Create a DB backup from a pod running MySQL on Kubernetes

When using the MySQL docker image you can easily create a DB dump with this one-line CLI command.

kubectl exec -ti \
  $(kubectl get pod -l app=mysql -o name) -- \
  sh -c 'mysqldump -u$MYSQL_USER -p$MYSQL_PASSWORD $MYSQL_DATABASE 2>/dev/null' \
  > database-`date -I`.sql

This assumes the pod running MySQL has a label app=mysql. A file named database-YYYY-MM-DD.sql will be created with the DB contents.

Because the mysqldump command is wrapped in sh it will use the environment variables from the container so you don't have to enter the password manually.