How to force yum not to update certain packages?

How to force yum not to update certain packages, such as kernel?

I manually compiled a kernel module for a specific kernel version. As long as it works well, I do not want to update it. Another example is that I want a specific version of sbt.

How to force yum exclude it from being updated.

For exclude kernel and sbt from being updated by yum, adding this line to /etc/yum.conf:

exclude=sbt kernel