kernel command line options (was Re: [vox-tech] problematic computer (when installing linux) [fixed])

[Ken Bloom]

On Wed, Nov 17, 2004 at 01:05:45PM -0800, Jeff Newmiller wrote:
> On Wed, 17 Nov 2004, Rick Moen wrote:
> 
> [discussion of variations on kernel options omitted]
> 
> > Which begs the question:  How does one do that on arbitrary Linux 
> > distributions, if they all implement kernel command-line options 
> > differently?  (Yes, I do know that more-conservative Linux
> > distributions' kernels disable fancy addressing modes for IDE, by
> > default.)
> 
> Well, you could take the top-down approach and try to make or add to a
> standard (LSB?).
> 
> However, when I write a program that accepts commandline options, I have
> to document them, or others won't know which ones are available... the
> problem is really similar.  We usually have standard mechanisms for
> finding these things out, decided by convention.  "--help" is pretty
> common these days, as is "man commandname" or googling.  Due to the nature
> of the kernel boot process, we may not have access to "man" or google,
> though, so Knoppix's approach to self-documenting through boot menus is
> the best option.
> 
> Some combination of the above seems to be the tried-and-true approach.

Kernel parameters are documented all over the kernel documentation,
which can be found in the Documentation directory of a kernel source
tree. They're documented by driver. They're also all listed briefly in
kernel-parameters.txt (in the same directory).

I don't think that distributions have different versions of the
parameters documented in kernel-parameters.txt, unless these changed
dramatically from kernel 2.4 to 2.6, and the distros are using
different versions of the kernel.

A distribution can create its own parameters, however.  When you boot
your system, all of the kernel parameters are stored in /proc/cmdline.
This allows userspace processes to see what parameters were passed,
and behave differently based on what they see. For example, knoppix
takes advantage of this to add a custom option for selecting the
locale and language used when the system boots up.
this, because of the way it is implemented.

Lastly, there also seem to be some undocumented variations on
parameter names in the kernel itself. For example, I always go into
single-user mode with "linux single". kernel-parameters.txt says it
should be "linux S". well, "linux single" still works for me.

--Ken Bloom

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