What were you trying to do that didn't work?

During the IPU of RHEL X systems, it's common that kernel cmdline parameters needs to be updated for the RHEL X+1 kernels. Some typical changes happening during the upgrade:

• IPU 7 -> 8, sometimes requires adding `net.ifnames=0` kernel cmdline to keep eth0 NIC name on VM with only this one network interface. Dropping this argument on RHEL 8+ kernel means my NIC will be renamed e.g. to enc0.
• IPU 8 -> 9 requires updated value of crashkernel parameter when kdump is used

When installing another kernel on the system upgraded by leapp, in some cases the newly installed kernel has old kernel cmdline which leads to inconsistent behaviour
when booting into such a kernel.

How reproducible:

On some upgraded system. We see different behaviour based on architecture, original RHEL release, upgraded RHEL release, and possibly also on the bootloader configuration. Cannot say for sure what are all differences.

Steps to reproduce

1. leapp upgrade
2. dnf update # or just install whatever different kernel version from the upgraded system if no newer kernel is present

Expected results

Newly installed kernels have up-to-date kernel cmdline

Actual results

Updating kernel packages using `dnf update` creates new boot entries with obsoleted kernel cmdline parameters.

Workarounds:

• After the upgrade, on RHEL 9 (all architectures) or RHEL 8 for IBM Z:

  # BOOT_OPTIONS="$(tr -s "$IFS" '\n' </proc/cmdline | grep -ve '^BOOT_IMAGE=' -e '^initrd=' | tr '\n' ' ')"
  # echo $BOOT_OPTIONS > /etc/kernel/cmdline
  

• After the upgrade, on RHEL 8 all architectures but IBM Z:

  # BOOT_OPTIONS="$(tr -s "$IFS" '\n' </proc/cmdline | grep -ve '^BOOT_IMAGE=' -e '^initrd=' | tr '\n' ' ')"
  # grub2-editenv - set "kernelopts=$BOOT_OPTIONS"