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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
demothroughout this tutorial.$ kubectl create ns demo namespace/demo created $ kubectl get ns demo NAME STATUS AGE 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.
Overview
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 [mysqld] max_connections = 200 read_buffer_size = 1048576 EOF $ cat my-config.cnf [mysqld] 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 data: my-config.cnf: W215c3FsZF0KbWF4X2Nvbm5lY3Rpb25zID0gMjAwCnJlYWRfYnVmZmVyX3NpemUgPSAxMDQ4NTc2Cg== kind: Secret metadata: 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 https://github.com/kubedb/docs/raw/v2025.6.30/docs/guides/mysql/configuration/config-file/yamls/mysql-custom.yaml mysql.kubedb.com/custom-mysql created Below is the YAML for the MySQL crd we just created.
apiVersion: kubedb.com/v1 kind: MySQL metadata: name: custom-mysql namespace: demo spec: version: "9.1.0" configSecret: name: my-configuration storage: storageClassName: "standard" accessModes: - ReadWriteOnce resources: requests: storage: 1Gi Now, wait a few minutes. KubeDB operator will create necessary PVC, petset, 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 petset’s pod is running
$ kubectl get pod -n demo NAME READY STATUS RESTARTS AGE 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 9.1.0-1debian10 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 9.1.0) 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: 9.1.0). 2022-06-28T13:22:24.495121Z 0 [System] [MY-010910] [Server] /usr/sbin/mysqld: Shutdown complete (mysqld 9.1.0) 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: '9.1.0' 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 https://github.com/kubedb/docs/raw/v2025.6.30/docs/guides/mysql/configuration/config-file/yamls/phpmyadmin.yaml 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' 30942 $ kubectl get node -o json | jq '.items[].status.addresses[].address' "172.18.0.3" "kind-control-plane" "172.18.0.4" "kind-worker" "172.18.0.2" "kind-worker2" # expected url will be: url: http://172.18.0.4:30942 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 hostIP: 10.0.2.15 podIP: 172.17.0.6 $ kubectl get secrets -n demo custom-mysql-auth -o jsonpath='{.data.\user}' | base64 -d root $ kubectl get secrets -n demo custom-mysql-auth -o jsonpath='{.data.\password}' | base64 -d MLO5_fPVKcqPiEu9 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. 
Cleaning up
To cleanup the Kubernetes resources created by this tutorial, run:
kubectl patch -n demo my/custom-mysql -p '{"spec":{"deletionPolicy":"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
- Quickstart MySQL with KubeDB Operator.
- Initialize MySQL with Script.
- Monitor your MySQL database with KubeDB using out-of-the-box Prometheus operator.
- Monitor your MySQL database with KubeDB using out-of-the-box builtin-Prometheus.
- Use private Docker registry to deploy MySQL with KubeDB.
- Use kubedb cli to manage databases like kubectl for Kubernetes.
- Detail concepts of MySQL object.
- Want to hack on KubeDB? Check our contribution guidelines.