Merge "Add doc for lsblk: /dev/nvme0n1p2: not a block device"

This commit is contained in:
Zuul 2023-01-04 16:17:01 +00:00 committed by Gerrit Code Review
commit 287dbdf019

@ -1010,3 +1010,41 @@ upper limit to the setting.
This was an infrastructure operator requested feature from actual lessons
learned in the operation of Ironic in large scale production. The defaults
may not be suitable for the largest scale operators.
Why do I have an error that an NVMe Partition is not a block device?
====================================================================
In some cases, you can encounter an error that suggests a partition that has
been created on an NVMe block device, is not a block device.
Example:
lsblk: /dev/nvme0n1p2: not a block device
What has happened is the partition contains a partition table inside of it
which is confusing the NVMe device interaction. While basically valid in
some cases to have nested partition tables, for example, with software
raid, in the NVMe case the driver and possibly the underlying device gets
quite confused. This is in part because partitions in NVMe devices are higher
level abstracts.
The way this occurs is you likely had a ``whole-disk`` image, and it was
configured as a partition image. If using glance, your image properties
may have a ``img_type`` field, which should be ``whole-disk``, or you
have a ``kernel_id`` and ``ramdisk_id`` value in the glance image
``properties`` field. Definition of a kernel and ramdisk value also
indicates that the image is of a ``partition`` image type. This is because
a ``whole-disk`` image is bootable from the contents within the image,
and partition images are unable to be booted without a kernel, and ramdisk.
If you are using Ironic in standalone mode, the optional
``instance_info/image_type`` setting may be advisable to be checked.
Very similar to Glance usage above, if you have set Ironic's node level
``instance_info/kernel`` and ``instance_info/ramdisk`` parameters, Ironic
will proceed with deploying an image as if it is a partition image, and
create a partition table on the new block device, and then write the
contents of the image into the newly created partition.
.. NOTE::
As a general reminder, the Ironic community recommends the use of
whole disk images over the use of partition images.