[Bug 1893775] Comment bridged from LTC Bugzilla

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------- Comment From MIHAJLOV at de.ibm.com 2020-09-02 08:24 EDT-------
To add to Frank's comment. /dev/vda is the correct node for DASDs attached using virtio-blk. It is necessary to observe the disk label, e.g using parted /dev/vda print which yields an output like

Model: Virtio Block Device (virtblk)
Disk /dev/vda: 22.2GB
Sector size (logical/physical): 4096B/4096B
Partition Table: dasd
Disk Flags:

Number  Start   End     Size    File system     Flags
1      3146kB  318MB   315MB   ext2
2      318MB   20.4GB  20.0GB  btrfs
3      20.4GB  22.2GB  1790MB  linux-swap(v1)

It seems that the new installer always tries to write a GPT disk label,
which is wrong and renders the disk unusable.

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Title:
  [UBUNTU 20.04.1] Failure to install Ubuntu 20.04.1 as KVM guest on
  DASD

Status in Ubuntu on IBM z Systems:
  Triaged
Status in subiquity package in Ubuntu:
  New
Status in subiquity source package in Focal:
  New
Status in subiquity source package in Groovy:
  New

Bug description:
  ---Problem Description---
  Failure to install Ubuntu 20.04.1 as KVM guest on DASD
    
  ---uname output---
  Linux version 5.4.0-42-generic (buildd at bos02-s390x-003) (gcc version 9.3.0 (Ubuntu 9.3.0-10ubuntu2)) #46-Ubuntu SMP Fri Jul 10 00:21:32 UTC 2020 (Ubuntu 5.4.0-42.46-generic 5.4.44)
   
  Machine Type = 3096-703 
   
  ---boot type---
  CDROM / ISO image
   
  ---Install repository type---
  Internet repository
   
  ---Install repository Location---
  ports.ubunut.com
   
  ---Point of failure---
  Other failure during installation (stage 1)

  I tried to install an Ubuntu 20.04.1 guest from ISO which failed.
  Steps to reproduce.
  1. Boot from ISO to start installer, in my case I used virt-install, but a manually defined libvirt domain has the same issue:
  $ virt-install --name focal.1 --memory 2048 --disk path=/dev/disk/by-path/ccw-0.0.a03f --cdrom ubuntu-20.04.1-live-server-s390x.iso

  2. On the installer screen, stay in simple mode and accept all
  defaults

  3. Shortly after a error pop-up appears, saying the installation has failed. Opening the log I see:
  ...
   storage:
     config:
     - {ptable: gpt, path: /dev/vda, wipe: superblock-recursive, preserve: false, name: '',
       grub_device: false, type: disk, id: disk-vda}
     - {device: disk-vda, size: 22153265152, wipe: superblock, flag: '', number: 1, preserve: false,
       type: partition, id: partition-0}
     - {fstype: ext4, volume: partition-0, preserve: false, type: format, id: format-0}
     - {device: format-0, path: /, type: mount, id: mount-0}
     version: 1
  ...
  An error occured handling 'format-0': OSError - could not get path to dev from kname: vda1
   finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: configuring format: format-0
   TIMED BLOCK_META: 1.942
   finish: cmd-install/stage-partitioning/builtin/cmd-block-meta: FAIL: curtin command block-meta

  
  It seems that the new installation procedure isn't correctly detecting virtio-attached DASDs and tries to handle them like SCSI disks (gpt label, ...). This is a regression compared to the debian-installer and prevents the installation of Ubuntu 20.04 KVM guests on DASD.

  I cross-checked by running the installation on a QCOW2 image, which
  succeeded without problems.

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