Booting from DOC Millenium

Booting from DOC Millenium

[Esben Nielsen]

Hya all,
 I see that Linux now have support for DOC Millenium(?). I have a PPC board here with 1 Mb NOR flash supposed to contain the bootsector and 64 DOC-M to hold the filesystem.

As I can see it I have the following options for booting:

1)  Have a small bootsector and used a compressed kernel in the 1Mb NOR. I don't like this solution, as I will only be able to have 1 kernel available. There is no room for a fall-back image if an update fails. I don't like this.

2) Get a bootsector which can read the kernel from the filesystem on the DOC.  Is there any such bootsector anywhere?

3) Go for a 3 stage boot: Have  a small bootsector which boots a small, never changed Linux kernel from the 1Mb NOR. That small kernel does one thing: read out the real kernel from the DOC. Do anyone have experience with such a strategy?

4) Use a small Linux as a bootsector. Compile the initial hardware setup in before decompression and instead of starting initrd make something like "kexec" to start the real, runtime kernel. Has anyone been playing with this?

Having to have a seperate bootsector for Linux is not very good. We otherwise use VxWorks here. In that context the bootsector is simply a scaled down version of VxWorks itself. I.e. we only have to worry about fitting one system to our hardware and just have to compile it in two versions. Last time I made Linux run on one of our boards (SA1110, NOR flash). I had to first to fit a bootsector, then fit Linux. Double work :-(

Regards,
Esben

Re: Booting from DOC Millenium

[jasmine]

On Mon, 11 Oct 2004, Esben Nielsen wrote:

> 1)  Have a small bootsector and used a compressed kernel in the 1Mb NOR.

This is a common strategy.

> 2) Get a bootsector which can read the kernel from the filesystem on the 
>    DOC.  Is there any such bootsector anywhere?

GRUB can do this.  If you're on a non-Intel platform, there are other
bootloaders that could be persuaded to do this.

> 3) Go for a 3 stage boot: Have a small bootsector which boots a small, 
>    never changed Linux kernel from the 1Mb NOR. That small kernel does 
>    one thing: read out the real kernel from the DOC. Do anyone have 
>    experience with such a strategy?

LinuxBIOS does this.

> 4) Use a small Linux as a bootsector. Compile the initial hardware setup 
>    in before decompression and instead of starting initrd make something 
>    like "kexec" to start the real, runtime kernel. Has anyone been 
>    playing with this?

...that's functionally the same as (3) above.

> Having to have a seperate bootsector for Linux is not very good. We 
> otherwise use VxWorks here.

Grub et al. can boot VxWorks.

-J.