This page focuses on the options that can be used when you set up K3s for the first time:

In addition to configuring K3s with environment variables and CLI arguments, K3s can also use a config file.

For more advanced options, refer to this page.

Throughout the K3s documentation, you will see some options that can be passed in as both command flags and environment variables. For help with passing in options, refer to How to Use Flags and Environment Variables.

Options for Installation with Script

As mentioned in the Quick-Start Guide, you can use the installation script available at https://get.k3s.io to install K3s as a service on systemd and openrc based systems.

The simplest form of this command is as follows:

curl -sfL https://get.k3s.io | sh -

When using this method to install K3s, the following environment variables can be used to configure the installation:

Environment Variable Description
INSTALL_K3S_SKIP_DOWNLOAD If set to true will not download K3s hash or binary.
INSTALL_K3S_SYMLINK By default will create symlinks for the kubectl, crictl, and ctr binaries if the commands do not already exist in path. If set to ‘skip’ will not create symlinks and ‘force’ will overwrite.
INSTALL_K3S_SKIP_ENABLE If set to true will not enable or start K3s service.
INSTALL_K3S_SKIP_START If set to true will not start K3s service.
INSTALL_K3S_VERSION Version of K3s to download from Github. Will attempt to download from the stable channel if not specified.
INSTALL_K3S_BIN_DIR Directory to install K3s binary, links, and uninstall script to, or use /usr/local/bin as the default.
INSTALL_K3S_BIN_DIR_READ_ONLY If set to true will not write files to INSTALL_K3S_BIN_DIR, forces setting INSTALL_K3S_SKIP_DOWNLOAD=true.
INSTALL_K3S_SYSTEMD_DIR Directory to install systemd service and environment files to, or use /etc/systemd/system as the default.
INSTALL_K3S_EXEC Command with flags to use for launching K3s in the service. If the command is not specified, and the K3S_URL is set, it will default to “agent.” If K3S_URL not set, it will default to “server.” For help, refer to this example.
INSTALL_K3S_NAME Name of systemd service to create, will default to ‘k3s’ if running k3s as a server and ‘k3s-agent’ if running k3s as an agent. If specified the name will be prefixed with ‘k3s-’.
INSTALL_K3S_TYPE Type of systemd service to create, will default from the K3s exec command if not specified.
INSTALL_K3S_SELINUX_WARN If set to true will continue if k3s-selinux policy is not found.
INSTALL_K3S_SKIP_SELINUX_RPM If set to true will skip automatic installation of the k3s RPM.
INSTALL_K3S_CHANNEL_URL Channel URL for fetching K3s download URL. Defaults to https://update.k3s.io/v1-release/channels.
INSTALL_K3S_CHANNEL Channel to use for fetching K3s download URL. Defaults to “stable”. Options include: stable, latest, testing.

Environment variables which begin with K3S_ will be preserved for the systemd and openrc services to use.

Setting K3S_URL without explicitly setting an exec command will default the command to “agent”.

When running the agent K3S_TOKEN must also be set.

Installing K3s from the Binary

As stated, the installation script is primarily concerned with configuring K3s to run as a service. If you choose to not use the script, you can run K3s simply by downloading the binary from our release page, placing it on your path, and executing it. The K3s binary supports the following commands:

Command Description
k3s server Run the K3s management server, which will also launch Kubernetes control plane components such as the API server, controller-manager, and scheduler.
k3s agent Run the K3s node agent. This will cause K3s to run as a worker node, launching the Kubernetes node services kubelet and kube-proxy.
k3s kubectl Run an embedded kubectl CLI. If the KUBECONFIG environment variable is not set, this will automatically attempt to use the config file that is created at /etc/rancher/k3s/k3s.yaml when launching a K3s server node.
k3s crictl Run an embedded crictl. This is a CLI for interacting with Kubernetes’s container runtime interface (CRI). Useful for debugging.
k3s ctr Run an embedded ctr. This is a CLI for containerd, the container daemon used by K3s. Useful for debugging.
k3s help Shows a list of commands or help for one command

The k3s server and k3s agent commands have additional configuration options that can be viewed with k3s server --help or k3s agent --help.

Registration Options for the K3s Server

For details on configuring the K3s server, refer to the server configuration reference.

Registration Options for the K3s Agent

For details on configuring the K3s agent, refer to the agent configuration reference.

Configuration File

Available as of v1.19.1+k3s1

In addition to configuring K3s with environment variables and CLI arguments, K3s can also use a config file.

By default, values present in a YAML file located at /etc/rancher/k3s/config.yaml will be used on install.

An example of a basic server config file is below:

write-kubeconfig-mode: "0644"
tls-san:
  - "foo.local"
node-label:
  - "foo=bar"
  - "something=amazing"

In general, CLI arguments map to their respective YAML key, with repeatable CLI arguments being represented as YAML lists.

An identical configuration using solely CLI arguments is shown below to demonstrate this:

k3s server \
  --write-kubeconfig-mode "0644"    \
  --tls-san "foo.local"             \
  --node-label "foo=bar"            \
  --node-label "something=amazing"

It is also possible to use both a configuration file and CLI arguments. In these situations, values will be loaded from both sources, but CLI arguments will take precedence. For repeatable arguments such as --node-label, the CLI arguments will overwrite all values in the list.

Finally, the location of the config file can be changed either through the cli argument --config FILE, -c FILE, or the environment variable $K3S_CONFIG_FILE.