Help Center/ Cloud Container Engine_Autopilot/ User Guide/ Storage/ emptyDir
Updated on 2025-02-27 GMT+08:00
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emptyDir

An emptyDir volume provides ephemeral storage for pods. Its lifecycle is the same as that of a pod. Memory can be specified as the storage medium. When the pod is deleted, the emptyDir volume is deleted, and the data is lost.

Using the Console to Use a Temporary Path

  1. Log in to the CCE console and click the cluster name to access the cluster console.
  2. In the navigation pane on the left, choose Workloads. Then click the Deployments tab.
  3. In the upper right corner, click Create Workload. On the displayed page, click Data Storage in the Container Settings area and click Add Volume to select emptyDir.

    Table 1 describes the parameters for mounting the volume. For details about other parameters, see Creating a Workload.
    Table 1 Parameters for mounting an emptyDir volume

    Parameter

    Description

    Storage Medium
    Memory:
    • You can select this option to improve the running speed, but the storage capacity is subject to the memory size. This option is suitable when data volume is small and efficient read and write is required.
    • If this option is not selected, data is stored in local disks. This fits to the scenarios where a large amount of data needs to be stored but read/write efficiency is not high.
    NOTE:
    • If Memory is selected, pay attention to the memory size. If the storage capacity exceeds the memory size, OOM will occur.
    • If Memory is selected, the size of an emptyDir volume is the same as the pod specifications.
    • If Memory is not selected, emptyDir volumes will not occupy the system memory.

    Mount Path

    Enter a mount path, for example, /tmp.

    This parameter indicates the container path that the volume will be mounted to. Do not mount the volume to a system directory such as / or /var/run. This may cause container errors. Mount the volume to an empty directory. If the directory is not empty, ensure that there are no files that affect container startup. If there are such files, they will be replaced, which will lead to a container startup or workload creation failure.
    NOTICE:

    If a volume is mounted to a high-risk directory, use an account with minimum permissions to start the container, or high-risk files on the host may be damaged.

    Subpath

    Enter the subpath of the storage volume and mount a path in the storage volume to the container. In this way, different folders of the same storage volume can be used in a single pod. Enter a subpath, for example, tmp, indicating that data in the mount path of the container is stored in the tmp directory of the storage volume. If this parameter is left blank, the root path is used by default.

    Permission
    • Read-only: You can only read the data in the mounted volume.
    • Read-write: You can modify the volume mounted to the path. Newly written data will not be migrated if the container is migrated, which may cause data loss.

  4. Configure other parameters and click Create Workload.

Using kubectl to Use a Temporary Path

  1. Use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
  2. Create a file named nginx-emptydir.yaml and edit it.

    vi nginx-emptydir.yaml

    The content of the YAML file is as follows:

    apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-emptydir
  namespace: default
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx-emptydir
  template:
    metadata:
      labels:
        app: nginx-emptydir
    spec:
      containers:
        - name: container-1
          image: nginx:latest
          volumeMounts:
            - name: vol-emptydir     # Volume name, which must be the same as the volume name in the volumes field.
              mountPath: /tmp        # Path to which an emptyDir volume is mounted.
      imagePullSecrets:
        - name: default-secret
      volumes:
        - name: vol-emptydir         # Volume name, which can be customized.
          emptyDir:
            medium: Memory          # emptyDir volume medium: If this parameter is set to Memory, the memory is enabled. If this parameter is left blank, the native default storage medium is used.
            sizeLimit: 1Gi          # Volume capacity.

  3. Create a workload.

    kubectl apply -f nginx-emptydir.yaml

Parent Topic: Storage