Comment 1 for bug 1324200

in 5.0 we added a field on the settings page to change the kernel options for the entire cluster so that they may be able to best suite your needs. This value can only apply after the bootstrap is complete, so may not be a good option for you.

Can you validate if you can change the setting from the cobbler web ui? https://<fuel node>/cobbler_web (cobbler:cobbler)