DevSpace

Persistent Volumes

Generally, containers are stateless. That means that whenever you write anything to the filesystem of the container, it will be removed when the container restarts.

Altough it is recommend to keep your applications as stateless as possible, sometimes you will need to store data in a directory that should "survive" a container restart, e.g. the data directory within a database container (e.g. /var/lib/mysql for mysql).

Persistent volumes allow you to define a virtual device which is independent of your containers and can be mounted into the containers. An analogy would be a USB stick (persistent volume) that you plug into a computer (container) which always resets the in-build hard drive on every restart.

When you want to persist a folder within a container of one of your components, you need to:

  1. Define a volume within this component
  2. Mount this volume into the container
note

Components require you to specify separete volumes for each component, i.e. the volumes of a component can only be mounted by the containers of the same component.

Define Volumes

DevSpace components allow you to define the following types of Kubernetes volumes:

Persistent Volumes

You can define persistent volumes in the volumes section of each component deployment:

volumes:
- name: nginx
  size: "2Gi"
- name: mysql-data
  size: "5Gi"

The above example defines two volumes, one called nginx with size 2 Gigabyte and one called mysql-data with size 5 Gigabyte.

Show specification for Persistent Volumes
volumes:
- name: [a-z0-9-]{1,253}        # Name of the volume (used to mount the volume)
  size: [number] + Gi|Mi|Ki     # Size of the volume in Gigabyte, Megabyte or Kilobyte

emptyDir Volumes

Using DevSpace components, you can define temporary volumes to share files between containers of a Pod according to Kubernetes EmptyDirVolumeSource specification

volumes:
- name: temp-storage
  emptyDir: {}
Show specification for emptyDir Volumes
volumes:
- name: [a-z0-9-]{1,253}                     # Name of the volume (used to mount the volume)
  emptyDir:                                  # Kubernetes EmptyDirVolumeSource v1
    medium: "" | Memory                      # Default "". The storage medium type
    sizeLimit: nil | [number] + Gi|Mi|Ki     # Default nil. Size of the volume in Gigabyte, Megabyte or Kilobyte
    ...

ConfigMap Volumes

Using DevSpace components, you can define Kubernetes ConfigMaps as volumes according to the Kubernetes ConfigMapVolumeSource specification:

volumes:
- name: nginx-config
  configMap:
    name: my-configmap
Show specification for ConfigMap Volumes
volumes:
- name: [a-z0-9-]{1,253}        # Name of the volume (used to mount the volume)
  configMap:                    # Kubernetes ConfigMapVolumeSource v1
    name: [a-z0-9-]{1,253}      # Name of the ConfigMap
    ...

Secret Volumes

Using DevSpace components, you can define Kubernetes Secrets as volumes according to the Kubernetes SecretVolumeSource specification:

volumes:
- name: secret-token
  secret:
    secretName: my-secret
Show specification for Secret Volumes
volumes:
- name: [a-z0-9-]{1,253}            # Name of the volume (used to mount the volume)
  secret:                           # Kubernetes SecretVolumeSource v1
    secretName: [a-z0-9-]{1,253}    # Name of the Secret
    ...

HostPath Volumes

Using DevSpace components, you can define your Node's filesystem as volumes according to the Kubernetes HostPath specification:

volumes:
- name: docker-sock
  hostPath:
    path: "/var/run/docker.sock"
    type: Socket

The above example will mount your local Docker socket to a socket inside the container, which allows for Docker In Docker (DIND)

Show specification for HostPath volumes
volumes:
- name: [a-z0-9-]{1,253}            # Name of the volume (used to mount the volume)
  hostPath:                         # Kubernetes HostPathVolumeSource v1
    path: [a-z0-9-]{1,253}          # File or Directory on the node's filesystem
    ...

Mount Volumes

After defining a volume for a component, you can mount it in the containers of the same component within the volumeMounts section:

containers:
- image: "dscr.io/username/mysql"
  volumeMounts:
  - containerPath: /var/lib/mysql
    volume:
      name: mysql-data
      subPath: /mysql
      readOnly: false
volumes:
- name: mysql-data
  size: "5Gi"

The example above would create a volume called mysql-data for the component my-component and mount the folder /mysql within this volume into the path /var/lib/mysql within a container of this component. By mounting this volume to /var/lib/mysql, you allow the container to edit the files and folders contained within /var/lib/mysql and restart without losing these changes.

View the specification for volume mounts
containerPath: [path]       # Path within the container
volume:                     # Volume to mount
  name: [volume-name]       # Name of the volume as defined in `volumes` within `chart/values.yaml`
  subPath: [path]           # Path within the volume
  readOnly: false|true      # Detault: false | set to true for read-only mounting

Delete Persistent Volumes

By default, persisent volumes will not be deleted automatically when you remove them from the volumes section of chart/values.yaml. This ensures that persistent data is not being deleted on accident.

To remove a persistent volume, you have to remove it manually with the following commands:

devspace add space [SPACE_NAME]
kubectl delete persistentvolumeclaim [VOLUME_NAME]
Data Loss

Deleting persistent volumes cannot be undone. Your data will be lost forever and cannot be recovered.


FAQ

Can I mount one persistent volume within multiple containers?

Yes, but only if the containers are either in the same component or if at most one of the containers mounts the volume with the readOnly: false option (e.g. one container with readOnly: false and 3 other containers with readOnly: true would work).

Will my persistent volumes be deleted when I re-deploy my application?

Generally: No.

The component chart used to deploy DevSpace components will automatically deploy containers as part of a StatefulSet when you mount any persistent volumes. Kubernetes will not delete these persistent volumes when you delete or update the StatefulSet.

How can I delete everything (including persistent volumes) within a Space?

If you want to force-delete everything (including persistent volumes) within a Space, you can run the following commands:

devspace purge
kubectl delete persistentvolumeclaims --all

Warning: The commands listed above will delete everything within your Space. All your data will be lost forever and cannot be recovered.

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