[Bug 1845571] Re: ubiquity offers installation media as an install target

[Dimitri John Ledkov]

** Description changed:

  I guess this is actually a bug in some partman component, but well. In
  both the desktop and ubuntu studio installers for eoan beta, I was
  offered the installation media as a target disk. This seems unlikely to
  be correct.
+ 
+ ==
+ 
+ partman-auto must not use the _whole_ device, of anything that is
+ mounted on /cdrom.
+ 
+ Our ISOs are multipartition eltorito devices. And one can mount the top-
+ level device, or the first partition, to get the same content (depending
+ if one knows how to read partitions that is). Previously we were
+ mounting the top-level /dev/sda, but now we started to mount /dev/sda1,
+ unbreaking using other partitions of the installer media for purposes of
+ persistence & installer logs.
+ 
+ Partman & parted are actually very confused by our installer media, as
+ they get tricked by -isohybrid-apm-hfsplus into thinking it is MAC based
+ partition table, when in fact it's just MS-DOS or GPT depending how one
+ looks at it. At least blkid/udevadm correctly declare it el-torito
+ hybrid image.
+ 
+ Thus when parted init code tries to walk the partitions, and detect
+ installer media mounts none of that code actually runs, as no partitions
+ are detected partman (and parted_devices declares it unknown partition
+ table).
+ 
+ Hence I guess, the static strict check for the "whole $device mount on
+ /cdrom" was added.
+ 
+ But given the above change to mount just a partition this has now
+ started to fail. Imho we should expand the pattern to match at least
+ optionally match 'p?[0-9]*' - depending on how one re-rolls the iso, it
+ may or may not be multipartition one, with optionally 'p'-prefixed
+ (hello nvme) partition number, such that all of these cases are valid.

** Attachment added: "test.sh"
   https://bugs.launchpad.net/ubuntu/+source/partman-auto/+bug/1845571/+attachment/5296101/+files/test.sh

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https://bugs.launchpad.net/bugs/1845571

Title:
  ubiquity offers installation media as an install target

Status in partman-auto package in Ubuntu:
  Triaged
Status in partman-auto source package in Eoan:
  Triaged

Bug description:
  I guess this is actually a bug in some partman component, but well. In
  both the desktop and ubuntu studio installers for eoan beta, I was
  offered the installation media as a target disk. This seems unlikely
  to be correct.

  ==

  partman-auto must not use the _whole_ device, of anything that is
  mounted on /cdrom.

  Our ISOs are multipartition eltorito devices. And one can mount the
  top-level device, or the first partition, to get the same content
  (depending if one knows how to read partitions that is). Previously we
  were mounting the top-level /dev/sda, but now we started to mount
  /dev/sda1, unbreaking using other partitions of the installer media
  for purposes of persistence & installer logs.

  Partman & parted are actually very confused by our installer media, as
  they get tricked by -isohybrid-apm-hfsplus into thinking it is MAC
  based partition table, when in fact it's just MS-DOS or GPT depending
  how one looks at it. At least blkid/udevadm correctly declare it el-
  torito hybrid image.

  Thus when parted init code tries to walk the partitions, and detect
  installer media mounts none of that code actually runs, as no
  partitions are detected partman (and parted_devices declares it
  unknown partition table).

  Hence I guess, the static strict check for the "whole $device mount on
  /cdrom" was added.

  But given the above change to mount just a partition this has now
  started to fail. Imho we should expand the pattern to match at least
  optionally match 'p?[0-9]*' - depending on how one re-rolls the iso,
  it may or may not be multipartition one, with optionally 'p'-prefixed
  (hello nvme) partition number, such that all of these cases are valid.

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