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Brian Rose | 7 Feb 2003 18:41
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File system image


I am trying to build a NetBSD kernel with a built in MEMDRIVE that 
contains all the files that I need to run a machine. This is similiar to 
a diskless setup except that I am not mounting a drive via NFS.

I'm running into a bit of a paradox. I'll detail the working 
configuration first, then I'll show you where my trouble is...

WORKING SETUP - To create a 1.44Meg MEMDRIVE
--------------------------------------------
1) Zero the drive
   dd if=/dev/zero of=/dev/fd0a bs=512 count=2880
2) Create a new filesystem on the drive
   newfs /dev/fd0a floppy
3) Mount the floppy
   mount -t ffs /dev/fd0a /mnt/floppy
4) Copy the files
5) unmount the floppy
   umount /mnt/floppy
6) Copy the image
   dd if=/dev/fd0a of=memdrive.image
7) place the image into the kernel
   mdsetimage -s -v netbsd.memkernel memdrive.image
8) boot the new image!

Again, this works fine. The problem I am having is creating an arbitrary 
memdrive that is not based on any physical device. For example, I'd like 
to make a 16M memdrive. But I don't have any devices that have a 16M 
capacity that I can dd from. My next smallest device is my 4.3GB hard drive.
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David Laight | 7 Feb 2003 18:50
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Re: File system image

> 
> I tried using virtual devices, but you cannot disklabel a virtual 
> device.

man vnd

	David

--

-- 
David Laight: david <at> l8s.co.uk
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Perry E. Metzger | 7 Feb 2003 19:16
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Re: File system image


You should read the scripts that build NetBSD boot media. No physical
drives are used in the process at all.

Brian Rose <saider <at> gate.net> writes:

> I am trying to build a NetBSD kernel with a built in MEMDRIVE that
> contains all the files that I need to run a machine. This is similiar
> to a diskless setup except that I am not mounting a drive via NFS.
> 
> I'm running into a bit of a paradox. I'll detail the working
> configuration first, then I'll show you where my trouble is...
> 
> WORKING SETUP - To create a 1.44Meg MEMDRIVE
> --------------------------------------------
> 1) Zero the drive
>    dd if=/dev/zero of=/dev/fd0a bs=512 count=2880
[...]
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Brian Rose | 7 Feb 2003 20:17
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Re: File system image


Wojciech Puchar wrote:

>I tried using virtual devices, but you cannot disklabel a virtual
>  
>

why? could you please say what was a problem?

David Laight wrote:

>>I tried using virtual devices, but you cannot disklabel a virtual 
>>device.
>>    
>>
>
>man vnd
>
>	David
>  
>
I was doing some googling on the subject, and I came across some 
articles that mentioned that the virtual device driver does not have the 
proper ioctl routines that disklabel uses. I don't know the details. 
After I read several of these I decided to try to find a workaround. I 
tried the following with no errors...

1) dd if=/dev/zero of=fs_16M.img bs=512 count=32768
2) vnconfig -c -v /dev/rvnd0 fs_16M.img
3) fdisk -i /dev/vnd0
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Michael Kukat | 7 Feb 2003 19:13

Re: File system image

Hello,

On Fri, 7 Feb 2003, Brian Rose wrote:
> I tried using virtual devices, but you cannot disklabel a virtual
> device. And without a disklabel, you can't put a filesystem on an image
> using newfs. So how do I create a memdrive with a proper disklabel so
> that I can put a filesystem on it and boot from it? I've been looking
> all over trying various combinations of mdconfig, vnconfig, disklabel,
> fdisk, and other commands to try and force a disk label onto a memdrive
> or a virtual device.

It works with virtualk devices. Try this:

(assuming a virtual disk with 512 bytes blocksize, 64 sectors, 32 heads, 16
tracks = 16 MB)

[root <at> calchas tmp]# dd if=/dev/zero bs=512 count=$((64*32*16)) of=vdisk.img
[root <at> calchas tmp]# vnconfig vnd0 `pwd`/vdisk.img 512/64/32/16
[root <at> calchas tmp]# disklabel -eI vnd0
(edit your disklabel like you want it)
[root <at> calchas tmp]# newfs vnd0a
[root <at> calchas tmp]# mount /dev/vnd0a /mnt
(copy your files)
[root <at> calchas tmp]# umount /mnt
[root <at> calchas tmp]# vnconfig -u vnd0

Now, mdsetimage should work. Never tried this last step, but above, you just
have the directions how to make the filesystem in an any-sized virtual disk.
Looking at the values, just change the "16" in dd and in vnconfig to the value
in megs you want to use.
(Continue reading)

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Brian Rose | 7 Feb 2003 22:28
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Re: File system image

Perry E. Metzger wrote:

>You should read the scripts that build NetBSD boot media. No physical
>drives are used in the process at all.
>
>Brian Rose <saider <at> gate.net> writes:
>
>  
>
>>I am trying to build a NetBSD kernel with a built in MEMDRIVE that
>>contains all the files that I need to run a machine. This is similiar
>>to a diskless setup except that I am not mounting a drive via NFS.
>>
>>I'm running into a bit of a paradox. I'll detail the working
>>configuration first, then I'll show you where my trouble is...
>>
>>WORKING SETUP - To create a 1.44Meg MEMDRIVE
>>--------------------------------------------
>>1) Zero the drive
>>   dd if=/dev/zero of=/dev/fd0a bs=512 count=2880
>>    
>>
>[...]
>  
>

I was looking in that area and the problem I ran across was when I was 
trying to initialize the disklabel, I found that all the boot media seem 
to use either 1.44 Meg floppies or 2.88 Meg floppies, both of which have 
an entry in the disktab file.
(Continue reading)

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Perry E. Metzger | 7 Feb 2003 22:32
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Re: File system image


Brian Rose <saider <at> gate.net> writes:
> I was looking in that area and the problem I ran across was when I was
> trying to initialize the disklabel, I found that all the boot media
> seem to use either 1.44 Meg floppies or 2.88 Meg floppies, both of
> which have an entry in the disktab file.

The disklabel program doesn't need an actual functioning disktab to
operate -- indeed, the average drive running NetBSD doesn't have a
disktab. You can just run it -- try out disklabel -i for example.

And yes, you can run it on a vnd based file system (obbviously.)

> The main problem I am having is that my kernel won't boot. When I
> select it from the boot menu, it loads it up and resets the machine. I
> see the numbers as the kernel is loading, but it reboots immediately
> after, when the banner is usually displayed.
> 
> I'm going to be delving into the source code to find out what is going
> on, but if anyone can shed light as to what is happening, I'd
> appreciate it.

You might want to explain what you are loading this kernel from and
what the kernel has been configured to do.

--

-- 
Perry E. Metzger		perry <at> piermont.com
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Perry E. Metzger | 7 Feb 2003 22:46
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Re: File system image


Brian Rose <saider <at> gate.net> writes:
> I was doing some googling on the subject, and I came across some
> articles that mentioned that the virtual device driver does not have
> the proper ioctl routines that disklabel uses. I don't know the
> details. After I read several of these I decided to try to find a
> workaround. I tried the following with no errors...

You can set the "geometry" of your vnd device with vnconfig, fyi.

--

-- 
Perry E. Metzger		perry <at> piermont.com
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David Laight | 7 Feb 2003 23:12
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Re: File system image

> 11) FTP the test image to my test machine, reboot and at the boot 
> prompt, select netbsd.test as the kernel to boot.
> 
> The bootloader seems to load the kernel (I see the numbers) and then 
> reboots immediately.

You need to use the correct geometry of the target drive when you
build your image.  Otherwise it will go 'tits up'.

Actually you also have a problem unless the image is copies to the
bottom of the hard disk because part of teh boot sequence uses
absolute sector numbers.

	David

--

-- 
David Laight: david <at> l8s.co.uk
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Brian Rose | 8 Feb 2003 00:33
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Re: File system image


David Laight wrote:

>>11) FTP the test image to my test machine, reboot and at the boot 
>>prompt, select netbsd.test as the kernel to boot.
>>
>>The bootloader seems to load the kernel (I see the numbers) and then 
>>reboots immediately.
>>    
>>
>
>You need to use the correct geometry of the target drive when you
>build your image.  Otherwise it will go 'tits up'.
>
>Actually you also have a problem unless the image is copies to the
>bottom of the hard disk because part of teh boot sequence uses
>absolute sector numbers.
>
>
>	David
>  
>

I thought that the target drive would be irrelevant after booting. 
Here's some more background on my little project.

I am building for a i386 target. The machine is a PC104 sized system 
with a 2GB hard drive and a 32MB Disk-On-Chip. My goal is to develop a 
small NetBSD system that will fit on the DOC without the need for a hard 
drive. But for now I am booting off of the hard drive. There is no
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