@DennisFaucher

Describe the bug

[Author TODO: A clear and concise description of what the bug is.]
When using the tutorial at https://github.com/firecracker-microvm/firecracker/blob/main/docs/getting-started.md, the rootfs will not mount when booting the VM. Errors on boot are:

[ 0.961380] No filesystem could mount root, tried:
[ 0.961380] ext3
[ 0.962433] ext2
[ 0.962792] ext4
[ 0.963133] squashfs
[ 0.963516] xfs
[ 0.963901]
[ 0.964487] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(254,0)

Is there a better rootfs to use?

To Reproduce

[Author TODO: Steps to reproduce the behaviour:]

Follow the tutorial, boot the VM, rootfs fails to mount

Expected behaviour

[Author TODO: A clear and concise description of what you expected to happen.]
Follow the tutorial, boot the VM, rootfs mounts

Environment

[Author TODO: Please supply the following information):]

• Firecracker version: v1.12.1
• Host and guest kernel versions:
• $ sudo lsb_release -a
  No LSB modules are available.
  Distributor ID: Ubuntu
  Description: Ubuntu 24.04.3 LTS
  Release: 24.04
  Codename: noble

$ uname -a
Linux firecracker-kvm 6.14.0-27-generic #27~24.04.1-Ubuntu SMP PREEMPT_DYNAMIC Tue Jul 22 17:38:49 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

• Rootfs used:

Download a rootfs

wget -O ubuntu-$ubuntu_version.squashfs.upstream "https://s3.amazonaws.com/spec.ccfc.min/$latest_ubuntu_key"

Create an ssh key for the rootfs

unsquashfs ubuntu-$ubuntu_version.squashfs.upstream
ssh-keygen -f id_rsa -N ""
cp -v id_rsa.pub squashfs-root/root/.ssh/authorized_keys
mv -v id_rsa ./ubuntu-$ubuntu_version.id_rsa

create ext4 filesystem image

sudo chown -R root:root squashfs-root
truncate -s 400M ubuntu-$ubuntu_version.ext4
sudo mkfs.ext4 -d squashfs-root -F ubuntu-$ubuntu_version.ext4

• Architecture: x86_64
• Any other relevant software versions:

Additional context

[Author TODO: How has this bug affected you?]

[Author TODO: What are you trying to achieve?]

[Author TODO: Do you have any idea of what the solution might be?]

Checks

• Have you searched the Firecracker Issues database for similar problems?
• Have you read the existing relevant Firecracker documentation?
• Are you certain the bug being reported is a Firecracker issue?