Talos provides a way to run additional system services early in the Talos boot process. Extension services should be included into the Talos root filesystem (e.g. using system extensions). Extension services run as privileged containers with ephemeral root filesystem located in the Talos root filesystem.
Extension services can be used to use extend core features of Talos in a way that is not possible via static pods or Kubernetes DaemonSets.
Potential extension services use-cases:
- storage: Open iSCSI, software RAID, etc.
- networking: BGP FRR, etc.
- platform integration: VMWare open VM tools, etc.
Talos on boot scans directory
*.yaml files describing the extension services to run.
Format of the extension service config:
name: hello-world container: entrypoint: ./hello-world args: - -f mounts: - # OCI Mount Spec depends: - service: cri - path: /run/machined/machined.sock - network: - addresses - connectivity - hostname - etcfiles - time: true restart: never|always|untilSuccess
name sets the service name, valid names are
The service container root filesystem path is derived from the
The extension service will be registered as a Talos service under an
entrypointdefines the container entrypoint relative to the container root filesystem (
argsdefines the additional arguments to pass to the entrypoint
mountsdefines the volumes to be mounted into the container root
mounts uses the standard OCI spec:
- source: /var/log/audit destination: /var/log/audit type: bind options: - rshared - bind - ro
All requested directories will be mounted into the extension service container mount namespace.
source directory doesn’t exist in the host filesystem, it will be created (only for writable paths in the Talos root filesystem).
security follows this example:
maskedPaths: - "/should/be/masked" readonlyPaths: - "/path/that/should/be/readonly" - "/another/readonly/path" writeableRootfs: true writeableSysfs: true
- The rootfs is readonly by default unless
writeableRootfs: trueis set.
- The sysfs is readonly by default unless
writeableSysfs: trueis set.
- Masked paths if not set defaults to containerd defaults. Masked paths will be mounted to
/dev/null. To set empty masked paths use:
container: security: maskedPaths: 
- Read Only paths if not set defaults to containerd defaults. Read-only paths will be mounted to
/dev/null. To set empty read only paths use:
container: security: readonlyPaths: 
depends section describes extension service start dependencies: the service will not be started until all dependencies are met.
service: <name>: wait for the service
<name>to be running and healthy
path: <path>: wait for the
network: [addresses, connectivity, hostname, etcfiles]: wait for the specified network readiness checks to succeed
time: true: wait for the NTP time sync
restart defines the service restart policy, it allows to either configure an always running service or a one-shot service:
always: restart service always
never: start service only once and never restart
untilSuccess: restart failing service, stop restarting on successful run
Example layout of the Talos root filesystem contents for the extension service:
/ └── usr └── local ├── etc │ └── containers │ └── hello-world.yaml └── lib └── containers └── hello-world ├── hello └── config.ini
Talos discovers the extension service configuration in
name: hello-world container: entrypoint: ./hello args: - --config - config.ini depends: - network: - addresses restart: always
Talos starts the container for the extension service with container root filesystem at
/ ├── hello └── config.ini
Extension service is registered as
$ talosctl service ext-hello-world NODE 172.20.0.5 ID ext-hello-world STATE Running HEALTH ? EVENTS [Running]: Started task ext-hello-world (PID 1100) for container ext-hello-world (2m47s ago) [Preparing]: Creating service runner (2m47s ago) [Preparing]: Running pre state (2m47s ago) [Waiting]: Waiting for service "containerd" to be "up" (2m48s ago) [Waiting]: Waiting for service "containerd" to be "up", network (2m49s ago)
An extension service can be started, restarted and stopped using
talosctl service ext-hello-world start|restart|stop.
talosctl logs ext-hello-world to get the logs of the service.
Complete example of the extension service can be found in the extensions repository.