Locking a file backed mdconfig into memory

[Garrett Cooper]

On Fri, May 28, 2010 at 5:48 PM, Garrett Cooper <yanefbsd at gmail.com> wrote:
> On Fri, May 28, 2010 at 2:58 PM, Jeremy Chadwick
> <freebsd at jdc.parodius.com> wrote:
>> On Fri, May 28, 2010 at 12:26:12PM -0700, Dave Hayes wrote:
>>> Jeremy Chadwick <freebsd at jdc.parodius.com> writes:
>>> > And I think you meant this for variable names, in addition to what
>>> > vfs.root.mountfrom should be (specific to RELENG_8):
>>> > mfsroot_load="YES"
>>> > mfsroot_type="mfs_root"
>>> > mfsroot_name="/some/path/mfsroot"
>>>
>>> I'm using RELENG_7, but it seems rootfs_* works just like mfsroot_* ...
>>> is the former deprecated?
>>
>> I spent a small bit of time looking through both RELENG_7 and RELENG_8
>> source (/usr/src) as well as /boot (for the Forth portion) and I was
>> unable to find any reference to "rootfs" aside from actual variable
>> names (not loader variables) in C code or include files.  None were
>> strings.  There's a strong possibility I'm not looking the right way
>> (grep -ri ...).
>
> I vaguely remember reading about rootfs in the past, but it's
> definitely mfs_root now.
>
> This is how I do it in my quickie loader.rc:
>
> include /boot/loader.4th
> set vfs.root.mountfrom="ufs:/dev/md0"
> load /kernel
> load -t mfs_root /mfsroot
> start
>
>> I can assure you that mfsroot_xxx works on both platforms because I
>> wrote the below documentation:
>>
>> http://jdc.parodius.com/freebsd/pxeboot_serial_install.html
>>
>>> > vfs.root.mountfrom="ufs:/dev/md0"
>>>
>>> Hm, 'ufs:md0' currently works. What trouble can be had from using
>>> the abbreviated device name?
>>
>> I have no idea; probably none.  This is just the first time I've seen
>> the variable set to something "shorthand".  I would have to review
>> the parser code to see how it works.
>
> All depends on how you create the mfsroot. makefs(8) style mfsroots
> for instance are like /dev/md0a blah.

Ugh. Please ignore this statement. It's wrong..

> It also depends on your version of FreeBSD IIRC, because (again IIRC)
> GEOM changed the status quo in either 7.x or 8.x as to how md(4)
> devices represented. Again, this is IIRC :P!