Comment 17 for bug 1830243

Thanks Christian, but when doing so I get:

$ cat /etc/zipl.conf
# This has been modified by the cloud image build process
[defaultboot]
default=ubuntu

[ubuntu]
target = /boot
secure = 1
image = /boot/vmlinuz
parameters = root=LABEL=cloudimg-rootfs
ramdisk = /boot/initrd.img

$ sudo zipl -V
Using config file '/etc/zipl.conf'
Target device information
  Device..........................: fc:00
  Partition.......................: fc:01
  Device name.....................: vda
  Device driver name..............: virtblk
  Type............................: disk partition
  Disk layout.....................: SCSI disk layout
  Geometry - start................: 2048
  File system block size..........: 4096
  Physical block size.............: 512
  Device size in physical blocks..: 16775135
Building bootmap in '/boot'
Adding IPL section 'ubuntu' (default)
  initial ramdisk...: /boot/initrd.img
  signature for.....: /lib/s390-tools/stage3.bin
  kernel image......: /boot/vmlinuz
Error: Could not install Secure Boot IPL records: Missing signature in image file /boot/vmlinuz

So do I really not need a kernel with a signature?
If so how to avoid the break on the missing signature?

@Dimitri - I found none in the archive yet, do you have signed s390x kernel around that could be used?