Editing Machine Configuration

Talos node state is fully defined by machine configuration. Initial configuration is delivered to the node at bootstrap time, but configuration can be updated while the node is running.

There are three talosctl commands which facilitate machine configuration updates:

• talosctl apply-config to apply configuration from the file
• talosctl edit machineconfig to launch an editor with existing node configuration, make changes and apply configuration back
• talosctl patch machineconfig to apply automated machine configuration via JSON patch

Each of these commands can operate in one of four modes:

• apply change in automatic mode (default): reboot if the change can’t be applied without a reboot, otherwise apply the change immediately
• apply change with a reboot (--mode=reboot): update configuration, reboot Talos node to apply configuration change
• apply change immediately (--mode=no-reboot flag): change is applied immediately without a reboot, fails if the change contains any fields that can not be updated without a reboot
• apply change on next reboot (--mode=staged): change is staged to be applied after a reboot, but node is not rebooted
• apply change with automatic revert (--mode=try): change is applied immediately (if not possible, returns an error), and reverts it automatically in 1 minute if no configuration update is applied
• apply change in the interactive mode (--mode=interactive; only for talosctl apply-config): launches TUI based interactive installer

Note: applying change on next reboot (--mode=staged) doesn’t modify current node configuration, so next call to talosctl edit machineconfig --mode=staged will not see changes

Additionally, there is also talosctl get machineconfig -o yaml, which retrieves the current node configuration API resource and contains the machine configuration in the .spec field. It can be used to modify the configuration locally before being applied to the node.

The list of config changes allowed to be applied immediately in Talos v1.8.0:

• .debug
• .cluster
• .machine.time
• .machine.ca
• .machine.acceptedCAs
• .machine.certCANs
• .machine.install (configuration is only applied during install/upgrade)
• .machine.network
• .machine.nodeAnnotations
• .machine.nodeLabels
• .machine.nodeTaints
• .machine.sysfs
• .machine.sysctls
• .machine.logging
• .machine.controlplane
• .machine.kubelet
• .machine.pods
• .machine.kernel
• .machine.registries (CRI containerd plugin will not pick up the registry authentication settings without a reboot)
• .machine.features.kubernetesTalosAPIAccess
• .machine.features.hostDNS
• .machine.features.kubePrism

talosctl apply-config

This command is traditionally used to submit initial machine configuration generated by talosctl gen config to the node.

It can also be used to apply configuration to running nodes. The initial YAML for this is typically obtained using talosctl get machineconfig -o yaml | yq eval .spec >machs.yaml. (We must use yq because for historical reasons, get returns the configuration as a full resource, while apply-config only accepts the raw machine config directly.)

Example:

talosctl -n <IP> apply-config -f config.yaml

Command apply-config can also be invoked as apply machineconfig:

talosctl -n <IP> apply machineconfig -f config.yaml

Applying machine configuration immediately (without a reboot):

talosctl -n IP apply machineconfig -f config.yaml --mode=no-reboot

Starting the interactive installer:

talosctl -n IP apply machineconfig --mode=interactive

Note: when a Talos node is running in the maintenance mode it’s necessary to provide --insecure (-i) flag to connect to the API and apply the config.

talosctl edit machineconfig

Command talosctl edit loads current machine configuration from the node and launches configured editor to modify the config. If config hasn’t been changed in the editor (or if updated config is empty), update is not applied.

Note: Talos uses environment variables TALOS_EDITOR, EDITOR to pick up the editor preference. If environment variables are missing, vi editor is used by default.

Example:

talosctl -n <IP> edit machineconfig

Configuration can be edited for multiple nodes if multiple IP addresses are specified:

talosctl -n <IP1>,<IP2>,... edit machineconfig

Applying machine configuration change immediately (without a reboot):

talosctl -n <IP> edit machineconfig --mode=no-reboot

talosctl patch machineconfig

Command talosctl patch works similar to talosctl edit command - it loads current machine configuration, but instead of launching configured editor it applies a set of JSON patches to the configuration and writes the result back to the node.

Example, updating kubelet version (in auto mode):

$ talosctl -n <IP> patch machineconfig -p '[{"op": "replace", "path": "/machine/kubelet/image", "value": "ghcr.io/siderolabs/kubelet:v1.31.1"}]'
patched mc at the node <IP>

Updating kube-apiserver version in immediate mode (without a reboot):

$ talosctl -n <IP> patch machineconfig --mode=no-reboot -p '[{"op": "replace", "path": "/cluster/apiServer/image", "value": "registry.k8s.io/kube-apiserver:v1.31.1"}]'
patched mc at the node <IP>

A patch might be applied to multiple nodes when multiple IPs are specified:

talosctl -n <IP1>,<IP2>,... patch machineconfig -p '[{...}]'

Patches can also be sourced from files using @file syntax:

talosctl -n <IP> patch machineconfig -p @kubelet-patch.json -p @manifest-patch.json

It might be easier to store patches in YAML format vs. the default JSON format. Talos can detect file format automatically:

# kubelet-patch.yaml
- op: replace
  path: /machine/kubelet/image
  value: ghcr.io/siderolabs/kubelet:v1.31.1

talosctl -n <IP> patch machineconfig -p @kubelet-patch.yaml

Recovering from Node Boot Failures

If a Talos node fails to boot because of wrong configuration (for example, control plane endpoint is incorrect), configuration can be updated to fix the issue.