This is an upgrade from 42.3, not a true install. The major bug is reported at
the end: ERROR: failed to lookup root id: Inappropriate ioctl for device

I had many problems, so had to employ chroot get the /grub2/device.map etc. set
so that grub2-mkconfig would run. This system was running 42.3 so many
conditions previously ignored became critical errors in 15.0. I would hope that
non critical issues could be posted as notes and ignored so one is not left
with a system that will not boot.

The output from my grub2-mkconfig command follows.

grub2-mkconfig -o /boot/grub2/grub.cfg 
Generating grub configuration file ...
Found theme: /boot/grub2/themes/openSUSE/theme.txt
Found linux image: /boot/vmlinuz-4.12.14-lp150.12.4-default
Found initrd image: /boot/initrd-4.12.14-lp150.12.4-default
Found linux image: /boot/vmlinuz-4.4.126-48-default
Found initrd image: /boot/initrd-4.4.126-48-default
Found linux image: /boot/vmlinuz-4.4.79-19-default
Found initrd image: /boot/initrd-4.4.79-19-default
Found linux image: /boot/vmlinuz-3.16.7-7-desktop
Found initrd image: /boot/initrd-3.16.7-7-desktop
  WARNING: Not using lvmetad after response error.
Found Windows 7 on /dev/sda1
Found openSUSE Leap 15.0 on /dev/sdb2
Found openSUSE Leap 42.3 on /dev/sdd2
ERROR: failed to lookup root id: Inappropriate ioctl for device

output of hwinfo for the disk is (abbreviated):
IDE 500.0: 10600 Disk
  [Created at block.245]
  Unique ID: _kuT.BVF64zRbVj6
  Parent ID: w7Y8.MOsD+3QQ1xE
  SysFS ID: /class/block/sdc
  SysFS BusID: 5:0:0:0
  SysFS Device Link:
/devices/pci0000:00/0000:00:1f.2/ata6/host5/target5:0:0/5:0:0:0
  Hardware Class: disk
  Model: "Samsung SSD 840"
  Vendor: "Samsung"
  Device: "SSD 840"
  Revision: "2B6Q"
  Driver: "ahci", "sd"
  Driver Modules: "ahci", "sd_mod"
  Device File: /dev/sdc
  Device Files: /dev/sdc,
/dev/disk/by-id/ata-Samsung_SSD_840_EVO_1TB_mSATA_S1KRNEAFC02617H,
/dev/disk/by-id/scsi-0ATA_Samsung_SSD_840_S1KRNEAFC02617H,
/dev/disk/by-id/scsi-1ATA_Samsung_SSD_840_EVO_1TB_mSATA_S1KRNEAFC02617H,
/dev/disk/by-id/scsi-35002538844584d30,
/dev/disk/by-id/scsi-SATA_Samsung_SSD_840S1KRNEAFC02617H,
/dev/disk/by-id/scsi-SATA_Samsung_SSD_840_S1KRNEAFC02617H,
/dev/disk/by-id/wwn-0x5002538844584d30,
/dev/disk/by-path/pci-0000:00:1f.2-ata-6,
/dev/disk/by-path/pci-0000:00:1f.2-scsi-5:0:0:0
  Device Number: block 8:32-8:47
  BIOS id: 0x82
  Drive status: no medium
  Config Status: cfg=new, avail=yes, need=no, active=unknown
  Attached to: #16 (SATA controller)

I do not know what the missing ioctl is or where it would look for it. I hope
this is enough data, and not too much:-) Thanks for your help.
Don