WARNING: new settings may not be used until builder is restarted

[wscourge]

When I run the following docker buildx create:

# Note: "$ " preceedes a line of input, "> " preceedes a line of output

$ docker buildx create \
  --name amd64_builder \
  --node amd64_builder \
  --platform linux/amd64 \
  "ssh://<MY_USER>@<IP>"

> WARNING: new settings may not be used until builder is restarted
> amd64_builder

it exits with 0 (does not fail), but produces the warning:

WARNING: new settings may not be used until builder is restarted

and when I docker buildx ls my builders, I see it is indeed inactive:

$ docker buildx ls

> NAME/NODE       DRIVER/ENDPOINT          STATUS   BUILDKIT             PLATFORMS
> amd64_builder * remote
>   amd64_builder ssh://<MY_USER>@<IP>     inactive                      linux/amd64*
> default         docker
>   default       default                  running  v0.12.2+6560bb937e8c linux/arm64, > linux/amd64, linux/amd64/v2, linux/riscv64, linux/ppc64le, linux/s390x, linux/mips64le, linux/mips64
> desktop-linux   docker
>   desktop-linux desktop-linux            running  v0.12.2+6560bb937e8c linux/arm64, linux/amd64, linux/amd64/v2, linux/riscv64, linux/ppc64le, linux/s390x, linux/mips64le, linux/mips64

I am able to ssh <MY_USER>@<IP> (with all the valid ~/.ssh/config in place).

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Question (originally asked on SO): What is the meaning of inactive, and how do I properly activate my builder?