Ubuntu 20.04 Cloud Image: NFS Server won't start

Question

I just installed the Ubuntu 20.04 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

# uname -a
Linux kubix-cnt01 5.4.0-1061-kvm #64-Ubuntu SMP Thu Mar 24 20:55:55 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux

Any idea?

Thx in advance

T0mc@

Answer 1

I can see that you opened a bug on Launchpad: https://bugs.launchpad.net/ubuntu/+source/linux-meta-kvm/+bug/1968612

TL;DR linux-kvm (which is the default kernel installed in minimal cloud-images) does not come with the nfsd.ko module and that breaks nfs-server install.

As a workaround, users can install a different kernel flavor (like linux-generic) or directly choose the full server image on cloud-images.ubuntu.com (ubuntu-20.04-server-cloudimg-amd64.img).