Comment 0 for bug 1718699

curtin: 0.1.0~bzr505-0ubuntu1~16.04.1

How to (possibly) reproduce:

Let's say you have 3 disks, one as faster, another 2 as slower.

1. create a two partition on the faster one
2. set each partition as bcache cache device and use each slow disk as backing device
   (2 bcache sets in total)
3. install OS using the bcache devices (with MAAS in my case)
4. quick erase all disks (erasing a few megabytes at the beginning and the end of the drives with MAAS in my case)
5. use the same machine again with the same bcache layout, then install OS
6. Get an installation failure with "Device or resource busy"

My gut feeling is that backing devices' bcache signature was deleted by quick erase, but the bcache signature of the second partition of the cache device wasn't cleanup because it was in the middle of the disk (not covered by quick erase). Then, bcache was in unclean state which might cause "Device or resource busy". Possibly more bcache cleanup just before installing OS may be required.

curtin: Installation started. (0.1.0~bzr505-0ubuntu1~16.04.1)
third party drivers not installed or necessary.
Failed to exclusively open path: /dev/nvme0n1p2
Device holders with exclusive access: []
Device mounts: []
Possible users of /dev/nvme0n1p2:
None
Failed to exclusively open path: /dev/nvme0n1p2
Device holders with exclusive access: []
Device mounts: []
Possible users of /dev/nvme0n1p2:
None
Failed to exclusively open path: /dev/nvme0n1p2
Device holders with exclusive access: []
Device mounts: []
Possible users of /dev/nvme0n1p2:
None
Failed to exclusively open path: /dev/nvme0n1p2
Device holders with exclusive access: []
Device mounts: []
Possible users of /dev/nvme0n1p2:
None
[Errno 16] Device or resource busy: '/dev/nvme0n1p2'
curtin: Installation failed with exception: Unexpected error while running command.
Command: ['curtin', 'block-meta', 'custom']
Exit code: 3
Reason: -
Stdout: Failed to exclusively open path: /dev/nvme0n1p2
        Device holders with exclusive access: []
        Device mounts: []
        Possible users of /dev/nvme0n1p2:
        None
        Failed to exclusively open path: /dev/nvme0n1p2
        Device holders with exclusive access: []
        Device mounts: []
        Possible users of /dev/nvme0n1p2:
        None
        Failed to exclusively open path: /dev/nvme0n1p2
        Device holders with exclusive access: []
        Device mounts: []
        Possible users of /dev/nvme0n1p2:
        None
        Failed to exclusively open path: /dev/nvme0n1p2
        Device holders with exclusive access: []
        Device mounts: []
        Possible users of /dev/nvme0n1p2:
        None
        [Errno 16] Device or resource busy: '/dev/nvme0n1p2'

Stderr: ''