This assumes a local file such as
n23ur33w.iso downloaded from the Lenovo support website (e.g. from https://support.lenovo.com/fr/en/downloads/DS502281).
geteltorito to extract the relevant boot image from the ISO file (following the “El Torito” standard):
$ sudo dnf install geteltorito ... $ geteltorito -o lenovo-bios.img n23ur33w.iso Booting catalog starts at sector: 20 Manufacturer of CD: NERO BURNING ROM VER 12 Image architecture: x86 Boot media type is: harddisk El Torito image starts at sector 27 and has 67584 sector(s) of 512 Bytes Image has been written to file "lenovo-bios.img".
Write the data as-is onto the thumb drive (in my case the thumb drive is
/dev/sda, as discovered with
$ sudo dd if=lenovo-bios.img of=/dev/sda 67584+0 records in 67584+0 records out 34603008 bytes (35 MB, 33 MiB) copied, 3.7256 s, 9.3 MB/s
The result is a bootable thumb drive via which you can perform the desired update operation.
At the time of writing, popular tools such as rufus do not offer a one-click solution for creating a bootable thumb drive straight from the ISO file offered by Lenovo. Context and discussion can be found at https://github.com/pbatard/rufus/issues/63.