Bug 2357959

Summary:	kdump fails to generates initrd with default config
Product:	[Fedora] Fedora	Reporter:	Marius Vollmer <mvollmer>
Component:	kdump-utils	Assignee:	Lichen Liu <lichliu>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	unspecified
Version:	42	CC:	coxu, lichliu, mpitt
Target Milestone:	---	Keywords:	Regression
Target Release:	---	Flags:	lichliu: mirror+
Hardware:	x86_64
OS:	Linux
Whiteboard:	CockpitTest
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Marius Vollmer 2025-04-07 15:32:33 UTC

kdump-utils 1.0.52-2.fc42.x86_64
dracut 105-2.fc42.x86_64

This is related to bug 2306035.

The recent upgrade of dracut 103-3.fc42 to 105-2.fc42 in our CI images has broken kdump initrd generation with the default config when /var is on btrfs.

Kdump itself didn't change, but it uses shell functions from dracut, which did change. Specifically, when /var is on btrfs, mkdumprd ends up calling get_persistent_dev from /usr/lib/dracut/dracut-functions.sh with a empty string.

Older versions of get_persistent_dev would not fail when given the empty string. They would just return a bogus result, resulting in a initrd that wouldn't work (see bug 2306035). The newer versions will now fail.

The result is the following unhelpful output from kdumpctl:

    # kdumpctl rebuild
    kdump: Rebuilding /boot/initramfs-6.14.0-63.fc42.x86_64kdump.img
    kdump: mkdumprd: failed to make kdump initrd



Reproducible: Always

Comment 1 Martin Pitt 2025-04-14 06:09:53 UTC

I just spent an hour investigating this in https://github.com/linux-system-roles/kdump/pull/233#issuecomment-2800567079 . This is hilariously hard to debug. Even

    KDUMP_STDLOGLVL=3 KDUMP_SYSLOGLVL=3 KDUMP_KMSGLOGLVL=3 sh -x kdumpctl start

doesn't give something useful. Calling 

  /sbin/mkdumprd -f /boot/initramfs-6.14.0-63.fc42.x86_64kdump.img 6.14.0-63.fc42.x86_64

fails completely silently, and running that with `sh -x` is inscrutable. Thanks Marius for investigating!

Comment 2 Lichen Liu 2025-04-14 06:49:22 UTC

(In reply to Martin Pitt from comment #1)
> I just spent an hour investigating this in
> https://github.com/linux-system-roles/kdump/pull/233#issuecomment-2800567079
> . This is hilariously hard to debug. Even
> 
>     KDUMP_STDLOGLVL=3 KDUMP_SYSLOGLVL=3 KDUMP_KMSGLOGLVL=3 sh -x kdumpctl
> start
> 
> doesn't give something useful. Calling 
> 
>   /sbin/mkdumprd -f /boot/initramfs-6.14.0-63.fc42.x86_64kdump.img
> 6.14.0-63.fc42.x86_64
> 
> fails completely silently, and running that with `sh -x` is inscrutable.
> Thanks Marius for investigating!

Hi Martin,
Debugging with `debug=1 kdumpctl rebuild`, I think this issue happens because kdump does not support btrfs subvol now.

Comment 3 Marius Vollmer 2025-04-14 17:23:33 UTC

(In reply to Lichen Liu from comment #2)
> I think this issue happens because kdump does not support btrfs subvol now.

If you don't want to support it, please make it fail with a clear error message. Don't send people on wild goose chases, please.

Comment 4 Lichen Liu 2025-04-15 12:17:33 UTC

(In reply to Marius Vollmer from comment #3)
> (In reply to Lichen Liu from comment #2)
> > I think this issue happens because kdump does not support btrfs subvol now.
> 
> If you don't want to support it, please make it fail with a clear error
> message. Don't send people on wild goose chases, please.

OK, I think we can keep this bug for improving the error messages.
For btrfs support, I don't have a plan to support it now, but I have added it to the future feature list.

Comment 5 Lichen Liu 2025-11-24 08:06:05 UTC

(In reply to Marius Vollmer from comment #3)
> (In reply to Lichen Liu from comment #2)
> > I think this issue happens because kdump does not support btrfs subvol now.
> 
> If you don't want to support it, please make it fail with a clear error
> message. Don't send people on wild goose chases, please.

Hi Marius, we added basic btrfs support in kdump-uitls 1.0.59, it works on Fedora SilverBlue with the default configuration, can you help to test this issue?

Thanks,
Lichen

Comment 6 Lichen Liu 2025-11-24 08:08:42 UTC

*** Bug 2306035 has been marked as a duplicate of this bug. ***