How to load kernel modules by default?

[DjVinnii]

I deployed Rook instead of Longhorn as a storage operator in my cluster. I noticed some pods are in a CrashLoopBackOff state. After some investigation I found out this is caused by some pods that are trying to enable the rbd kernel module. Apparently the root cause is the mismatch of the modprobe version on the host versus the container. The newer version on the host ships zstd-compressed kernel modules, but the container itself does not support that.

As a workaround I would like to enable the kernel module by default (on boot) on the agents until the compressed formatted is supported in the upstream container images. Is there a recommended way to achieve this?

Host:

# grep PRETTY /etc/os-release
PRETTY_NAME="openSUSE MicroOS"
# modprobe --version
kmod version 31
+ZSTD +XZ +ZLIB +LIBCRYPTO -EXPERIMENTAL

Container:

# grep PRETTY /etc/os-release
PRETTY_NAME="CentOS Stream 8"
# modprobe --version
kmod version 25
+XZ +ZLIB +OPENSSL -EXPERIMENTAL

[pat-s]

The following worked for me:

echo -e "rbd\nnbd" > /etc/modules-load.d/custom.conf

Reboot afterward, and modules are loaded by default on the host. This lets the rbd and nbd pods succeed.