Ubuntu 20.04 Cloud Image: missing nfsd.ko module in linux-kvm

[T0mCat]

I just installed the Ubuntu 20.04 LTS minimal cloud image (from here: https://cloud-images.ubuntu.com/minimal/releases/focal/release/) in a Proxmox VM. Then I installed the NFS Server with

apt install nfs-server

But it fails to start with these errors in journalctl:

Apr 10 18:03:55 servername01 systemd[1]: Starting Preprocess NFS configuration...
-- Subject: A start job for unit nfs-config.service has begun execution
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- A start job for unit nfs-config.service has begun execution.
--
-- The job identifier is 563.
Apr 10 18:03:55 servername01 mount[9668]: mount: /proc/fs/nfsd: unknown filesystem type 'nfsd'.
Apr 10 18:03:55 servername01 systemd[1]: proc-fs-nfsd.mount: Mount process exited, code=exited, status=32/n/a
-- Subject: Unit process exited
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- An n/a= process belonging to unit proc-fs-nfsd.mount has exited.
--
-- The process' exit code is 'exited' and its exit status is 32.
Apr 10 18:03:55 servername01 systemd[1]: proc-fs-nfsd.mount: Failed with result 'exit-code'.
-- Subject: Unit failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- The unit proc-fs-nfsd.mount has entered the 'failed' state with result 'exit-code'.
Apr 10 18:03:55 servername01 systemd[1]: Failed to mount NFSD configuration filesystem.
-- Subject: A start job for unit proc-fs-nfsd.mount has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- A start job for unit proc-fs-nfsd.mount has finished with a failure.
--
-- The job identifier is 556 and the job result is failed.
Apr 10 18:03:55 servername01 systemd[1]: Dependency failed for NFS Mount Daemon.

"mount: /proc/fs/nfsd: unknown filesystem type 'nfsd'." ... So it seems, that the nfsd kernel module is missing:

# modprobe nfsd
modprobe: FATAL: Module nfsd not found in directory /lib/modules/5.4.0-1061-kvm

I can't figure out how to install this for the running kernel.

Any idea?

[Andreas Hasenack (ahasenack)]

I see you are running the kvm kernel flavor, and indeed I don't see the nfsd.ko module, nor a package named like linux-modules-extra-kvm, which, in the case of the other cloud kernels, does have nfsd.ko.

I'm changing this bug to be about the linux kernel, as they can answer best why nfsd.ko is not present, and in the meantime I suggest you install another kernel flavor, like perhaps linux-image-virtual.

[Éric St-Jean (esj)]

indeed, this image has a minimal kernel
you can either install the generic kernel, or use the full ubuntu server image which contains the generic kernel, which will have the necessary support

[Éric St-Jean (esj)]

closing this but please feel free to comment if you have additional questions or concerns

[Steve Langasek (vorlon)]

I question whether it's correct to dismiss this as invalid on the basis that this is a minimal image. In general, my expectation is that the minimal image is a suitable base for deploying any of the software in Ubuntu, it's just a smaller starting point.

And the purpose of having a separate KVM kernel flavor is to provide the best kernel for booting in VMs, excluding hardware-specific drivers that are necessarily irrelevant when running on a reasonably-configured VM.

It does not obviously follow from either of these points that the nfsd driver should be excluded from the KVM kernel. It's as reasonable to run an nfs server in a VM as it is anywhere else. And installing the nfs-server package in a minimal VM shouldn't fail with obscure errors.

[Éric St-Jean (esj)]

steve - that's a fair point
pinging kernel

[T0mCat (t0mc)]

@Andreas:
I also had this thought but before changing the kernel flavour I wanted to be sure not to have missed sth. obvious :)

@Seve:
I completely agree with your opinion. Even if this is a minimal image (as a small starting point) it shouldn't prevent installing such common additional server software as NFS Server is IMHO.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Sergiu Bivol (sergiu-bivol)]

I will add that one of the reasons for using a VM in LXD instead of containers is the need for kernel-level stuff like NFS.
Installing the generic kernel pulls in 1.4 GB of dependencies on a VM that currently has 1.4 GB used in total with the kvm kernel