been implemented through the multiple lower layers feature of OverlayFS.
+ZIPL
+~~~~
+**rd.zipl=**__<path to blockdevice>__::
+ Update the dracut commandline with the values found in the
+ _dracut-cmdline.conf_ file on the given device.
+ The values are merged into the existing commandline values
+ and the udev events are regenerated.
++
+[listing]
+.Example
+--
+rd.zipl=UUID=0fb28157-99e3-4395-adef-da3f7d44835a
+--
+
Plymouth Boot Splash
~~~~~~~~~~~~~~~~~~~~
**plymouth.enable=0**::
--- /dev/null
+#!/bin/bash
+
+DEV=$1
+MNT=/boot/zipl
+
+if [ -z "$DEV" ] ; then
+ echo "No IPL device given"
+ > /tmp/install.zipl.cmdline-done
+ exit 1
+fi
+
+[ -d ${MNT} ] || mkdir -p ${MNT}
+
+mount -o ro ${DEV} ${MNT}
+if [ "$?" != "0" ] ; then
+ echo "Failed to mount ${MNT}"
+ > /tmp/install.zipl.cmdline-done
+ exit 1
+fi
+
+if [ -f ${MNT}/dracut-cmdline.conf ] ; then
+ cp ${MNT}/dracut-cmdline.conf /etc/cmdline.d/99zipl.conf
+fi
+
+umount ${MNT}
+
+if [ -f /etc/cmdline.d/99zipl.conf ] ; then
+ systemctl restart dracut-cmdline.service
+ systemctl restart systemd-udev-trigger.service
+fi
+> /tmp/install.zipl.cmdline-done
+
+exit 0
--- /dev/null
+#!/bin/bash
+# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
+# ex: ts=8 sw=4 sts=4 et filetype=sh
+
+# called by dracut
+check() {
+ local _arch=$(uname -m)
+ # Only for systems on s390 using indirect booting via userland grub
+ [ "$_arch" = "s390" -o "$_arch" = "s390x" ] || return 1
+ # /boot/zipl contains a first stage kernel used to launch grub in initrd
+ [ -d /boot/zipl ] || return 1
+ return 0
+}
+
+# called by dracut
+depends() {
+ echo grub2
+ return 0
+}
+
+# called by dracut
+installkernel() {
+ instmods ext2
+}
+
+# called by dracut
+cmdline() {
+ local _boot_zipl
+
+ _boot_zipl=$(sed -n 's/\(.*\)\w*\/boot\/zipl.*/\1/p' /etc/fstab)
+ if [ -n "$_boot_zipl" ] ; then
+ echo "rd.zipl=${_boot_zipl}"
+ fi
+}
+
+# called by dracut
+install() {
+ inst_multiple mount umount
+
+ inst_hook cmdline 91 "$moddir/parse-zipl.sh"
+ inst "${moddir}/install_zipl_cmdline.sh" /sbin/install_zipl_cmdline.sh
+ if [[ $hostonly_cmdline == "yes" ]] ; then
+ local _zipl=$(cmdline)
+
+ [[ $_zipl ]] && printf "%s\n" "$_zipl"
+ fi
+ dracut_need_initqueue
+}
--- /dev/null
+#!/bin/sh
+# -*- mode: shell-script; indent-tabs-mode: nil; sh-basic-offset: 4; -*-
+# ex: ts=8 sw=4 sts=4 et filetype=sh
+
+zipl_arg=$(getarg rd.zipl)
+
+if [ -n "$zipl_arg" ] ; then
+ case "$zipl_arg" in
+ LABEL=*) \
+ zipl_env="ENV{ID_FS_LABEL}"
+ zipl_val=${zipl_arg#LABEL=}
+ zipl_arg="/dev/disk/by-label/${zipl_val}"
+ ;;
+ UUID=*) \
+ zipl_env="ENV{ID_FS_UUID}"
+ zipl_val=${zipl_arg#UUID=}
+ zipl_arg="/dev/disk/by-uuid/${zipl_val}"
+ ;;
+ /dev/mapper/*) \
+ zipl_env="ENV{DM_NAME}"
+ zipl_val=${zipl_arg#/dev/mapper/}
+ ;;
+ /dev/disk/by-*) \
+ zipl_env="SYMLINK"
+ zipl_val=${zipl_arg#/dev/}
+ ;;
+ /dev/*) \
+ zipl_env="KERNEL"
+ zipl_val=${zipl_arg}
+ ;;
+ esac
+ if [ "$zipl_env" ] ; then
+ {
+ printf 'ACTION=="add|change", SUBSYSTEM=="block", %s=="%s", RUN+="/sbin/initqueue --settled --onetime --unique /sbin/install_zipl_cmdline.sh %s"\n' \
+ ${zipl_env} ${zipl_val} ${zipl_arg}
+ echo "[ -f /tmp/install.zipl.cmdline-done ]" >$hookdir/initqueue/finished/wait-zipl-conf.sh
+ } >> /etc/udev/rules.d/99zipl-conf.rules
+ cat /etc/udev/rules.d/99zipl-conf.rules
+ fi
+ wait_for_dev -n "$zipl_arg"
+fi