>> Can you demonstrate the benefits of your method with examples of how things 
>> become simpler?  (only tested-to-work examples, please, no should-work ones)


I’m not sure of any other way to configure the rump kernels network and disk 
except via json.cfg - is there any alternative way? Maybe I’ve missed some 
obvious way of getting json.cfg into the kernel.

Configuration of network-only unikernels is one good use case.

Currently I’m trying to load a unikernel which will not have any disk activity 
at all - just network. To do so, right now to get the network configured I have 
to be able to provide the unikernel with either an ext2 disk or boot from ISO, 
and the unikernel will automount and load the json.cfg from there.

To be specific, it turns out to be quite complex and fiddly to build bootable 
disk images that are either pure ext2 or alternatively ext4 with additional 
ext2 partitions that can be specified as the root partition to the rump kernel. 
 After having spent the past few days learning the ins and outs of boot 
process, grub, mbr & gpt partition tables etc and finding how brittle all that 
is, I’m thinking “all this to get an ext2 disk attached so I can load one 
configuration file which is less than 100 bytes, when it could be configured by 
directly passing that config into the kernel boot params, and its not even 
desireable to have the ext2 file system hanging around once I’ve got the config 
file”.   I should note out I’m trying to do this in a bare metal hardware 
configuration - not that this makes much difference to anything.

I know that’s just my problem but I do think it would be generally more useful 
if a kernel configuration could be passed in via the boot process rather than 
either compiled in or loaded from a disk automounted during boot - an 
automounted disk shouldn’t be needed for configuration loading. Loading 
json.cfg from automounted disks is probably a good thing to have as an option 
but getting those disks configured can add to the overall complexity of the 
setup - by a big margin if you’re not a deep-tech systems admin who knows all 
about disks and partitions and grub and stuff.

I’m not sure if I’m putting a good enough case.  If you’re not convinced, let 
me know and I’ll try to formulate a stronger argument that better articulates 
why I think this is valuable.

as


 

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