Inconsistent device numbers after reboot

Inconsistent device numbers after reboot

[Chris Schanzle]

The device ID of my partition containing my home directory changes (sometimes) when I reboot, typically after kernel updates. Sometimes subsequent reboots with the same kernel change it again, but typically after that it is usually consistent.

Changing device ID's causes havoc with tar incremental backups - tar consider all files are new.

Is there something I can change to keep st_dev static?

I'm running Fedora 33 with my home filesystem as XFS on a LVM supported by md RAID1.

I'm not sure if this is caused by LVM or md or something else, hence I ask the experts here.

I have a cron job logging the device ID of my home directory at boot with the kernel version, included below.

Any thoughts would be appreciated!  Thanks in advance.

2021-02-20 22:47 fd03h/64771d 5.10.16-200.fc33.x86_64
2021-02-25 12:59 fd03h/64771d 5.10.17-200.fc33.x86_64
2021-02-27 22:49 fd03h/64771d 5.10.18-200.fc33.x86_64
2021-03-03 12:11 fd04h/64772d 5.10.19-200.fc33.x86_64
2021-03-12 16:25 fd03h/64771d 5.10.21-200.fc33.x86_64
2021-03-16 22:55 fd06h/64774d 5.10.22-200.fc33.x86_64
2021-03-19 14:00 fd06h/64774d 5.10.23-200.fc33.x86_64
2021-03-23 09:35 fd06h/64774d 5.11.7-200.fc33.x86_64
2021-03-28 11:24 fd04h/64772d 5.11.10-200.fc33.x86_64
2021-03-30 17:26 fd06h/64774d 5.11.10-200.fc33.x86_64
2021-04-02 20:11 fd03h/64771d 5.11.11-200.fc33.x86_64
2021-04-14 17:41 fd06h/64774d 5.11.12-200.fc33.x86_64
2021-04-16 17:37 fd06h/64774d 5.11.13-200.fc33.x86_64
2021-04-18 11:58 fd03h/64771d 5.11.14-200.fc33.x86_64
2021-04-22 01:34 fd03h/64771d 5.11.15-200.fc33.x86_64
2021-04-22 01:41 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:42 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:43 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:44 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:45 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:46 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-22 01:47 fd06h/64774d 5.11.15-200.fc33.x86_64
2021-04-27 15:18 fd03h/64771d 5.11.16-200.fc33.x86_64
2021-04-28 21:10 fd03h/64771d 5.11.16-200.fc33.x86_64
2021-04-28 21:11 fd06h/64774d 5.11.16-200.fc33.x86_64
2021-04-28 21:12 fd06h/64774d 5.11.16-200.fc33.x86_64
2021-04-28 21:13 fd06h/64774d 5.11.16-200.fc33.x86_64
2021-04-28 21:14 fd06h/64774d 5.11.16-200.fc33.x86_64
2021-05-03 19:23 fd03h/64771d 5.11.17-200.fc33.x86_64
2021-05-08 10:43 fd03h/64771d 5.11.17-200.fc33.x86_64
2021-05-08 10:44 fd06h/64774d 5.11.17-200.fc33.x86_64
2021-05-08 10:45 fd06h/64774d 5.11.17-200.fc33.x86_64
2021-05-08 10:46 fd06h/64774d 5.11.17-200.fc33.x86_64
2021-05-08 10:46 fd06h/64774d 5.11.17-200.fc33.x86_64
2021-05-08 10:48 fd06h/64774d 5.11.17-200.fc33.x86_64
2021-05-11 01:28 fd06h/64774d 5.11.18-200.fc33.x86_64
2021-05-14 22:51 fd03h/64771d 5.11.19-200.fc33.x86_64
2021-05-16 12:52 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-16 12:53 fd05h/64773d 5.11.20-200.fc33.x86_64
2021-05-16 12:54 fd04h/64772d 5.11.20-200.fc33.x86_64
2021-05-16 12:55 fd06h/64774d 5.11.20-200.fc33.x86_64
2021-05-16 12:56 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-16 12:57 fd05h/64773d 5.11.20-200.fc33.x86_64
2021-05-16 12:58 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-16 12:58 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-16 12:59 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-16 13:01 fd03h/64771d 5.11.20-200.fc33.x86_64
2021-05-20 23:14 fd03h/64771d 5.11.21-200.fc33.x86_64
2021-05-30 22:16 fd06h/64774d 5.11.21-200.fc33.x86_64
2021-06-03 22:19 fd03h/64771d 5.11.21-200.fc33.x86_64
2021-06-03 22:36 fd06h/64774d 5.11.21-200.fc33.x86_64
2021-06-05 14:00 fd03h/64771d 5.11.21-200.fc33.x86_64
2021-06-20 22:32 fd03h/64771d 5.11.21-200.fc33.x86_64
2021-07-05 18:47 fd03h/64771d 5.11.21-200.fc33.x86_64
2021-07-28 17:53 fd03h/64771d 5.13.4-100.fc33.x86_64
2021-08-02 16:05 fd03h/64771d 5.13.4-100.fc33.x86_64
2021-08-02 16:30 fd03h/64771d 5.13.4-100.fc33.x86_64
2021-08-10 08:31 fd06h/64774d 5.13.8-100.fc33.x86_64
2021-08-18 21:13 fd03h/64771d 5.13.10-100.fc33.x86_64
2021-08-22 00:17 fd03h/64771d 5.13.12-100.fc33.x86_64
2021-09-16 07:04 fd06h/64774d 5.13.12-100.fc33.x86_64
2021-09-16 07:27 fd06h/64774d 5.13.15-100.fc33.x86_64
2021-09-25 12:41 fd03h/64771d 5.13.16-100.fc33.x86_64
2021-10-06 14:34 fd06h/64774d 5.14.9-100.fc33.x86_64
2021-10-06 14:35 fd06h/64774d 5.14.9-100.fc33.x86_64
2021-10-06 14:37 fd06h/64774d 5.14.9-100.fc33.x86_64
2021-10-16 10:59 fd06h/64774d 5.14.11-100.fc33.x86_64
2021-10-19 14:54 fd03h/64771d 5.14.12-100.fc33.x86_64
2021-10-19 14:57 fd03h/64771d 5.14.12-100.fc33.x86_64
2021-10-19 15:00 fd03h/64771d 5.14.12-100.fc33.x86_64
2021-10-19 15:02 fd03h/64771d 5.14.12-100.fc33.x86_64
2021-10-22 11:44 fd03h/64771d 5.14.12-100.fc33.x86_64

Re: Inconsistent device numbers after reboot

[Peter Grandi]

> The device ID of my partition containing my home directory
> changes (sometimes) when I reboot

This is an intrinsic behaviour of the Linux kernel, and it is
futile to fight it (it also depends on enumeration order). Note
that is the id of the special device file which has no intrinsic
significance, unlike that disk id in the label, or the partition
id (for GPT), or the filesystem id (for most filesystems), so
using it to uniquely identify archived files is "dubious".

> Changing device ID's causes havoc with tar incremental backups
> - tar consider all files are new.

For that reason there is a specific option in recent versions of
GNU 'tar':

       "--no-check-device
              Do not check device numbers when creating incremental archives."

Re: Inconsistent device numbers after reboot

[Chris Schanzle]

On 10/23/21 15:18, Peter Grandi wrote:
>> The device ID of my partition containing my home directory
>> changes (sometimes) when I reboot
> This is an intrinsic behaviour of the Linux kernel, and it is
> futile to fight it
>
>> Changing device ID's causes havoc with tar incremental backups
>> - tar consider all files are new.
> For that reason there is a specific option in recent versions of
> GNU 'tar':
>
>         "--no-check-device
>                Do not check device numbers when creating incremental archives."

Excellent, was not aware of that option. Thank you!