curtin make_dname doesn't handle non-zero blkid return code

[Andres Rodriguez]

MAAS install log:

W: mdadm: /etc/mdadm/mdadm.conf defines no arrays.
Processing triggers for ureadahead (0.100.0-16) ...
Processing triggers for ufw (0.34~rc-0ubuntu2) ...
mdadm: No arrays found in config file or automatically
An error occured handling 'vda': ProcessExecutionError - Unexpected error while running command.
Command: ['blkid', '-o', 'export', '/dev/vda']
Exit code: 2
Reason: -
Stdout: ''
Stderr: ''
Unexpected error while running command.
Command: ['blkid', '-o', 'export', '/dev/vda']
Exit code: 2
Reason: -
Stdout: ''
Stderr: ''
Installation failed with exception: Unexpected error while running command.
Command: ['curtin', 'block-meta', 'custom']
Exit code: 3
Reason: -

Looking at it:

ubuntu@node01:/curtin/configs$ sudo blkid -o export /dev/vda || echo $?
2

ubuntu@node01:/curtin/configs$ sudo mkfs /dev/vda
mke2fs 1.42.9 (4-Feb-2014)
[...]

ubuntu@node01:/curtin/configs$ sudo blkid -o export /dev/vda && echo $?
UUID=7ccf0859-0e94-427c-940f-b28cb6137e34
TYPE=ext2
0

ubuntu@node01:/curtin/configs$ sudo wipefs -a /dev/vda
2 bytes were erased at offset 0x438 (ext2)
they were: 53 ef

ubuntu@node01:/curtin/configs$ sudo blkid -o export /dev/vda && echo $?

ubuntu@node01:/curtin/configs$ sudo blkid -o export /dev/vda || echo $?
2

[Ryan Harper (raharper)]

I can reproduce this in a trusty 14.04.03 cloudimg, and a spare, empty disk in the VM.

The relevant curtin code is triggered from the passed storage config:

partitioning_commands:
  builtin: [curtin, block-meta, custom]
storage:
  config:
  - {grub_device: true, id: vda, name: vda, path: /dev/vda, ptable: msdos, type: disk,
    wipe: superblock}
  - {id: vdb, name: vdb, path: /dev/vdb, type: disk, wipe: superblock}
  - {device: vda, id: vda-part1, name: vda-part1, number: 1, offset: 2097152B, size: 17176723456B,
    type: partition, uuid: d9a3d0e8-1a4c-4b62-a666-286902f7ffd8, wipe: superblock}
  - {fstype: ext4, id: vda-part1_format, label: root, type: format, uuid: 22c010b5-bcfd-40cc-9f96-cefa1bcf7c64,
    volume: vda-part1}
  - {device: vda-part1_format, id: vda-part1_mount, path: /, type: mount}
  version: 1

The 'name' field here triggered the creation of /dev/disk/by-name/vdb -> /dev/vdb

The make_dname code invokes blkid -o export /dev/vdb , which doesn't *yet* have a filesystem on it, nor a PARTUUID that might be present in a GPT partition table.

The fix for handling the non-zero exit is a trivial fix. More thought needs to go into hanlding how to setup a udev rule for by-name for disks without a PARTUUID.

[Ryan Harper (raharper)]

As a workaround, avoiding passing in the 'name' key in the disk or partition dict will prevent curtin from attempting to generate a dname for that entry.

[Scott Moser (smoser)]

This bug is believed to be fixed in curtin in 17.1. If this is still a problem for you, please make a comment and set the state back to New

Thank you.