[Bug 2125827] Re: Jammy grub2 failed to detect 2nd virtio disk

Wed Oct 1 08:53:36 UTC 2025

I Can reproduce everything you said above on Ubuntu 24.04 (Noble):

# Prepare images:

uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily arch=amd64 label=daily release=focal
uvt-simplestreams-libvirt --verbose sync --source http://cloud-images.ubuntu.com/daily arch=amd64 label=daily release=jammy

uvt-kvm create --password=ubuntu f arch=amd64 label=daily release=focal
uvt-kvm create --password=ubuntu j arch=amd64 label=daily release=jammy

# Allow to enter the GRUB menu inside the images:
uvt-kvm ssh f
sudo vim /etc/default/grub.d/50-cloudimg-settings.cfg
GRUB_TIMEOUT=10
GRUB_TIMEOUT_STYLE=menu
sudo update-grub

uvt-kvm ssh j
sudo vim /etc/default/grub.d/50-cloudimg-settings.cfg
GRUB_TIMEOUT=10
GRUB_TIMEOUT_STYLE=menu
sudo update-grub

# Create a virtual machine with two disks, both using virtio.

sudo /usr/bin/qemu-system-x86_64 \
  -machine q35,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
  -cpu host \
  -m 2048 \
  -smp 1 \
  -nodefaults \
  -boot strict=on \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/f.qcow","node-name":"libvirt-1-storage"}' \
  -blockdev '{"node-name":"libvirt-1-format","driver":"qcow2","file":"libvirt-1-storage"}' \
  -device virtio-blk-pci,drive=libvirt-1-format,id=virtio-disk0,addr=0x2,bootindex=1 \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/j.qcow","node-name":"libvirt-2-storage"}' \
  -blockdev '{"node-name":"libvirt-2-format","driver":"qcow2","file":"libvirt-2-storage"}' \
  -device virtio-blk-pci,drive=libvirt-2-format,id=virtio-disk1,addr=0x3 \
  -boot menu=on -nographic -serial mon:stdio

# Inside the GRUB menu, hit "c":

                             GNU GRUB  version 2.04

   Minimal BASH-like line editing is supported. For the first word, TAB   
   lists possible command completions. Anywhere else TAB lists possible   
   device or file completions. ESC at any time exits.                     

grub> ls
(hd0) (hd0,gpt15) (hd0,gpt14) (hd0,gpt1)

=> We can only see hd0

# Create a virtual machine with two disks: one using virtio and the
other using SATA.

sudo /usr/bin/qemu-system-x86_64 \
  -machine q35,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
  -cpu host \
  -m 2048 \
  -smp 1 \
  -nodefaults \
  -boot strict=on,menu=on \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/f.qcow","node-name":"libvirt-1-storage"}' \
  -blockdev '{"node-name":"libvirt-1-format","driver":"qcow2","file":"libvirt-1-storage"}' \
  -device virtio-blk-pci,drive=libvirt-1-format,id=virtio-disk0,addr=0x2,bootindex=1 \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/j.qcow","node-name":"libvirt-2-storage"}' \
  -blockdev '{"node-name":"libvirt-2-format","driver":"qcow2","file":"libvirt-2-storage"}' \
  -device ich9-ahci,id=ahci0,bus=pcie.0,addr=0x3 \
  -device ide-hd,drive=libvirt-2-format,id=ide-disk1,bus=ahci0.0 \
  -nographic -serial mon:stdio

# Inside the GRUB menu, hit "c":

                             GNU GRUB  version 2.04

   Minimal BASH-like line editing is supported. For the first word, TAB   
   lists possible command completions. Anywhere else TAB lists possible   
   device or file completions. ESC at any time exits.                     

grub> ls
(hd0) (hd0,gpt15) (hd0,gpt14) (hd0,gpt1) (hd1) (hd1,gpt15) (hd1,gpt14) (hd1,gpt
1)

=> We can see hd0 and hd1!

# Original VM with 2 virtio disks. With "-boot strict=on" but without
",bootindex=1":

sudo /usr/bin/qemu-system-x86_64 \
  -machine q35,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
  -cpu host \
  -m 2048 \
  -smp 1 \
  -nodefaults \
  -boot strict=on \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/f.qcow","node-name":"libvirt-1-storage"}' \
  -blockdev '{"node-name":"libvirt-1-format","driver":"qcow2","file":"libvirt-1-storage"}' \
  -device virtio-blk-pci,drive=libvirt-1-format,id=virtio-disk0,addr=0x2 \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/j.qcow","node-name":"libvirt-2-storage"}' \
  -blockdev '{"node-name":"libvirt-2-format","driver":"qcow2","file":"libvirt-2-storage"}' \
  -device virtio-blk-pci,drive=libvirt-2-format,id=virtio-disk1,addr=0x3 \
  -boot menu=on -nographic -serial mon:stdio

                             GNU GRUB  version 2.04

   Minimal BASH-like line editing is supported. For the first word, TAB   
   lists possible command completions. Anywhere else TAB lists possible   
   device or file completions. ESC at any time exits.                     

grub> ls
(hd0) (hd0,gpt15) (hd0,gpt14) (hd0,gpt1) (hd1) (hd1,gpt15) (hd1,gpt14) (hd1,gpt
1)

=> We can see both disks!

# Original VM with 2 virtio disks. Without "-boot strict=on" but with ",bootindex=1":

sudo /usr/bin/qemu-system-x86_64 \
  -machine q35,accel=kvm,usb=off,vmport=off,dump-guest-core=off \
  -cpu host \
  -m 2048 \
  -smp 1 \
  -nodefaults \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/f.qcow","node-name":"libvirt-1-storage"}' \
  -blockdev '{"node-name":"libvirt-1-format","driver":"qcow2","file":"libvirt-1-storage"}' \
  -device virtio-blk-pci,drive=libvirt-1-format,id=virtio-disk0,addr=0x2,bootindex=1 \
  -blockdev '{"driver":"file","filename":"/var/lib/uvtool/libvirt/images/j.qcow","node-name":"libvirt-2-storage"}' \
  -blockdev '{"node-name":"libvirt-2-format","driver":"qcow2","file":"libvirt-2-storage"}' \
  -device virtio-blk-pci,drive=libvirt-2-format,id=virtio-disk1,addr=0x3 \
  -boot menu=on -nographic -serial mon:stdio

                             GNU GRUB  version 2.04

   Minimal BASH-like line editing is supported. For the first word, TAB   
   lists possible command completions. Anywhere else TAB lists possible   
   device or file completions. ESC at any time exits.                     

grub> ls
(hd0) (hd0,gpt15) (hd0,gpt14) (hd0,gpt1) (hd1) (hd1,gpt15) (hd1,gpt14) (hd1,gpt
1)

=> We can see both disks.

When swapping the f.qcow and j.qcow images to have the primary image be
Jammy, using GRUB 2.06 I can confirm the very same behavior, so I think
this is unrelated to GRUB.

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https://bugs.launchpad.net/bugs/2125827

Title:
  Jammy grub2 failed to detect 2nd virtio disk

Status in grub2 package in Ubuntu:
  Invalid
Status in qemu package in Ubuntu:
  New

Bug description:
  I am using qemu-system-x86_64 on Jammy to create a VM with two disks, both on the virtio bus.
  When I enter the GRUB shell and use the "ls" command, only the first virtio disk is listed.
  However, if I change the second disk to the SATA bus, GRUB can recognize the second disk.

  Steps and result

  Jammy: https://paste.ubuntu.com/p/TXjzbcXG5z/

  This issue cannot be reproduced on Focal.

  Focal: https://paste.ubuntu.com/p/MF2NKfsTSt/

  The impact of this is that chainloading will fail.

  /etc/grub.d/25_custom

  menuentry "Attached-IDE-Disk" {
  set root=(hd1)
  insmod linux
  insmod chain
  chainloader +1
  }

  I'm not sure whether this is an issue with QEMU or GRUB. Thus, I filed
  a bug on grub2 as well.
  https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/2125826

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