Documentation question: UPI OKD installation version > 4.15 with FCOS images instead of SCOS

[albgarcon]

Hi all,

I have a baremetal (UPI) OKD (v4.15) cluster composed by 13 nodes. According to the documentation the jump to 4.16 requires to "swtich" the VMs SO from FCOS to SCOS.

Instead of doing the cluster upgrade (4.15 FCOS -> 4.16 SCOS), I will create a new cluster with a version > 4.16 (most probably fresh installation of OKD 4.19). The question is that according, to the documentation for doing a baremetal (UPI) installation of OKD 4.19, the nodes require FCOS (https://docs.okd.io/4.19/installing/installing_bare_metal/upi/installing-bare-metal.html#installation-minimum-resource-requirements_installing-bare-metal), but if I am not wrong OKD (>=4.16) uses SCOS instead of FCOS.
Reading the OKD Frequently Asked Questions related to version 4.16 -> https://okd.io/docs/project/scos-migration-faq/#platforms there is the following note:
the installer uses rpm-ostree to pivot the nodes from FCOS to SCOS content. We expect to have access to consistent SCOS image builds in the coming months. We will make an announcement when that happens.

I did not find anything later telling that the installer now uses SCOS so am I right and the installation for any OKD version requires first FCOS and later during the installation this SO is switched automatically to SCOS?.

Thank you in advance.
Regards,

[jatinsu]

but if I am not wrong OKD (>=4.16) uses SCOS instead of FCOS

Hi! Yes you are correct, we did switch to SCOS after 4.15. The docs are outdated and should say SCOS and not FCOS, especially in the 4.19 version. Sorry for the confusion

installation for any OKD version requires first FCOS and later during the installation this SO is switched automatically to SCOS?.

Yeah it does require FCOS first, but the upgrade isn't automatic. There's still some manual intervention required (there's a script at the end of the docs page to do do the grunt work for you however).

[pflaeging]

No, it's not more required to install FCOS first.

The following command gives you the download location of the installer ISO:

openshift-install coreos print-stream-json  \\
  | jq -r .architectures.x86_64.artifacts.metal.formats.iso.disk.location

and this is an scos 10 live image ;-)