How to troubleshoot vm not starting

[kuba-moo]

I have a custom kernel build, I used to put it into a VM to do my testing, I wanted to cut out the installation steps and give virtme-ng a go. But even tho (I think) I enabled all the config options the prompt never appears. The command just hangs, qemu takes 100% of CPU and I have to kill the process.

Is there an easy way to surface the kernel logs while the vm boots?

[arighi]

Have you tried to use vng -v (verbose mode)? With -v you should see all the boot messages, maybe that can help to figure out what's going on.

You can also try to generate a minimal .config for virtme-ng using vng -b --kconfig, recompile the kernel and see if it boots. If that's the case maybe the reason of the failure is that you're missing a required config option.

[kuba-moo]

I did a vng -b and that works fine. There's some output as things get built, and in the end it plonks me into a shell with the new kernel.

When I try vng -v -r build_mm/vmlinux (where the vmlinux is my custom build) - there's no output, just fans spinning up on my machine :(

[arighi]

@kuba-moo you can't run vmlinux directly, you can either use vng -r arch/x86/boot/bzImage (assuming you're on x86) or simply use vng and it'll figure out the proper boot file automatically (assuming you're in the linux source dir).

[kuba-moo]

bzImage works, thanks a lot!!