Re: Can you MOP boot an install kernel directly?

And now I'm sure ragge is going to comment on how he experimented and 
got a boot block to actually load the kernel. :-D

Also, the boot block is only capable of reading /boot from the same 
device as the boot block is on. And it's not in any way interactive. It 
runs completely in one go to just get /boot running.

   Johnny

On 2025-08-05 06:52, Johnny Billquist wrote:
> On 2025-08-04 19:26, Perry Metzger wrote:
>> On 8/4/25 12:36, Jason Thorpe wrote:
>>>> On Aug 4, 2025, at 7:45 AM, Johnny Billquist<[email protected]>wrote:
>>>>
>>>> I'll just top-post to be lazy.
>>>>
>>>> First of all, as you know, MOP is the "native" way to netboot DEC 
>>>> machines from back in the day. And MOP sortof fills the place of 
>>>> both DHCP and TFTP in one. But it's more targeted for the explicit 
>>>> need of netbooting and remote management. But in a sense, for VAXen, 
>>>> it would be great if we had the possibility of getting all the 
>>>> netbooting though MOP and not need DHCP and TFTP. Not sure if that 
>>>> is possible, though.
>>> Can MOP supply the IP address to the system?  If not, you're not 
>>> goingto be eliminating DHCP (or BOOTP).
>>
>> Certainly, but it's nice not to have to load boot blocks that then 
>> just load the kernel if you can just load the kernel in one step. The 
>> OS will use dhclient to get its address.
> 
> I'm starting to suspect you don't understand the full process of the 
> booting.
> 
> The boot block is a really simple piece of code that resides in the 
> first block(s) of a disk, and the sole purpose of that code is to read 
> in the /boot image.
> 
> The /boot image in turn is responsible for reading in the kernel.
> 
> The boot block never reads in the kernel. It's not advanced enough to be 
> able to deal with that. And it can't be. There are limits on how much 
> code you can stash into the boot block.
> 
> If you substitute "/boot" for whenever you say "boot block", then you 
> are more in the right place. And MOP reads in /boot. And the next step 
> from there is reading in the kernel. But at the moment, dhcp is needed 
> here, because boot needs to know which address to fetch the kernel from, 
> as well as what filename to fetch, and some other bits. And then, once 
> the kernel have booted, it will also request what IP address itself 
> should use.
> 
> What would be nice would be if /boot, instead of depending on dhcp and 
> tftp, could use MOP as well, to get the kernel, as well as the 
> parameters for getting the kernel and its own configuration parameters. 
> Then you could probably skip tftp altogether, and dhcp would be more for 
> normal operation, and not needed for the initial booting.
> 
> Although, since dhcp would probably always be needed/used anyway, there 
> is probably less arguments for trying to remove that dependency.
> 
>    Johnny
> 

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: [email protected]             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol