How to update microcode on RancherOS

content/os/v1.x/en/about/microcode-loader/_index.md

@@ -0,0 +1,44 @@
+---
+title: How to update microcode
+weight: 306
+---
+
+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](https://www.kernel.org/doc/html/latest/x86/microcode.html).
+
+RancherOS can support `Late loading`, here are the steps to update Intel microcode, you can refer to:
+
+```
+# we can get the latest intel microcode, such as https://downloadcenter.intel.com/download/28087/Linux-Processor-Microcode-Data-File?v=t
+# then we need to copy data files to firmware dir
+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 ROS 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 <tigran@aivazian.fsnet.co.uk>, Peter Oruba
+[  510.899733] microcode: updated to revision 0x3b, date = 2017-11-17
+```
+
+You can use `runcmd` to reload microcode every boot:
+
+```
+runcmd:
+- echo 1 > /sys/devices/system/cpu/microcode/reload
+```