How to create a bootable USB thumb drive for Lenovo Thinkpad BIOS updates

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).

Use 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 fdisk -l):

$ 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.

Related references: