[Nix-dev] NixOps: distributed builds, arm7vl

[Drew Hess]

Hi all,

I just wrapped up my first NixOps deployment. It’s lovely! Now I’m
ready to proceed to the next stage, and I could use a little guidance.
Here's where I am currently:

- I use a dedicated NixOS host, which I manage by hand (i.e., not with
  NixOps), as a “command-and-control” (CnC) host for my NixOps
  deployments.

- The current deployment is just 2 x86_64-linux physical hosts. These
  machines are fully managed by NixOps from the CnC host.

Here is where I'd like to get to next:

- Add multiple BeagleBone Black (armv7l architecture) hosts to the
  existing NixOps deployment. These will run various services and
  sensors.

- Use a dedicated armv7l build slave for the armv7l package builds.
  The BeagleBone Blacks (BBBs) are seriously underpowered and should 
  never do their own builds.

I just installed NixOS on a Jetson TK1. I would like to use it as the
armv7l build slave since it has pretty decent specs for an armv7l
machine. Currently, it is managed by hand, i.e., not in NixOps.

Here are my questions:

1. Are there any potential problems that arise from managing build
   slaves that are intended for use in NixOps deployments in the
   NixOps deployment itself? Should build slaves be managed by hand,
   like the CnC host? I’m not sure how NixOS’s support for
   distributed builds interacts and/or interferes with NixOps’s 
   deployments.

2. Does NixOps support both x86_64-linux and armv7l physical host
   targets in the same deployment? Do I need to specify that a
   particular target is armv7l, or will NixOps figure that out when it
   adds the host to the database?

3. Is there a way to ensure that NixOps only uses the dedicated armv7l
   build slave for armv7l builds, and never performs builds on the 
   other armv7l targets that it has deployed? I would prefer that
   deployments fail — say, because the dedicated build slave is down —
   than builds ever happen on the BeagleBones.

Thanks!

d