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This guide outlines steps and tricks to develop Talos operating systems and related components. The guide assumes Linux operating system on the development host. Some steps might work under Mac OS X, but using Linux is highly advised.

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Prepare

Check out the Talos repository. Try running make help to see available make commands. You would need Docker and buildx installed on the host.
Note: Usually it is better to install up to date Docker from Docker apt repositories, e.g. Ubuntu instructions. If buildx plugin is not available with OS docker packages, it can be installed as a plugin from GitHub releases.
Set up a builder with access to the host network: 
 docker buildx create --driver docker-container  --driver-opt network=host --name local1 --buildkitd-flags '--allow-insecure-entitlement security.insecure' --use
Note: network=host allows buildx builder to access host network, so that it can push to a local container registry (see below).
Make sure the following steps work:
  • make talosctl
  • make initramfs kernel
Set up a local docker registry: 
docker run -d -p 5005:5000 \
    --restart always \
    --name local registry:2
Try to build and push to local registry an installer image: 
make installer IMAGE_REGISTRY=127.0.0.1:5005 PUSH=true
Record the image name output in the step above.
Note: it is also possible to force a stable image tag by using TAG variable: make installer IMAGE_REGISTRY=127.0.0.1:5005 TAG=v1.0.0-alpha.1 PUSH=true.

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Running Talos cluster

Set up local caching docker registries (this speeds up Talos cluster boot a lot), script is in the Talos repo: 
bash hack/start-registry-proxies.sh
Start your local cluster with: 
sudo --preserve-env=HOME _out/talosctl-linux-amd64 cluster create \
    --provisioner=qemu \
    --cidr=172.20.0.0/24 \
    --registry-mirror docker.io=http://172.20.0.1:5000 \
    --registry-mirror registry.k8s.io=http://172.20.0.1:5001  \
    --registry-mirror gcr.io=http://172.20.0.1:5003 \
    --registry-mirror ghcr.io=http://172.20.0.1:5004 \
    --registry-mirror 127.0.0.1:5005=http://172.20.0.1:5005 \
    --install-image=127.0.0.1:5005/siderolabs/installer:<RECORDED HASH from the build step> \
    --controlplanes 3 \
    --workers 2 \
    --with-bootloader=false
  • --provisioner selects QEMU vs. default Docker
  • custom --cidr to make QEMU cluster use different network than default Docker setup (optional)
  • --registry-mirror uses the caching proxies set up above to speed up boot time a lot, last one adds your local registry (installer image was pushed to it)
  • --install-image is the image you built with make installer above
  • --controlplanes & --workers configure cluster size, choose to match your resources; 3 controlplanes give you HA control plane; 1 controlplane is enough, never do 2 controlplanes
  • --with-bootloader=false disables boot from disk (Talos will always boot from _out/vmlinuz-amd64 and _out/initramfs-amd64.xz). This speeds up development cycle a lot - no need to rebuild installer and perform install, rebooting is enough to get new code.
Note: as boot loader is not used, it’s not necessary to rebuild installer each time (old image is fine), but sometimes it’s needed (when configuration changes are done and old installer doesn’t validate the config). talosctl cluster create derives Talos machine configuration version from the install image tag, so sometimes early in the development cycle (when new minor tag is not released yet), machine config version can be overridden with —talos-version=.
If the --with-bootloader=false flag is not enabled, for Talos cluster to pick up new changes to the code (in initramfs), it will require a Talos upgrade (so new installer should be built). With --with-bootloader=false flag, Talos always boots from initramfs in _out/ directory, so simple reboot is enough to pick up new code changes. If the installation flow needs to be tested, --with-bootloader=false shouldn’t be used.

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Console Logs

Watching console logs is easy with tail: 
tail -F ~/.talos/clusters/talos-default/talos-default-*.log

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Interacting with Talos

Once talosctl cluster create finishes successfully, talosconfig and kubeconfig will be set up automatically to point to your cluster. Start playing with talosctl: 
talosctl -n 172.20.0.2 version
talosctl -n 172.20.0.3,172.20.0.4 dashboard
talosctl -n 172.20.0.4 get members
Same with kubectl: 
kubectl get nodes -o wide
You can deploy some Kubernetes workloads to the cluster. You can edit machine config on the fly with talosctl edit mc --immediate, config patches can be applied via --config-patch flags, also many features have specific flags in talosctl cluster create.

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Quick Reboot

To reboot whole cluster quickly (e.g. to pick up a change made in the code): 
for socket in ~/.talos/clusters/talos-default/talos-default-*.monitor; do echo "q" | sudo socat - unix-connect:$socket; done
Sending q to a single socket allows to reboot a single node.
Note: This command performs immediate reboot (as if the machine was powered down and immediately powered back up), for normal Talos reboot use talosctl reboot.

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Development Cycle

Fast development cycle:
  • bring up a cluster
  • make code changes
  • rebuild initramfs with make initramfs
  • reboot a node to pick new initramfs
  • verify code changes
  • more code changes…
Some aspects of Talos development require to enable bootloader (when working on installer itself), in that case quick development cycle is no longer possible, and cluster should be destroyed and recreated each time.

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Running Integration Tests

If integration tests were changed (or when running them for the first time), first rebuild the integration test binary: 
rm -f  _out/integration-test-linux-amd64; make _out/integration-test-linux-amd64
Running short tests against QEMU provisioned cluster: 
_out/integration-test-linux-amd64 \
    -talos.provisioner=qemu \
    -test.v \
    -talos.crashdump=false \
    -test.short \
    -talos.talosctlpath=$PWD/_out/talosctl-linux-amd64
Whole test suite can be run removing -test.short flag. Specfic tests can be run with -test.run=TestIntegration/api.ResetSuite.

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Build Flavors

make <something> WITH_RACE=1 enables Go race detector, Talos runs slower and uses more memory, but memory races are detected. make <something> WITH_DEBUG=1 enables Go profiling and other debug features, useful for local development.

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Destroying Cluster

sudo --preserve-env=HOME ../talos/_out/talosctl-linux-amd64 cluster destroy --provisioner=qemu
This command stops QEMU and helper processes, tears down bridged network on the host, and cleans up cluster state in ~/.talos/clusters.
Note: if the host machine is rebooted, QEMU instances and helpers processes won’t be started back. In that case it’s required to clean up files in ~/.talos/clusters/<cluster-name> directory manually.

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Optional

Set up cross-build environment with: 
docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
Note: the static qemu binaries which come with Ubuntu 21.10 seem to be broken.

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Unit tests

Unit tests can be run in buildx with make unit-tests, on Ubuntu systems some tests using loop devices will fail because Ubuntu uses low-index loop devices for snaps. Most of the unit-tests can be run standalone as well, with regular go test, or using IDE integration: 
go test -v ./internal/pkg/circular/
This provides much faster feedback loop, but some tests require either elevated privileges (running as root) or additional binaries available only in Talos rootfs (containerd tests). Running tests as root can be done with -exec flag to go test, but this is risky, as test code has root access and can potentially make undesired changes: 
go test -exec sudo  -v ./internal/app/machined/pkg/controllers/network/...

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Go Profiling

Build initramfs with debug enabled: make initramfs WITH_DEBUG=1. Launch Talos cluster with bootloader disabled, and use go tool pprof to capture the profile and show the output in your browser: 
go tool pprof http://172.20.0.2:9982/debug/pprof/heap
The IP address 172.20.0.2 is the address of the Talos node, and port :9982 depends on the Go application to profile:
  • 9981: apid
  • 9982: machined
  • 9983: trustd

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Testing Air-gapped Environments

There is a hidden talosctl debug air-gapped command which launches two components:
  • HTTP proxy capable of proxying HTTP and HTTPS requests
  • HTTPS server with a self-signed certificate
The command also writes down Talos machine configuration patch to enable the HTTP proxy and add a self-signed certificate to the list of trusted certificates: 
$ talosctl debug air-gapped --advertised-address 172.20.0.1
2022/08/04 16:43:14 writing config patch to air-gapped-patch.yaml
2022/08/04 16:43:14 starting HTTP proxy on :8002
2022/08/04 16:43:14 starting HTTPS server with self-signed cert on :8001
The --advertised-address should match the bridge IP of the Talos node. Generated machine configuration patch looks like: 
machine:
    files:
        - content: |
            -----BEGIN CERTIFICATE-----
            MIIBijCCAS+gAwIBAgIBATAKBggqhkjOPQQDAjAUMRIwEAYDVQQKEwlUZXN0IE9u
            bHkwHhcNMjIwODA0MTI0MzE0WhcNMjIwODA1MTI0MzE0WjAUMRIwEAYDVQQKEwlU
            ZXN0IE9ubHkwWTATBgcqhkjOPQIBBggqhkjOPQMBBwNCAAQfOJdaOFSOI1I+EeP1
            RlMpsDZJaXjFdoo5zYM5VYs3UkLyTAXAmdTi7JodydgLhty0pwLEWG4NUQAEvip6
            EmzTo3IwcDAOBgNVHQ8BAf8EBAMCBaAwHQYDVR0lBBYwFAYIKwYBBQUHAwEGCCsG
            AQUFBwMCMA8GA1UdEwEB/wQFMAMBAf8wHQYDVR0OBBYEFCwxL+BjG0pDwaH8QgKW
            Ex0J2mVXMA8GA1UdEQQIMAaHBKwUAAEwCgYIKoZIzj0EAwIDSQAwRgIhAJoW0z0D
            JwpjFcgCmj4zT1SbBFhRBUX64PHJpAE8J+LgAiEAvfozZG8Or6hL21+Xuf1x9oh4
            /4Hx3jozbSjgDyHOLk4=
            -----END CERTIFICATE-----
          permissions: 0o644
          path: /etc/ssl/certs/ca-certificates
          op: append
    env:
        http_proxy: http://172.20.0.1:8002
        https_proxy: http://172.20.0.1:8002
        no_proxy: 172.20.0.1/24
cluster:
    extraManifests:
        - https://172.20.0.1:8001/debug.yaml
The first section appends a self-signed certificate of the HTTPS server to the list of trusted certificates, followed by the HTTP proxy setup (in-cluster traffic is excluded from the proxy). The last section adds an extra Kubernetes manifest hosted on the HTTPS server. The machine configuration patch can now be used to launch a test Talos cluster: 
talosctl cluster create ... --config-patch @air-gapped-patch.yaml
The following lines should appear in the output of the talosctl debug air-gapped command:
  • CONNECT discovery.talos.dev:443: the HTTP proxy is used to talk to the discovery service
  • http: TLS handshake error from 172.20.0.2:53512: remote error: tls: bad certificate: an expected error on Talos side, as self-signed cert is not written yet to the file
  • GET /debug.yaml: Talos successfully fetches the extra manifest successfully
There might be more output depending on the registry caches being used or not.

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Running Upgrade Integration Tests

Talos has a separate set of provision upgrade tests, which create a cluster on older versions of Talos, perform an upgrade, and verify that the cluster is still functional. Build the test binary: 
rm -f  _out/integration-test-provision-linux-amd64; make _out/integration-test-provision-linux-amd64
Prepare the test artifacts for the upgrade test: 
make release-artifacts
Build and push an installer image for the development version of Talos: 
make installer IMAGE_REGISTRY=127.0.0.1:5005 PUSH=true
Run the tests (the tests will create the cluster on the older version of Talos, perform an upgrade, and verify that the cluster is still functional): 
sudo --preserve-env=HOME _out/integration-test-provision-linux-amd64 \
    -test.v \
    -talos.talosctlpath _out/talosctl-linux-amd64 \
    -talos.provision.target-installer-registry=127.0.0.1:5005 \
    -talos.provision.registry-mirror 127.0.0.1:5005=http://172.20.0.1:5005,docker.io=http://172.20.0.1:5000,registry.k8s.io=http://172.20.0.1:5001,quay.io=http://172.20.0.1:5002,gcr.io=http://172.20.0.1:5003,ghcr.io=http://172.20.0.1:5004 \
    -talos.provision.cidr 172.20.0.0/24