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The original question was :
How to prevent a specific kernel from being removed on Oracle Linux 7.9 ?
I just updated my current kernel (5.4.17-2011.6.2.el7uek.x86_64) to a newer version (5.4.17-2036.103.3.1.el7uek.x86_64) and the new kernel did not detect my network card.
I rebooted with the old one and the network card is detected again.
Question : How can I prevent Oracle linux from removing a specific kernel ( in this example 5.4.17-2011.6.2.el7uek.x86_64 ) ? I already raised installonly_limit = 5 and have a backup of / so I can always restore it. I will verify the number of kernel at each update so it won't go beyond 5 . I just like to have an extra precaution so I don't have to restore in case I forget to verify the number of kernels.
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Once I got the answer to my kernel issue I decided to change the question title so it would be more usefull to users ( than the original title )