The ability to run Kubernetes using a datastore other than etcd sets K3s apart from other Kubernetes distributions. This feature provides flexibility to Kubernetes operators. The available datastore options allow you to select a datastore that best fits your use case. For example:

• If your team doesn’t have expertise in operating etcd, you can choose an enterprise-grade SQL database like MySQL or PostgreSQL
• If you need to run a simple, short-lived cluster in your CI/CD environment, you can use the embedded SQLite database

• If you wish to deploy Kubernetes on the edge and require a highly available solution but can’t afford the operational overhead of managing a database at the edge, you can use K3s’s embedded HA datastore built on top of DQLite (currently experimental)K3s supports the following datastore options:

• Embedded SQLite

• PostgreSQL (certified against versions 10.7 and 11.5)
• MySQL (certified against version 5.7)
• etcd (certified against version 3.3.15)
• Embedded DQLite for High Availability (experimental)

External Datastore Configuration Parameters

If you wish to use an external datastore such as PostgreSQL, MySQL, or etcd you must set the datastore-endpoint parameter so that K3s knows how to connect to it. You may also specify parameters to configure the authentication and encryption of the connection. The below table summarizes these parameters, which can be passed as either CLI flags or environment variables.

As a best practice we recommend setting these parameters as environment variables rather than command line arguments so that your database credentials or other sensitive information aren’t exposed as part of the process info.

Datastore Endpoint Format and Functionality

As mentioned, the format of the value passed to the datastore-endpoint parameter is dependent upon the datastore backend. The following details this format and functionality for each supported external datastore.

In its most common form, the datastore-endpoint parameter for PostgreSQL has the following format:

postgres://username:password@hostname:port/database-name

More advanced configuration parameters are available. For more information on these, please see https://godoc.org/github.com/lib/pq.

If you specify a database name and it does not exist, the server will attempt to create it.

If you only supply postgres:// as the endpoint, K3s will attempt to do the following:

• Connect to localhost using postgres as the username and password
• Create a database named kubernetes

In its most common form, the datastore-endpoint parameter for MySQL has the following format:

mysql://username:password@tcp(hostname:3306)/database-name

More advanced configuration parameters are available. For more information on these, please see https://github.com/go-sql-driver/mysql#dsn-data-source-name

Note that due to a known issue in K3s, you cannot set the tls parameter. TLS communication is supported, but you cannot, for example, set this parameter to “skip-verify” to cause K3s to skip certificate verification.

If you specify a database name and it does not exist, the server will attempt to create it.

If you only supply mysql:// as the endpoint, K3s will attempt to do the following:

• Connect to the MySQL socket at /var/run/mysqld/mysqld.sock using the root user and no password
• Create a database with the name kubernetes

In its most common form, the datastore-endpoint parameter for etcd has the following format:

https://etcd-host-1:2379,https://etcd-host-2:2379,https://etcd-host-3:2379

The above assumes a typical three node etcd cluster. The parameter can accept one more comma separated etcd URLs.

Based on the above, the following example command could be used to launch a server instance that connects to a PostgresSQL database named k3s-db:

K3S_DATASTORE_ENDPOINT='postgres://username:password@hostname:5432/k3s-db' k3s server

And the following example could be used to connect to a MySQL database using client certificate authentication:

K3S_DATASTORE_ENDPOINT='mysql://username:password@tcp(hostname:3306)/k3s-db' \
K3S_DATASTORE_CERTFILE='/path/to/client.crt' \
K3S_DATASTORE_KEYFILE='/path/to/client.key' \
k3s server

Embedded DQLite for HA (Experimental)

K3s’s use of DQLite is similar to its use of SQLite. It is simple to setup and manage. As such, there is no external configuration or additional steps to take in order to use this option. Please see High Availability with Embedded DB (Experimental) for instructions on how to run with this option.