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Using Custom Configuration File

KubeDB supports providing custom configuration for MySQL. This tutorial will show you how to use KubeDB to run a MySQL database with custom configuration.

Before You Begin

  • At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.

  • Now, install KubeDB cli on your workstation and KubeDB operator in your cluster following the steps here.

  • To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.

    $ kubectl create ns demo
    namespace/demo created
    $ kubectl get ns demo
    demo    Active  5s

Note: YAML files used in this tutorial are stored in docs/guides/mysql/configuration/config-file/yamls folder in GitHub repository kubedb/docs.


MySQL allows to configure database via configuration file. The default configuration for MySQL can be found in /etc/mysql/my.cnf file. When MySQL starts, it will look for custom configuration file in /etc/mysql/conf.d directory. If configuration file exist, MySQL instance will use combined startup setting from both /etc/mysql/my.cnf and *.cnf files in /etc/mysql/conf.d directory. This custom configuration will overwrite the existing default one. To know more about configuring MySQL see here.

At first, you have to create a config file with .cnf extension with your desired configuration. Then you have to put this file into a volume. You have to specify this volume in spec.configSecret section while creating MySQL crd. KubeDB will mount this volume into /etc/mysql/conf.d directory of the database pod.

In this tutorial, we will configure max_connections and read_buffer_size via a custom config file. We will use configMap as volume source.

Custom Configuration

At first, let’s create my-config.cnf file setting max_connections and read_buffer_size parameters.

cat <<EOF > my-config.cnf
max_connections = 200
read_buffer_size = 1048576

$ cat my-config.cnf
max_connections = 200
read_buffer_size = 1048576

Here, read_buffer_size is set to 1MB in bytes.

Now, create a secret with this configuration file.

$ kubectl create secret generic -n demo my-configuration --from-file=./my-config.cnf
configmap/my-configuration created

Verify the secret has the configuration file.

$ kubectl get secret -n demo my-configuration -o yaml
apiVersion: v1
  my-config.cnf: W215c3FsZF0KbWF4X2Nvbm5lY3Rpb25zID0gMjAwCnJlYWRfYnVmZmVyX3NpemUgPSAxMDQ4NTc2Cg==
kind: Secret
  creationTimestamp: "2022-06-28T13:20:42Z"
  name: my-configuration
  namespace: demo
  resourceVersion: "1601408"
  uid: 82e1a722-d80f-448e-89b5-c64de81ed262
type: Opaque

Now, create MySQL crd specifying spec.configSecret field.

$ kubectl apply -f created

Below is the YAML for the MySQL crd we just created.

kind: MySQL
  name: custom-mysql
  namespace: demo
  version: "8.0.29"
    name: my-configuration
    storageClassName: "standard"
    - ReadWriteOnce
        storage: 1Gi

Now, wait a few minutes. KubeDB operator will create necessary PVC, statefulset, services, secret etc. If everything goes well, we will see that a pod with the name custom-mysql-0 has been created.

Check that the statefulset’s pod is running

$ kubectl get pod -n demo
custom-mysql-0   1/1       Running   0          44s

Check the pod’s log to see if the database is ready

$ kubectl logs -f -n demo custom-mysql-0
2022-06-28 13:22:10+00:00 [Note] [Entrypoint]: Entrypoint script for MySQL Server 8.0.29-1debian10 started.
2022-06-28 13:22:10+00:00 [Note] [Entrypoint]: Switching to dedicated user 'mysql'

2022-06-28 13:22:20+00:00 [Note] [Entrypoint]: Database files initialized
2022-06-28 13:22:20+00:00 [Note] [Entrypoint]: Starting temporary server
2022-06-28T13:22:20.233556Z 0 [System] [MY-010116] [Server] /usr/sbin/mysqld (mysqld 8.0.29) starting as process 92
2022-06-28T13:22:20.252075Z 1 [System] [MY-013576] [InnoDB] InnoDB initialization has started.
2022-06-28T13:22:20.543772Z 1 [System] [MY-013577] [InnoDB] InnoDB initialization has ended.
2022-06-28 13:22:22+00:00 [Note] [Entrypoint]: Stopping temporary server
2022-06-28T13:22:22.354537Z 10 [System] [MY-013172] [Server] Received SHUTDOWN from user root. Shutting down mysqld (Version: 8.0.29).
2022-06-28T13:22:24.495121Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 8.0.29)  MySQL Community Server - GPL.
2022-06-28 13:22:25+00:00 [Note] [Entrypoint]: Temporary server stopped

2022-06-28 13:22:25+00:00 [Note] [Entrypoint]: MySQL init process done. Ready for start up.

2022-06-28T13:22:26.064259Z 0 [Warning] [MY-011810] [Server] Insecure configuration for --pid-file: Location '/var/run/mysqld' in the path is accessible to all OS users. Consider choosing a different directory.
2022-06-28T13:22:26.076352Z 0 [System] [MY-011323] [Server] X Plugin ready for connections. Bind-address: '::' port: 33060, socket: /var/run/mysqld/mysqlx.sock
2022-06-28T13:22:26.076407Z 0 [System] [MY-010931] [Server] /usr/sbin/mysqld: ready for connections. Version: '8.0.29'  socket: '/var/run/mysqld/mysqld.sock'  port: 3306  MySQL Community Server - GPL.


Once we see [Note] /usr/sbin/mysqld: ready for connections. in the log, the database is ready.

Now, we will check if the database has started with the custom configuration we have provided.

First, deploy phpMyAdmin to connect with the MySQL database we have just created.

 $ kubectl create -f
deployment.extensions/myadmin created
service/myadmin created

Then, open your browser and go to the following URL: http://{node-ip}:{myadmin-svc-nodeport}. For kind cluster, you can get this URL by running the following command:

$ kubectl get svc -n demo myadmin -o json | jq '.spec.ports[].nodePort'

$ kubectl get node -o json | jq '.items[].status.addresses[].address'

# expected url will be:

Now, let’s connect to the database from the phpMyAdmin dashboard using the database pod IP and MySQL user password.

$ kubectl get pods custom-mysql-0 -n demo -o yaml | grep IP

$ kubectl get secrets -n demo custom-mysql-auth -o jsonpath='{.data.\user}' | base64 -d

$ kubectl get secrets -n demo custom-mysql-auth -o jsonpath='{.data.\password}' | base64 -d

Once, you have connected to the database with phpMyAdmin go to Variables tab and search for max_connections and read_buffer_size. Here are some screenshot showing those configured variables. max_connections


Cleaning up

To cleanup the Kubernetes resources created by this tutorial, run:

kubectl patch -n demo my/custom-mysql -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
kubectl delete -n demo my/custom-mysql

kubectl delete deployment -n demo myadmin
kubectl delete service -n demo myadmin

kubectl delete ns demo

If you would like to uninstall KubeDB operator, please follow the steps here.

Next Steps