how docker-registry persist images in openshift origin - docker

Question

i'm new to openshift/kubernetes/docker and i was wondering where the docker registry of openshift origin persist the images , knowing that :
1.in the deployment's yaml of the docker registry , there is only emptyDir volumes declaration
volumes:
- emptyDir: {}
name: registry-storage
2.in the machine where the pod is deployed i can't see no volume using
docker volumes ls
3.the images are still persisted even if i restart the pod
docker registry deployment's yaml :
apiVersion: apps.openshift.io/v1
kind: DeploymentConfig
metadata:
creationTimestamp: '2020-04-26T18:16:50Z'
generation: 1
labels:
docker-registry: default
name: docker-registry
namespace: default
resourceVersion: '1844231'
selfLink: >-
/apis/apps.openshift.io/v1/namespaces/default/deploymentconfigs/docker-registry
uid: 1983153d-87ea-11ea-a4bc-fa163ee581f7
spec:
replicas: 1
revisionHistoryLimit: 10
selector:
docker-registry: default
strategy:
activeDeadlineSeconds: 21600
resources: {}
rollingParams:
intervalSeconds: 1
maxSurge: 25%
maxUnavailable: 25%
timeoutSeconds: 600
updatePeriodSeconds: 1
type: Rolling
template:
metadata:
creationTimestamp: null
labels:
docker-registry: default
spec:
containers:
- env:
- name: REGISTRY_HTTP_ADDR
value: ':5000'
- name: REGISTRY_HTTP_NET
value: tcp
- name: REGISTRY_HTTP_SECRET
value:
- name: REGISTRY_MIDDLEWARE_REPOSITORY_OPENSHIFT_ENFORCEQUOTA
value: 'false'
- name: OPENSHIFT_DEFAULT_REGISTRY
value: 'docker-registry.default.svc:5000'
- name: REGISTRY_HTTP_TLS_CERTIFICATE
value: /etc/secrets/registry.crt
- name: REGISTRY_OPENSHIFT_SERVER_ADDR
value: 'docker-registry.default.svc:5000'
- name: REGISTRY_HTTP_TLS_KEY
value: /etc/secrets/registry.key
image: 'docker.io/openshift/origin-docker-registry:v3.11'
imagePullPolicy: IfNotPresent
livenessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 5000
scheme: HTTPS
initialDelaySeconds: 10
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
name: registry
ports:
- containerPort: 5000
protocol: TCP
readinessProbe:
failureThreshold: 3
httpGet:
path: /healthz
port: 5000
scheme: HTTPS
periodSeconds: 10
successThreshold: 1
timeoutSeconds: 5
resources:
requests:
cpu: 100m
memory: 256Mi
securityContext:
privileged: false
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /registry
name: registry-storage
- mountPath: /etc/secrets
name: registry-certificates
dnsPolicy: ClusterFirst
nodeSelector:
node-role.kubernetes.io/infra: 'true'
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
serviceAccount: registry
serviceAccountName: registry
terminationGracePeriodSeconds: 30
volumes:
- emptyDir: {}
name: registry-storage
- name: registry-certificates
secret:
defaultMode: 420
secretName: registry-certificates
test: false
triggers:
- type: ConfigChange
status:
availableReplicas: 1
conditions:
- lastTransitionTime: '2020-04-26T18:17:12Z'
lastUpdateTime: '2020-04-26T18:17:12Z'
message: replication controller "docker-registry-1" successfully rolled out
reason: NewReplicationControllerAvailable
status: 'True'
type: Progressing
- lastTransitionTime: '2020-05-05T09:39:57Z'
lastUpdateTime: '2020-05-05T09:39:57Z'
message: Deployment config has minimum availability.
status: 'True'
type: Available
details:
causes:
- type: ConfigChange
message: config change
latestVersion: 1
observedGeneration: 1
readyReplicas: 1
replicas: 1
unavailableReplicas: 0
updatedReplicas: 1
to restart : i just delete the pod and a new one is created since i'm using a deployment
i'm creating the file in the /registry

Answer 1

Restarting does not mean the data is deleted, it still exist in the container top layer, suggest you get started by reading this.
Persistence is, for example in Kubernetes, when a pod is deleted and re-created on another node and still maintains the same state of a volume.