Comment 10 for bug 1723541

I just ran into this problem during a standard update. It seems very similar but I thought I would post it here. My system is running within an LPAR with no z/VM. Below are the messages I receive.

sudo apt upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
3 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n]
Setting up linux-image-4.15.0-50-generic (4.15.0-50.54) ...
Setting up initramfs-tools (0.130ubuntu3.8) ...
update-initramfs: deferring update (trigger activated)
Setting up linux-firmware (1.173.6) ...
update-initramfs: Generating /boot/initrd.img-4.15.0-50-generic
Using config file '/etc/zipl.conf'
Run /lib/s390-tools/zipl_helper.device-mapper /boot
Error: Unsupported setup: Directory '/boot' is located on a multi-target device-mapper device
Error: Script could not determine target parameters
run-parts: /etc/initramfs/post-update.d//zz-zipl exited with return code 1
dpkg: error processing package linux-firmware (--configure):
 installed linux-firmware package post-installation script subprocess returned error exit status 1
Processing triggers for linux-image-4.15.0-50-generic (4.15.0-50.54) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-4.15.0-50-generic
Error: Unsupported setup: Directory '/boot' is located on a multi-target device-mapper device
Error: Script could not determine target parameters
Using config file '/etc/zipl.conf'
Run /lib/s390-tools/zipl_helper.device-mapper /boot
run-parts: /etc/initramfs/post-update.d//zz-zipl exited with return code 1
run-parts: /etc/kernel/postinst.d/initramfs-tools exited with return code 1
dpkg: error processing package linux-image-4.15.0-50-generic (--configure):
 installed linux-image-4.15.0-50-generic package post-installation script subprocess returned error exit status 1
Processing triggers for initramfs-tools (0.130ubuntu3.8) ...
update-initramfs: Generating /boot/initrd.img-4.15.0-50-generic
Using config file '/etc/zipl.conf'
Run /lib/s390-tools/zipl_helper.device-mapper /boot
Error: Unsupported setup: Directory '/boot' is located on a multi-target device-mapper device
Error: Script could not determine target parameters
run-parts: /etc/initramfs/post-update.d//zz-zipl exited with return code 1
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 linux-firmware
 linux-image-4.15.0-50-generic
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)