon and select the bios image from the virtual floppy.
let it reboot, wait 5 minutes and the bios update is finished.