ARM Architecture Now Available

CI/CD
Jul 21, 2025
Dan Manges
ARM Architecture Now Available

We just shipped support for running Arm64 on RWX.

Building Arm containers is 10x faster without emulation. We built the initial RWX image for Arm64 by running on x86_64 with qemu, and it took 14m 8s to build the image. Now that we can build the RWX image for Arm on Arm, it runs in 1m 38s

Configuring RWX to use Arm64

You can specify the architecture in the base configuration.

.rwx/ci.yml
base:
  os: ubuntu 24.04
  tag: 1.2
  arch: arm64


tasks:
  - key: uname
    run: uname -a

Bootstrapping Support for Arm

We built the original Arm64 base images on RWX by running on x64_64 and using QEMU emulation.

Of course, now that we support Arm64, we can remove the emulation and build Arm on Arm.

Removing our bootstrapping and running natively was an easy and satisfying diff.

diff --git a/.rwx/build.yml b/.rwx/build.yml
index d807965..4312a60 100644
--- a/.rwx/build.yml
+++ b/.rwx/build.yml
@@ -6,6 +6,7 @@
 base:
   os: ubuntu 24.04
   tag: 1.2
+  arch: ${{ init.arch }}
 
 aliases:
   aws_sandbox: &aws_sandbox
@@ -67,9 +68,7 @@ tasks:
         DOCKER_ARCH="amd64"
       fi
 
-      docker buildx create --name multiarch --driver docker-container --bootstrap
-      docker buildx use multiarch
-      docker buildx build --platform linux/$DOCKER_ARCH --file "$DOCKERFILE" --tag "$docker_tag" . --output type=docker
+      docker build --file "$DOCKERFILE" --tag "$docker_tag" . --output type=docker
 
       fullImageDigest=$(docker inspect --format '{{.Id}}' "$docker_tag")
       echo "$fullImageDigest" | grep '^sha256:'

Demo

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