Build firecracker from a submodule.

[sipsma]

This is intended to ease development with Firecracker and version upgrades.

Signed-off-by: Erik Sipsma [email protected]

Note this does not upgrade Firecracker to a new version ( ref #259 ), it keeps the version at 0.17 for now, but it should make moving to 0.18 easier.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[samuelkarp]

1. Any particular reason you're using -stretch instead of the default or instead of -buster?

[sipsma]

I did not see a buster image for rust 1.32 on dockerhub (only for newer rust versions), so I don't think they ever released one.

[mxpv]

2. We probably should target same version of Rust as Firecracker:
   https://github.com/firecracker-microvm/firecracker/blob/master/tools/devctr/Dockerfile.x86_64#L7
   (or even we may consider using the Dockerfile from their repo as base to keep up)

[sipsma]

That Dockerfile is for Firecracker v0.18 (which updates to rust 1.35). We are still building Firecracker v0.17 for now, which uses an older rust toolchain.

I considered using their Dockerfile, but it's doing a lot more than we need here and not necessarily compatible with the way we structure our CI system, so I felt it would be simpler overall for us to just have this tiny Dockerfile of our own. We can reconsider in the future if maintaining this Dockerfile becomes meaningful overhead.

[nmeyerhans]

No major concerns, so feel free to merge. We can revisit my questions at a later time if you don't want to address them here. (please at least add comments and/or issues so they don't get lost)

[nmeyerhans]

Can we make these paths architecture independent without too much work? At some point we'll need arm64, at least.

[sipsma]

Yeah, for now I just updated to use an explicit FIRECRACKER_TARGET var that is used in the Makefile and also passed to the Dockerfile as a build-arg.

[nmeyerhans]

these docker commands should be prefixed with '-' so they don't count as a failure if a given image doesn't exist.

Raise the bar by providing a make function that checks to see if an image exists, exits true if not, tries to delete it if so (at that point you can fail meaningfully if it doesn't exist)

[sipsma]

I learned some more Make and added a macro for conditionally deleting the images. For the docker volume, the "-f" gets us that effect already (there is also a -f flag for rmi but it does much more that we don't want).

[nmeyerhans]

Same question as above regarding architecture independent paths.