Description of problem:

Currently Anaconda always adds the kernel command line parameters required to boot the system in the bootloader configuration (e.g. /etc/default/grub or /etc/zipl.conf) and there is no way to build a initrd with "hostonly_cmdline=yes" in dracut configuration which then would avoid having kernel command line parameters.

I fully understand using "hostonly_cmdline=yes" is not recommended, but it may be the only viable way on IBM Z systems because Z has a limitation on the length of the kernel command line (up to
896 bytes).
When, for example, many disks are attached through zFCP and there is multipath, the rd.zfcp arguments, which are already long by default, may just overflow the limitation, as shown in the example below:
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------
rd.zfcp=0.0.0006,0x5005076810165ecc,0x0000000000000000 rd.zfcp=0.0.0006,0x5005076810165ecb,0x0000000000000000 rd.zfcp=0.0.0008,0x5005076810165ecc,0x0000000000000000 rd.zfcp=0.0.0004,0x5005076810165ecc,0x0000000000000000 rd.zfcp=0.0.0008,0x5005076810165ecb,0x0000000000000000 rd.zfcp=0.0.0004,0x5005076810165ecb,0x0000000000000000 rd.zfcp=0.0.0005,0x5005076810175ecc,0x0000000000000000 rd.zfcp=0.0.0005,0x5005076810175ecb,0x0000000000000000 rd.zfcp=0.0.0007,0x5005076810175ecc,0x0000000000000000 rd.zfcp=0.0.0007,0x5005076810175ecb,0x0000000000000000 rd.zfcp=0.0.0009,0x5005076810175ecc,0x0000000000000000 rd.zfcp=0.0.0009,0x5005076810175ecb,0x0000000000000000 rd.zfcp=0.0.000a,0x5005076810165ecc,0x0000000000000000 rd.zfcp=0.0.000a,0x5005076810165ecb,0x0000000000000000 rd.zfcp=0.0.000b,0x5005076810175ecc,0x0000000000000000 rd.zfcp=0.0.000b,0x5005076810175ecb,0x0000000000000000
-------- 8< ---------------- 8< ---------------- 8< ---------------- 8< --------

Additionally, on Z, there are other long arguments, such as "rd.znet=qeth,0.0.0001,0.0.0002,0.0.0003,layer2=1,portno=0" which doesn't help either.

In such case, having this "hostonly_cmdline=yes" could be a fallback solution.
When active, bootloader arguments related to storage should

Version-Release number of selected component (if applicable):

RHEL8

How reproducible:

Always on customer system

Additional info:

A solution for the customer is to use "rd.zdev=no-auto" which avoids having so many "rd.zfcp" parameters, but it's more a workaround than a proper solution.