kernel update, no dkms update for virtualbox drivers (from ppa)

[Menion]

Hi all
I am running an amd64 Ubuntu xenial host. I have dkms installed and also a running installation of Virtualbox 5.2, taken from virtualbox ppa (no ubuntu repository)
I have updated the kernel to mainline 4.14.15, dkms update have been triggered (ZFS file system modules have been recompiled) but this didn't happen for the virtualbox host kernel drivers ( /misc/vboxdrv.ko /misc/vboxnetflt.ko /misc/vboxnetadp.ko /misc/vboxpci.ko)
So I had to reboot the server in order to run the new kernel and manually run "sudo dpkg-reconfigure virtualbox-5.2"
Is it a normal behaviour for the ppa virtualbox?

[Perryg]

Is it a normal behaviour for the ppa virtualbox?

AFAIK VirtualBox does not have an official ppa. That would be an ubuntu contributor of some kind offering their version. As for the question is a reboot normal? Sometimes. It depends on several things and some being the host OS.

[socratis]

AFAIK VirtualBox does not have an official ppa.

Maybe I'm wrong, but aren't the directions for the "Debian-based Linux distributions" all about adding a VirtualBox ppa?

[Menion]

Well, I have misused the word ppa
I mean the virtualbox official builds for supported distribution, this source:

deb https://download.virtualbox.org/virtualbox/debian xenial contrib

This is different than the canonical package, that for xenial is stuck to 5.0. In the canonical repo, there is a package named "virtualbox-dkms", whereas there is nothing similar in the above repository, where everything (except the addons) seems included in the virtualbox-5.2 package

[Perryg]

AFAIK VirtualBox does not have an official ppa.

Maybe I'm wrong, but aren't the directions for the "Debian-based Linux distributions" all about adding a VirtualBox ppa?

It is for adding an entry to the llist of repositories used by the OS.. "ppa" is specific to ubuntu only, as is virtualbox-dkms, which IIRC is to allow the guest additions to stay in sync and not the host portion, but I could be wrong about that because I don't use it. Kernel updates require standard dkms which is being phased out for what ever reason. All of this systemd crap is causing a headache because Linux was great and they wanted it to be more like windows. Big mistake IMHO.

[Menion]

Why are you mixing dkms with systemd vs sysV (that it is a soooo nonsense fight)?
There is nothing to do with it. Also you are mixing virtualbox-dkms with virtualbox-guest-dkms that are two completely different things
I just wanted to understand if the virtualbox official packages are expected to support dkms or not.
And it is not a windowish thing here. The question is very very meaningful. This because if, as in my case, you are running in virtualbox a router OS which gives to the host itself the normal connectivity, then you just cannot afford to have to reboot to run the new kernel before updating the virtualbox modules, since you will loose the connectivity due to the fact that without the kernel modules, virtualbox cannot start, forcing you to go for the fallback connectivity (that requires physical access to some specific VLAN...)

[Perryg]

Hey I have a right to an opinion too. I was venting about things I don't like and answering a question to socratis ( thus my included quote ). I already answered your question about a reboot. As I said it depends. VirtualBox kernel mode drivers may require a reboot of the host ( more so these days with systemd ). Especially if the kernel has been changed a lot. Even with dkms this may be necessary because the modules were recompiled automatically but that does not mean they can be loaded. That is determined by the host OS. The old init system could and did replace these modules without a reboot a lot more than systemd does. But you know what It only matters to what you believe.

One last bit of advise you can use or not. Never do an upgrade during peak time when services are needed the most. Things can and do go wrong and well...

[Menion]

The old init system could and did replace these modules without a reboot a lot more than systemd does. But you know what It only matters to what you believe.

Sorry but I have lost you here. Kernel modules must be recompiled against the new kernel. Even two different compilation of the very same kernel version, will require a dedicated compilation of the out of tree kernel modules, due to different signature! It is not a matter of loading and not loading (which AFAIK it is not even driven explicitly by any sysV or systemd script). The only place where the recompilation can happen is in a post-install action in the .deb package or via dkms.
So, from your words I understand that the dkms framework is not supported by the virtualbox debs?
Is there any way then to recompile modules against a custom (not the running) kernel?

[Perryg]

The only place where the recompilation can happen is in a post-install action in the .deb package or via dkms.

I am afraid this does not compute. Upgrades often force a recompilation of the VirtualBox KMD's. And do not require the .deb package at all. dkms does force a recompilation when it detects a kernel change. Usually the only thing that you need to do to manually recompile the modules is to run the vboxdrv with the setup flag to achieve this. ( rcvboxdrv setup )
But all of this is still academic because it will still require a reboot to initiate the recompiled modules. You can try to stop and start vboxdrv but it more than likely will not work because the KMDs are loaded at boot and tied to the kernel.

Is there any way then to recompile modules against a custom (not the running) kernel?

Not that I am aware of. You can always build on a different machine with a different kernel, but to what end? You still need to install it on the running machine.

[Menion]

Thanks for the answers
All the drawback you have mentioned, just says that it would very helpful to have virtualbox to support DKMS. Or at least modify vboxdrv so it can manage different kernel than the running one.
I have checked around, DKMS does not seem to be phased out or deprecated