Components

In this section, we discuss the various components that underpin Talos.

Components

Talos Linux and Kubernetes are tightly integrated.

In the following, the focus is on the Talos Linux specific components.

apid

When interacting with Talos, the gRPC api endpoint you will interact with directly is apid. Apid acts as the gateway for all component interactions. Apid provides a mechanism to route requests to the appropriate destination when running on a control plane node.

We’ll use some examples below to illustrate what apid is doing.

When a user wants to interact with a Talos component via talosctl, there are two flags that control the interaction with apid. The -e | --endpoints flag specifies which Talos node ( via apid ) should handle the connection. Typically this is a public-facing server. The -n | --nodes flag specifies which Talos node(s) should respond to the request. If --nodes is omitted, the first endpoint will be used.

Note: Typically, there will be an endpoint already defined in the Talos config file. Optionally, nodes can be included here as well.

For example, if a user wants to interact with machined, a command like talosctl -e cluster.talos.dev memory may be used.

$ talosctl -e cluster.talos.dev memory
NODE                TOTAL   USED   FREE   SHARED   BUFFERS   CACHE   AVAILABLE
cluster.talos.dev   7938    1768   2390   145      53        3724    6571

In this case, talosctl is interacting with apid running on cluster.talos.dev and forwarding the request to the machined api.

If we wanted to extend our example to retrieve memory from another node in our cluster, we could use the command talosctl -e cluster.talos.dev -n node02 memory.

$ talosctl -e cluster.talos.dev -n node02 memory
NODE    TOTAL   USED   FREE   SHARED   BUFFERS   CACHE   AVAILABLE
node02  7938    1768   2390   145      53        3724    6571

The apid instance on cluster.talos.dev receives the request and forwards it to apid running on node02, which forwards the request to the machined api.

We can further extend our example to retrieve memory for all nodes in our cluster by appending additional -n node flags or using a comma separated list of nodes ( -n node01,node02,node03 ):

$ talosctl -e cluster.talos.dev -n node01 -n node02 -n node03 memory
NODE     TOTAL    USED    FREE     SHARED   BUFFERS   CACHE   AVAILABLE
node01   7938     871     4071     137      49        2945    7042
node02   257844   14408   190796   18138    49        52589   227492
node03   257844   1830    255186   125      49        777     254556

The apid instance on cluster.talos.dev receives the request and forwards it to node01, node02, and node03, which then forwards the request to their local machined api.

containerd

Containerd provides the container runtime to launch workloads on Talos and Kubernetes.

Talos services are namespaced under the system namespace in containerd, whereas the Kubernetes services are namespaced under the k8s.io namespace.

machined

A common theme throughout the design of Talos is minimalism. We believe strongly in the UNIX philosophy that each program should do one job well. The init included in Talos is one example of this, and we are calling it “machined”.

We wanted to create a focused init that had one job - run Kubernetes. To that extent, machined is relatively static in that it does not allow for arbitrary user-defined services. Only the services necessary to run Kubernetes and manage the node are available. This includes:

• containerd
• etcd
• kubelet
• networkd
• trustd
• udevd

The machined process handles all machine configuration, API handling, resource and controller management.

kernel

The Linux kernel included with Talos is configured according to the recommendations outlined in the Kernel Self Protection Project (KSPP).

trustd

Security is one of the highest priorities within Talos. To run a Kubernetes cluster, a certain level of trust is required to operate a cluster. For example, orchestrating the bootstrap of a highly available control plane requires sensitive PKI data distribution.

To that end, we created trustd. Based on a Root of Trust concept, trustd is a simple daemon responsible for establishing trust within the system. Once trust is established, various methods become available to the trustee. For example, it can accept a write request from another node to place a file on disk.

Additional methods and capabilities will be added to the trustd component to support new functionality in the rest of the Talos environment.

udevd

Udevd handles the kernel device notifications and sets up the necessary links in /dev.