How to fix 'quotaon: Quota format not supported in kernel' on Linux
I was building a new system for hosting, and that system is a virtualised system with Ubuntu. The OS was built by the provider. After installing everything, I wanted to activate the quota on the filesystem.
The quota check failed with the following message:
quotaon: Quota format not supported in kernel
After a quick check, I noticed that the system was delivered with a "linux-image-virtual" kernel. That kernel does not include the mod_quotav2 modules, and therefore the quota did not work. The solution is to install the package "linux-image-extra-virtual", and that's it.
# apt-get install linux-image-extra-virtual
That package includes the package "linux-modules-extra-5.4.0-91-generic", which includes the quota kernel modules.