Active slice, only for a next boot

[rank1seeker at gmail.com]

----- Original Message -----
From: Chris Rees <crees at freebsd.org>
To: rank1seeker at gmail.com
Cc: John Baldwin <jhb at freebsd.org>, hackers at freebsd.org
Date: Mon, 26 Mar 2012 21:28:07 +0000
Subject: Re: Active slice, only for a next boot

> On 26 March 2012 18:10,  <rank1seeker at gmail.com> wrote:
> > ----- Original Message -----
> > From: John Baldwin <jhb at freebsd.org>
> > To: freebsd-hackers at freebsd.org
> > Cc: rank1seeker at gmail.com, hackers at freebsd.org
> > Date: Mon, 26 Mar 2012 10:18:53 -0400
> > Subject: Re: Active slice, only for a next boot
> >
> >> On Sunday, March 25, 2012 2:49:17 pm rank1seeker at gmail.com wrote:
> >> > After having a thought about this issue and also currently looking at a
> >> BootEasy boot manager ...
> >> > 'boot0cfg' is almost perfect for this task and should/could be "exploited".
> >> >
> >> > It's '-o noupdate' already does a major task, of keeping main slice active.
> >> > Now all we need is a flag, through which we specify slice to boot (replacing
> >> human presing button).
> >> > From that point on, existing code simply proceeds with received value.
> >> >
> >> > '-o noupdate' ensures next boot will bring up main/active slice.
> >>
> >> You mean like 'boot0cfg -s 4'?
> >>
> >> --
> >> John Baldwin
> >>
> >
> >
> > Yes, but new flag for that purpose ('-n' for example => nextboot).
> >
> > I.e;
> >    # 'boot0cfg -s 4 -o noupdate -n 3'
> >
> > Would, set the default/main boot selection to slice 4 and  '-o noupdate'  ensures it remains that way, while '-n 3' would auto press/choose slice 3 in selection menu, as human would.
> > Well in that case, better to not show menu at all, thus only "blic" into slice 3.
> > At next boot it is at slice 4 again.
> 
> I'm afraid this sounds like a great way to make a very confusing
> scenario, where you have to reboot twice to be sure of a consistent
> boot sector, unless I've misunderstood you.
> 
> Chris


Let me put it this way.
'boot0cfg' should continue to behave as it does. Exactly in this form, it is a perfect (almost) solution.
This means that none of it's current flag shall be edited in terms of functionality, thus preserving backward compatibility with everthing.

So, on top of all it's code, we add just a 1 flag which auto selects boot option/slice, as human would from it's boot menu.
Simple as that. We can call that flag:
    -n nextboot slice
or maybe
    -a (auto)answer

On existing machine with active and booted, i.e; slice 3
# 'boot0cfg -n 1'
     Would upon next power on, instead showing boot menu, simply choose slice 3 to boot. Same result as if human would press F3 for slice 3.

Nothing more, nothing else. Simple as that.
It's indirect effect is determined by combination of other already existing flags, i.e; '-o noupdate'

In above example without '-o noupdate' it would also make slice 1 active.
Contrary to that, with specified  '-o noupdate' , it would boot slice 1 only once, preserving slice 3 as active (all furter boots stick to it)

It is now clearer?


Domagoj Smolčić