Hello all,
I have a new laptop, on which I want to use a cgd'd root. I assumed I
would run into the same problems I encountered on my other computer, and
I was right (see PR 36963). In fact, it was even worse -- I couldn't
even get it to create multiple ttyE's; I was stuck with the console.
Installing without init.root makes the system a lot more useful. (Both
systems are running NetBSD/amd64 4.0).
So, it's pretty obvious what I need to do: I need to implement an
alternative way of getting cgd on root (or, rather, root on cgd).
I've been reading source code for the last couple of days, to get an
idea of where to start.
This is what I am thinking.
The following are added to the kernel-config:
option CGD_IS_ROOT
option CGDROOT_HW_DEV wd0a
option CGDROOT_DEV cgd0
option CGDROOT_PARAMFILE rootkey0
So, what does this mean? The first option is straightforward. The
second tells the kernel which slice which contains the cgd'd root. The
third the cgd device, and the fourth requires some explaining.
The big question is where to store the cgd parameter file. My goal is
to be able to boot from an USB memory stick. It should contain the
kernel I boot from, and the parameter file, so I have a separation
between the hard drive containing the root, and the parameter file.
But how do I read the parameter file without a root file system (I
don't want to have to mount root on the memory key, because then I'd be
stuck with it, afaict. And a memory disk would just lead to the troubles
of init.root). I was thinking about sticking the parameter file in a
kernel device. Something like "mdsetimage", but which stores an
arbistrary file in a kernel image.
makekerndevfile <kernel> <devname> <filename>
# makekerndevfile netbsd rootkey0 ~/rootkey.cgd
When the kernel boots, it can access the contents of the file as a
device (rootkey0), without using a filesystem. I'm not particularly fond
of this idea, to be honest, but it'll get the work done.
I got the tip, on IRC, to look into using property lists for storing
the parameter file. Is this a route I should look into more? What files
are relevant to read if I want to understand more about them?
The problems, as far as I can see:
1) N-factor keys won't be supported (easily).
2) Hardcoding root to be located on the 'a'-slice in the cgd-device
maybe isn't the neatest of solutions, but it'll do for now.
3) Recursive cgd container configurations aren't supported (are they
normally?).
Come to think of it, it would be much better if CGD_IS_ROOT,
CGDROOT_HW_DEV, CGDROOT_DEV, CGDROOT_PARAMFILE could simply use the
"config netbsd root on ? type ?" configuration specification in some manner.
config netbsd root on cgd0a
Hmm.. I need to look into that.
Ideas, hints, tips, requests are very welcome.
Questions will surely follow.
--
Kind regards,
Jan Danielsson
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