Notice if a filesystem overwrites a partitioned disk

[bgilbert]

A common configuration error is to create a filesystem over a whole-disk device rather than the partition that was intended:

variant: fcos
version: 1.4.0
storage:
  disks:
  - device: /dev/sdb
    wipe_table: false
    partitions:
    - label: data
  filesystems:
    - device: /dev/sdb
      path: /mnt
      format: ext4
      with_mount_unit: true

Add a warning if a storage.filesystems.device matches a storage.disks.device.

[dustymabe]

I'm wondering if we should even do this warning at the Ignition level (which I think butane also surfaces Ignition warnings). That means the user would actually get the warning on the console because of our recent addition in coreos/fedora-coreos-config#1621

[bgilbert]

Actually, yeah, that's a good point. I'll leave this issue here for now so other people can weigh in, but if there's consensus we can move it over to Ignition.

[jlebon]

This seems relevant to any distro using Ignition, so having this in Ignition directly SGTM!

[bgilbert]

Moved to Ignition.

[jlebon]

Add a warning if a storage.filesystems.path matches a storage.disks.device.

Shouldn't this be:

Add a warning if a storage.filesystems.device matches a storage.disks.device.

? (And the sample Butane config updated accordingly.)

I guess we could check also that path isn't under /dev, but mounting a filesystem there is an odd thing to do so it doesn't seem worth a check.

[bgilbert]

@jlebon Whoops, yes, good catch. 😖

Also, we should probably only warn if there are any storage.disks.partitions. Someone might decide to mention a disk without intending to partition it, and the spec notably does not say that storage.disks is only meant for partitioning. I've just tried it and Ignition does not automatically create a partition table solely because a disk was mentioned, with or without wipeTable.

As a further refinement, we could warn if wipeTable is true but wipeFilesystem is false. That's technically a valid way to recreate the filesystem on every provision, but it's pretty indirect and probably wasn't what the user intended.