Thinkpad: Upgrade Bios using Linux

Posted on Feb 28, 2020

So I was trying to upgrade the BIOS the other day and I thought it’d be good to document it for future - since I plan on getting a Thinkpad X220 and patching the BIOS (maybe even going the coreboot route). Anyways, here’s the steps.


  • Grab the iso from support site
  • Convert iso to usb and write it to disk
  • Restart and boot into USB drive (Make sure legacy boot is enabled BIOS).
  • Run through instructions and update the BIOS.

thinkpad t420s ready for bios update

  1. Download the latest BIOS update from or just search “bios update lenovo ”. Here’s the BIOS download link for Thinkpad T420s
  2. Check your current version with dmidecode and validate that you’re not already up to date. ❯ sudo dmidecode -s bios-version 8CET66WW (1.39 )
  3. To create a bootable USB - convert ISO to IMG file. I recommend using geteltorito which is available for arch or for debian as genisoimage package. Install it using your package manager and then run.

    ❯ -o bios.img /path/to/your-downloaded-file.iso
    Booting catalog starts at sector: 20
    Manufacturer of CD: NERO BURNING ROM
    Image architecture: x86
    Boot media type is: harddisk
    El Torito image starts at sector 27 and has 63488 sector(s) of 512 Bytes
    Image has been written to file "bios.img".
  4. Now that you’ve written to bios.img, attach your USB and use fdisk to see the letter assigned to the drive.

    ❯ lsblk -p
    /dev/sda      8:0    0 149.1G  0 disk
    ├─/dev/sda1   8:1    0   300M  0 part /boot/efi
    └─/dev/sda2   8:2    0 148.8G  0 part /
    /dev/sdb      8:16   1  14.7G  0 disk
    └─/dev/sdb1   8:17   1    31M  0 part

    In our scenario, the drive is /dev/sdb. Validate that none of the partitions contain a mount under MOUNTPOINT column. If they do, unmount each of them with umount /dev/sdbX where X is the partition number ex: umount /dev/sdb1

  5. Write the img file to USB with dd. Provide the if argument your /path/to/bios.img file and of argument your USB drive name - ex: /dev/sdb. You can provide optional status=progress argument to get progress output.

    ❯ sudo dd if=bios.img of=/dev/sdb bs=1M 
    31+0 records in
    31+0 records out
    32505856 bytes (33 MB, 31 MiB) copied, 4.72535 s, 6.9 MB/s
  6. Restart your computer and load up BIOS settings to validate that Legacy boot is enabled. Now boot into your USB drive and follow the instructions on screen. Validate that your battery has significant charge and is plugged into AC power. Choose Update system program to update the BIOS.

  7. Wait till the update is complete. thinkpad t420s ready for bios update

  8. BIOS updates may continue to happen even after reboot. Respect that and keep AC power plugged in and continue to follow on-screen instructions! thinkpad t420s ready for bios update

  9. Validate the BIOS has been upgraded by booting back into and running dmidecode.

    ❯ sudo dmidecode -s bios-version
    8CET66WW (1.46 )