'FROM' and 'COPY' unknown flag in Dockerfile


I am trying to build a linuxkit/kernel-4.9.x for ARM64 platform, since no aarch64 image available in the public linuxkit hub, so I have to build this aarch64 linuxkit kernel image by myself. But when I call ‘docker build’ upon the linuxkit/kernel/Dockerfile, the docker complains that it can’t recognize the ‘FROM linuxkit/kernel-compile:1b396c221af673757703258159ddc8539843b02b@sha256:6b32d205bfc6407568324337b707d195d027328dbfec554428ea93e7b0a8299b AS kernel-build’, seems the docker build can’t recognize the ’ AS kernel-build’ saying it’s ‘invalid repository/tag’, if I delete it from that line, the docker build will fail at ‘COPY --from=kernel-build /out/* /’, the ‘–from’ flag can not be recognized by ‘docker build’ either.

Any tips about this?

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You need install Docker Edge, “multi-stage builds” supported only in “edge” channel.