Symptoms
Backup of a Linux machine with kernel 5.9 or later fails with an error similar to:
The SnapAPI kernel module is not loaded for the kernel 5.12.13-300.fc34.x86_64 that is running in this system. Install the module for this kernel version, and then retry the backup.
Cause
Earlier versions of mainstream kernel did not have interfaces for snapshotting, and SnapAPI module could not use these kernels for snapshotting purposes.