Bug 2355323

Summary: parted detects "broken" GPT on MD member disks with 1.0 MD metadata
Product: [Fedora] Fedora Reporter: Vojtech Trefny <vtrefny>
Component: partedAssignee: Brian Lane <bcl>
Status: CLOSED NOTABUG QA Contact: Fedora Extras Quality Assurance <extras-qa>
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Version: rawhideCC: bcl, kkoukiou
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Last Closed: 2025-04-08 12:32:25 UTC Type: Bug
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Description Vojtech Trefny 2025-03-27 13:41:41 UTC 
Description of problem:

On MD arrays with metadata version 1.0 (with MD metadata at the end of the device) parted detects the GPT partition table on the underlying disks and when using parted users are prompted to fix the GPT destroying the RAID metadata in the process.

This is especially a problem when running installer on such system, because during installation we let parted automatically fix all fixable issues. 


Steps to Reproduce:
1. Create MD RAID with metadata version 1.0 on directly on top of disks: 
   sudo mdadm --create gpttest --run --level=1 --raid-devices=2 --metadata=1.0 /dev/vda /dev/vdb
2. Create GPT on the array
3. Run parted -l

Actual results:

parted shows a warning about the secondary GPT not being at the end of the disk and offers to fix it

Warning: Not all of the space available to /dev/vda appears to be used, you can
fix the GPT to use all of the space (an extra 32 blocks) or continue with the
current setting? 

Expected results:

parted doesn't detect GPT on vda, only on the MD array.
Comment 1 Brian Lane 2025-03-28 16:25:39 UTC 
My initial thought on this is that it's working like it is supposed to, and that the installer is going to need to change how it uses parted when it knows that it has a MD RAID setup. eg. turn off automatic fixing.

Also, why haven't we run into this before? Something must have changed, do you know what? I know that in the past I've experimented with using mdraid and UEFI and didn't hit this. But that has also been quite a while ago.
Comment 2 Vojtech Trefny 2025-03-31 12:40:22 UTC 
This gets more complicated every time I try to reproduce the original issue. But it looks like these steps are not steps to reproduce the original installer issue -- `parted -l` offers to fix GPT on the RAID member disks, but that doesn't happen with just blivet, we don't detect GPT on the disks and parted doesn't offer to fix it with blivet. So the installer error seems to be triggered by something else.

But the system is still very confused in this situation thinking the partition table (and the partitions) are both on the disk and the array:

```
$ lsblk /dev/vda
NAME        MAJ:MIN RM SIZE RO TYPE  MOUNTPOINTS
vda         252:0    0  20G  0 disk  
├─md127       9:127  0  20G  0 raid1 
│ └─md127p1 259:1    0   1G  0 part  
└─vda1      252:1    0   1G  0 part  

$ sudo wipefs /dev/vda
DEVICE OFFSET      TYPE              UUID                                 LABEL
vda    0x4ffffe000 linux_raid_member 52af8b57-57aa-bc58-81f2-16dced9ed8c2 fedora:gpttest
vda    0x1000      gpt                                                    
vda    0x1fe       PMBR    
                                               
$ sudo wipefs /dev/md127
DEVICE OFFSET      TYPE UUID LABEL
md127  0x1000      gpt       
md127  0x4fffdf000 gpt       
md127  0x1fe       PMBR 
```

I'll continue playing with this to see if I am able to reproduce the original installer issue, but even with this setup I'd consider the `parted -l` to be if not a bug than a potentially dangerous behaviour. I think it might be a good idea to change `parted -l` behaviour to show just the warning without the fix/ignore prompt and only offering to fix the partition table when user explicitly runs `parted /dev/vda`.
Comment 3 Brian Lane 2025-03-31 15:20:49 UTC 
No, parted is working just fine, and the prompt is there for good reason. The problem is that this setup mixes partitioning and mdraid. I know you can't avoid doing that if you want it to boot from it, but this also isn't a new situation.