First, we need to create ConfigMap and Headless Service. 
Both are needed for init and regular containers. 
ConfigMap defines MySQL master/replica configfiles.
Headless Service defines static DNS A record (internal for k8s).
Note: this is example from kubernetes (on google cloud), adjusted here to work on OCI. 

- Create ConfiMap
------------------

 $ kubectl create -f mysql-configmap.yml
 $ kubectl describe cm mysql

Note: 
'kubectl create cm cm-name --from-file=yml-file' may not work well. 
It creates cm, but format diff from 'create -f' and it's not read by init-mysql. 

- Create headless service
---------------------------

 $ kubectl create -f mysql-service.yml
 $ kubectl describe service/mysql
 $ kubectl describe service/mysql-read 

- Review OCI storageClass, will be used for dynamic provisioning of OCI block volumes
------------------------------------------------------------------------------------

 $ kubectl get storageclass
 NAME            PROVISIONER                       RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
 oci (default)   oracle.com/oci                    Delete          Immediate              false                  253d
 oci-bv          blockvolume.csi.oraclecloud.com   Delete          WaitForFirstConsumer   false                  106d

- Create StatefulSet
----------------------

 $ kubectl create -f statefulset-mysql.yml
 $ kubectl get all,pv,pvc
 $ kubectl describe pod/mysql-0  

Pods and PVC have unique name, like pod/mysql-0 and persistentvolumeclaim/data-mysql-0.
PV is dynamic so name is like persistentvolume/csi-796b7b71-a23a-4400-aa0c-17289636bfa9.

- Scaling statefulSet
----------------------

 $ kubectl scale --replicas=3 statefulset.apps/mysql

- Troubleshoot
-------------------

- Logs from container:

 $ kubectl describe <pod-name>
 $ kubectl logs <pod-name> -c <container-name>

 examples:
 $ kubectl logs pod/mysql-0 -c init-mysql
 $ kubectl logs pod/mysql-0 -c clone-mysql
 $ kubectl logs pod/mysql-0 -c mysql
 $ kubectl logs pod/mysql-0 -c xtrabackup

- Enter a container, and examine it. 
---------------------------------------

 Syntax: kubectl exec -it pod/<pod-name> -c <container-name> -- bash
 $ kubectl exec -it pod/mysql-0 -c mysql -- bash

Example, examining container mysql:

root@mysql-0:/etc# cat /etc/debian_version
10.6

root@mysql-0:/etc# hostname
mysql-0

root@mysql-0:/# cat /etc/hosts
# Kubernetes-managed hosts file.
10.x.x.239    mysql-0.mysql.default.svc.cluster.local mysql-0

root@mysql-0:/etc# mysql
Server version: 5.7.32-log MySQL Community Server (GPL)
mysql> show databases;
+------------------------+
| Database               |
+------------------------+
| information_schema     |
| mysql                  |
| performance_schema     |
| sys                    |
| xtrabackup_backupfiles |
+------------------------+
5 rows in set (0.00 sec)

root@mysql-0:/etc# lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0 46.6G  0 disk
|-sda1   8:1    0  200M  0 part
|-sda2   8:2    0    8G  0 part
`-sda3   8:3    0 38.4G  0 part /etc/mysql/conf.d
sdb      8:16   0   50G  0 disk /var/lib/mysql

- Updating StatefulSet
--------------------------

- Edit statefulset, this command opens the editor (vi), 
  change image, like from 5.7.31 to 5.7 (tag for 5.7.32),
  all these images are in OCIR. 

 $ kubectl edit statefulset.apps/mysql
   statefulset.apps/mysql edited

- Follow rollout, pod with highest number will be updated first. 

 $ kubectl get pods
  NAME          READY   STATUS        RESTARTS   AGE
  pod/mysql-0   2/2     Running       0          6m56s
  pod/mysql-1   2/2     Terminating   0          5m33s

- Then all other pods will be updated. 

 $ kubectl get pods
  NAME      READY   STATUS        RESTARTS   AGE
  mysql-0   1/2     Terminating   0          7m44s
  mysql-1   2/2     Running       0          35s

- MySQL version now is 5.7.32, verify via mysqlclient pod or entering mysql container.