Processor manufacturers release stability and security updates to the processor microcode. While microcode can be updated through the BIOS, the Linux kernel is also able to apply these updates. These updates provide bug fixes that can be critical to the stability of your system. Without these updates, you may experience spurious crashes or unexpected system halts that can be difficult to track down.

The microcode loader supports three loading methods:

  • Early load microcode
  • Late loading
  • Builtin microcode

You can get more details from here.

RancherOS supports Late loading. To update the Intel microcode, get the latest Intel microcode. An example is here. Then copy the data files to the firmware directory:

mkdir -p /lib/firmware/intel-ucode/
cp -v intel-ucode/* /lib/firmware/intel-ucode/

Reload the microcode. This file does not exist if you are running RancherOS on the hypervisor. Usually, the VM does not need to update the microcode.

echo 1 > /sys/devices/system/cpu/microcode/reload

Check the result:

dmesg | grep microcode
[   13.659429] microcode: sig=0x306f2, pf=0x1, revision=0x36
[   13.665981] microcode: Microcode Update Driver: v2.01 <>, Peter Oruba
[  510.899733] microcode: updated to revision 0x3b, date = 2017-11-17

You can use runcmd to reload the microcode every boot:

- echo 1 > /sys/devices/system/cpu/microcode/reload