[kata-dev] Shimv2 and CRI-O clarifications

David Gibson kata-dev at gibson.dropbear.id.au
Thu Feb 11 02:53:55 UTC 2021


Hi, hoping somebody can clear up a couple of points of confusion for
me.

1) The shimv2 protocol

AIUI, the shimv2 protocol has basically the same semantics as the OCI
runtime spec, but is over gRPC instead of a command line interface.
Is that correct?  Is there somewhere to find the spec of the shimv2
protocol?


2) CRI-O "runtime_type" option

The CRI-O configuration has a "runtime_type" variable for each
runtime, with options of "oci" or "vm".  What exactly the difference
between those is kind of unclear: what docs I've found say that "vm"
is more suitable for VM based runtimes, but I can't really see any
reason that would make a difference for crio.  Looking at the code it
looks like "vm" switches CRI-O to use the "shimv2" grpc based
interface rather than command line.  It makes sense CRI-O would need
to know that, but AFAICT it has nothing whatsoever to do with whether
the runtime uses a VM.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson
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