cloud-init disk_setup fails to partition disk for Ubuntu18

util-linux package version output from dpkg -l :
Version: 2.31.1-0.4ubuntu3.3
Arch: amd64
Name: util-linux

https://marc.info/?l=util-linux-ng&m=142920033601419&w=2

Seems to say this is by-design.

util-linux/fdisk versions in Xenial and newer all have this issue.

The workaround for user-data is to specify:

disk_setup:
  <disk name>:
     layout: [100]

Which will create a single partition spanning the whole disk.

And cloud-init will need to emit ",," as input to sfdisk moving forward.

This should include an integration test in cloud_tests since it involves #cloud-config

On trusty; this complains but works.

ubuntu@ubuntu:~$ dpkg --list | grep util-linux
ii util-linux 2.20.1-5.1ubuntu20.9 amd64 Miscellaneous system utilities
ubuntu@ubuntu:~$ cat /proc/partitions
major minor #blocks name

 253 0 10485760 vda
 253 1 10484736 vda1
 253 16 10485760 vdb
 253 32 366 vdc
  11 0 1048575 sr0
ubuntu@ubuntu:~$ sudo bash
sudo: unable to resolve host ubuntu
root@ubuntu:~# echo "0," | sfdisk --Linux --unit=S --force /dev/vdb
Checking that no-one is using this disk right now ...
OK

Disk /dev/vdb: 20805 cylinders, 16 heads, 63 sectors/track

sfdisk: ERROR: sector 0 does not have an msdos signature
 /dev/vdb: unrecognized partition table type
Old situation:
No partitions found
Warning: bad partition start (earliest 1)
New situation:
Units = sectors of 512 bytes, counting from 0

   Device Boot Start End #sectors Id System
/dev/vdb1 1 20971519 20971519 83 Linux
/dev/vdb2 0 - 0 0 Empty
/dev/vdb3 0 - 0 0 Empty
/dev/vdb4 0 - 0 0 Empty
Warning: no primary partition is marked bootable (active)
This does not matter for LILO, but the DOS MBR will not boot this disk.
Successfully wrote the new partition table

Re-reading the partition table ...

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1)
to zero the first 512 bytes: dd if=/dev/zero of=/dev/foo7 bs=512 count=1
(See fdisk(8).)
root@ubuntu:~# cat /proc/partitions
major minor #blocks name

 253 0 10485760 vda
 253 1 10484736 vda1
 253 16 10485760 vdb
 253 17 10485759 vdb1
 253 32 366 vdc
  11 0 1048575 sr0

Fixed in https://github.com/canonical/cloud-init/pull/1932

This bug is believed to be fixed in cloud-init in version 23.1. If this is still a problem for you, please make a comment and set the state back to New

Thank you.

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/3490