Ability to pass kernel command line

[nakamorichi]

Is your feature request related to a problem? Please describe.
Not exactly problem, but currently it's somewhat inconvenient to customize vm's kernel command line.

Describe the solution you'd like
Would like to have e.g. configuration option for overriding and/or appending to kernel command line.

Describe alternatives you've considered
cloud init apparently has a way for setting kernel command line, but also their approach is a bit hacky: https://cloudinit.readthedocs.io/en/latest/explanation/kernel-command-line.html

It might be also possible to utilize kvm_arguments by passing something like kvm_arguments = "-append <...>" (qemu-kvm man), but I wasn't able to get it work.

Additional context
In order to fine-tune vm, want to be able to modify kernel command line. Currently I'm using cloud-init, and am modifying the command line during vm creation as part of cloud init, but this feels too hacky and would like instead to be able to pass it directly via configuration instead of modifying already running vm.

[bpg]

Hey @nakamorichi 👋🏼

It might be also possible to utilize kvm_arguments by passing something like kvm_arguments = "-append <...>" (qemu-kvm man), but I wasn't able to get it work.

I think kvm_arguments should help in your use case, tho I haven't use it myself.

It sets the args VM config option:

And example usage from the forums: https://forum.proxmox.com/threads/passing-kernel-parameters.135802/#post-601466

What exactly didn't work for you?

Speaking about the "enhancement" aspect of this ticket, I don't thinks we have any other options besides kvm or cloud-init arguments. The provider is limited to what mechanisms PVE supports for the VM management. My preference is to stick to the PVE API and limit other "magical" stuff (i.e. direct file manipulations or calling CLI tools over SSH) to the minimum, as it is really hard to maintain in long term.

[nakamorichi]

@bpg -kernel (required for -append) seems to refer to local file system, not the VM's, so that approach doesn't seem to work.

In case qemu/kvm doesn't support such functionality, I guess it's not possible to implement on the provider side either..? I wonder what would be the right place for such feature request: qemu, kvm, proxmox, or cloud-init team?

[bpg]

Hmm... I'm confused... Let's step back for a moment. 😅

What is the actual problem you're trying to solve? Is there a specific VM image that you're trying to boot in unusual way?