Minimal image boot output goes to a non-default console in standard QEMU invocation

[Michał Sawicz]

When booting the xenial or bionic minimal images using qemu, their output goes to the serial console. A default invocation of qemu will not display the serial console output to the user, so it appears that boot has hung.

(This can be verified by pressing Ctrl-Alt-3 in the qemu console, which will display the serial console output.)

[Original Report]

The xenial minimal image [1] as well as the bionic one [2] fail to boot in QEMU/KVM:

$ qemu-system-x86_64 --enable-kvm -hda ubuntu-16.04-minimal-cloudimg-amd64-disk1.img

Results in:
> Booting from Hard Disk...
> error: no such device: root.

$ qemu-system-x86_64 --enable-kvm -hda ubuntu-18.04-minimal-cloudimg-amd64.img

Hangs at:
> Booting from Hard Disk...

[1] http://cloud-images.ubuntu.com/minimal/releases/xenial/release/ubuntu-16.04-minimal-cloudimg-amd64-disk1.img
[2] http://cloud-images.ubuntu.com/minimal/releases/bionic/release/ubuntu-18.04-minimal-cloudimg-amd64.img

[Dan Watkins (oddbloke)]

Hey Saviq,

The output you're seeing is actually a little misleading; the image _is_ booting, but all of its output goes to the serial console. You can see this by pressing Ctrl-Alt-3 in the QEMU console.

(As a side note, you'll also want to add `-net nic,model=virtio` to your invocations to get working networking; qemu defaults to emulating a physical e1000 device, which the KVM-only linux-kvm kernel doesn't have support for.)

I'm going to change this bug to be about the default QEMU console output being misleading and drop its priority.

Thanks,

Dan

[Michał Sawicz (saviq)]

FWIW the grub config has "console=tty1" instead of "console=tty0" - changing that gives me GRUB at least on the default console.

[Michał Sawicz (saviq)]

Just realized CONFIG_VT is disabled in the minimal kernel, so we won't get far with Mir on it :/

[Michał Sawicz (saviq)]

This seems to have bit me again on Hyper-V, I can't see any output from the VM and it never seems to complete booting (which might be due to missing virtualized hardware support, TBD).