RHEL8/zVM: some disk or network devices are missing after upgrading using Leapp from RHEL7

Environment

• Red Hat Enterprise Linux 8 (RHEL8)
  • leapp (upgrade from RHEL7)
  • zVM

Issue

• When upgrading a zVM guest from RHEL7 to RHEL8 using Leapp, some devices (disks or network devices) are not usable and not detected by the kernel

Resolution

1. Enable the device_cio_free.service unit

   # systemctl enable device_cio_free.service
   

2. Reboot the system

   # reboot
   

Root Cause

The issue is due to not enabling the device_cio_free.service unit automatically; this unit is responsible for whitelisting devices after switching root.
The issue is tracked by This content is not included.BZ 2032953 - s390x: leapp post-upgrade doesn't enable "device_cio_free.service" unit, which is required on Z.

Diagnostic Steps

1. Verify that the service isn't enabled

   # systemctl is-enabled device_cio_free.service
   disabled
   

2. Verify that the service didn't execute during boot

   # journalctl -b -u device_cio_free.service
   -- Logs begin at Wed 2021-12-15 08:02:43 EST, end at Wed 2021-12-15 09:34:01 EST. --
   --> nothing printed
   

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