Reducing the need to compile a custom kernel

Panagiotis Christias p.christias at
Fri Feb 10 15:56:58 UTC 2012

On 10/2/2012 15:56, Alexander Leidinger wrote:
> Hi,
> during some big discussions in the last monts on various lists, one of
> the problems was that some people would like to use freebsd-update but
> can't as they are using a custom kernel. With all the kernel modules we
> provide, the need for a custom kernel should be small, but on the other
> hand, we do not provide a small kernel-skeleton where you can load just
> the modules you need.
> This should be easy to change. As a first step I took the generic kernel
> and removed all devices which are available as modules, e.g. the USB
> section consists now only of the USB_DEBUG option (so that the module is
> build like with the current generic kernel). I also removed some storage
> drivers which are not available as a module. The rationale is, that I
> can not remove CAM from the kernel config if I let those drivers inside
> (if those drivers are important enough, someone will probably fix the
> problem and add the missing pieces to generate a module).
> Such a kernel would cover situations where people compile their own
> kernel because they want to get rid of some unused kernel code (and
> maybe even need the memory this frees up).
> The question is, is this enough? Or asked differently, why are you
> compiling a custom kernel in a production environment (so I rule out
> debug options which are not enabled in GENERIC)? Are there options which
> you add which you can not add as a module (SW_WATCHDOG comes to my
> mind)? If yes, which ones and how important are they for you?


we are currently using on every server (in order to maintain a single 
custom kernel) the following options:


Soon, we will also add:


Finally, once we upgrade our jail setup VIMAGE will be also a must.


Panagiotis J. Christias    Network Management Center
p.christias at    National Technical Univ. of Athens, GREECE

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