Subject: Re: NetBSD and root fs
To: Hubert Feyrer <>
From: Marcin Jessa <>
List: tech-embed
Date: 03/30/2005 22:16:19
On Wed, 30 Mar 2005 16:23:09 +0200 (CEST)
Hubert Feyrer <> wrote:

> This looks good. What it does is reserve space in the kernel, where you 
> can put a filesystem (ramdisk) with (I think) mdsetimage(8).

I do not want to put anything in the kernel except the "typical kernel stuff". 
What I do not know is if the boot loader (stage 2) is enable of uncompressing and mounting the root fs as a memory file system. I just cannot find any info of how it is done on the net.
I would like to have a / with only the kernel and boot in it.
Then a compressed memory mounted root file system with typical dirs and corresponding files:
/dev, /lib, /mnt, /root, /tmp, /var, /bin, /etc, /libexec, /proc, /sbin, /usr
The boot loader would put the kernel into memory, then kernel modules next (including the root-mfs), then force root on memory disk and execute /sbin/init (or /bin/sh if in single user mode).

The advantage of this approach is you can easly replace the compressed root fs which would work like a kind of firmware.
You can upload new one with ftp or over http and reboot your box and you have new upgraded software keeping your configs on a rw slice on the CF.

So my question is, is that possible to do with NetBSD?
How to load the root file system on memory disk at boot?
I assume the option MEMORY_DISK_IS_ROOT will be used by kernel once the root-mfs is loaded.