revisiting tunables under Safe Mode menu option

[Devin Teske]

> -----Original Message-----
> From: Julian Elischer [mailto:julian at freebsd.org]
> Sent: Thursday, March 01, 2012 1:28 PM
> To: Scott Long
> Cc: Devin Teske; freebsd-current at freebsd.org; 'Devin Teske'; 'John Baldwin';
> 'Andriy Gapon'
> Subject: Re: revisiting tunables under Safe Mode menu option
> 
> On 3/1/12 9:13 AM, Scott Long wrote:
> >
> > 1.  There are a number of knobs that can be manipulated to help enable a
non-
> booting system boot, which in turn gives a system administrator a fighting
chance
> to figure out what's wrong.  ACPI is (or was) one of these options, but there
are
> several others, and up until your re-write of the menu system, they were
opaque
> to the user.  I'd like to explore the idea of having a sub-menu that exposes
these
> knobs and allows them to be individually controlled, but still have an
upper-level
> option that turns them all-on or all-off for ease of use.
> >
> > 2.  There are a ton of kenv/TUNABLE knobs in any given kernel, and many of
> them are useful for sysadmins, even beyond just the 'safe mode' subset.  I'd
like
> to see a post-processor run on the kernel build that collects all of the kenv
knobs
> in that kernel and puts them into a file that can be read by the boot menu
> system.  The system then dynamically turns these into another sub-menu of
> knobs that can be manipulated.
> >
> > So, how hard would it be to have nested sub-menus?  Would (1) be something
> feasible to do in the near term?  Would (2) be feasible to do in the long
term?
> 
> not only collecting stuff from am kernel build but from a running system.
> it would be nice fro example to be able to influence the /etc/rc.d
> system by disabling some functions.
> e.g. come up but don't turn on the window system, or networking..
> We can disable a device but how about specifying a different default
> route than that in /etc/rc.conf?
> 
> if we extract the setup tha tthe machine eventually comes up to, we
> can allow that to be tuned as well.

I'm interested in which path you would choose amongst what I've seen mentioned
thus far:

a. Modifying the boot menu to offer fine-grain control over each aspect of Safe
Mode (wherein perhaps the Safe Mode option becomes a hook for a sub-menu rather
than its current setup as an "On"/"Off" toggle).

b. Keeping Safe Mode as an On/Off toggle, but shifting the fine-grain control to
userland (wherein loader(8) simply sets a safemode Boolean and the user is
dropped into something like single-user mode but with prompts for each feature)

c. Something else.
-- 
Devin


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