Mount an EmptyDir volume on an ECI instance - Elastic Container Instance

Usage notes

An emptyDir volume provides temporary storage. Data in an emptyDir volume is permanently deleted if the ECI instance is deleted or restarted.

Configuration (API)

When you call the CreateContainerGroup API operation to create an elastic container instance, you can use Volume-related parameters to specify volumes, and then use Container.VolumeMount-related parameters to mount the volumes to containers. The relevant parameters are described below. For more information, see CreateContainerGroup.

Declare a volume

When you use Volume-related parameters to specify volumes, you must first specify the types and names of the volumes. Then, you must configure other Volume-related parameters based on the value of the Volume.N.Type parameter.

Parameter	Type	Example	Description
Volume.N.Name	String	emptydir-demo	The name of the volume.
Volume.N.Type	String	EmptyDirVolume	Specifies the volume type. Set to `EmptyDirVolume` to declare an emptyDir volume.
Volume.N.EmptyDirVolume.Medium	String	Memory	The storage medium for the emptyDir volume. If you leave this parameter empty, the host's file system is used by default. Valid values: `Memory`: The volume is stored in memory. `LocalRaid0`: The local disks are combined into a RAID 0 array. This value is applicable only when you create an instance that has local disks mounted. For more information, see Specify local disk specifications to create an instance.
Volume.N.EmptyDirVolume.SizeLimit	String	256Mi	The size of the emptyDir volume. You must include a unit in the value, such as `Gi` or `Mi`.

Note

For an emptyDir volume with Medium set to Memory, you can set SizeLimit to modify the shm size of the instance. After you set the Medium and SizeLimit parameters, you must mount the emptyDir volume to the /dev/shm directory of the container.

Mount volumes

After you specify volumes, you can use VolumeMount-related parameters to mount the volumes to containers.

Parameter	Type	Example	Description
Container.N.VolumeMount.N.Name	String	test-volume	The name of volume N to be mounted to container N. This value is the value of Volume.N.Name.
Container.N.VolumeMount.N.MountPath	String	/usr/share	The path within the container at which to mount the volume. Data in this directory is obscured by the data on the volume.
Container.N.VolumeMount.N.SubPath	String	/usr/sub	The subdirectory of the volume. This parameter specifies different subdirectories of the same volume that the instance can mount to different subdirectories of containers.
Container.N.VolumeMount.N.ReadOnly	Boolean	false	Specifies whether the mount directory is read-only. Default value: false.
Container.N.VolumeMount.N.MountPropagation	String	None	The mount propagation setting of volume N. Mount propagation allows you to share volumes that are mounted to one container to other containers in the same elastic container instance, or even to other elastic container instances on the same host. Valid values: None: The volume mount does not receive subsequent mounts that are mounted to this volume or its subdirectories. HostToContainer: The volume mount receives all subsequent mounts that are mounted to this volume or its subdirectories. Bidirectional: This value has a similar effect as HostToContainer. The volume mount receives all subsequent mounts that are mounted to this volume or its subdirectories. In addition, all volume mounts created by container N are propagated back to the host and to all containers of all elastic container instances that use the same volume. Default value: None.

Note

Volumes can also be mounted to init containers. The required parameters are similar to the parameters in the preceding table. You only need to change Container to InitContainer.

Configuration (console)

When you create an elastic container instance on the Elastic Container Instance buy page, you can specify volumes in the Container Group Configurations section and then mount the volumes to containers in the Container Configurations section.

Declare a volume

In the Container Group Configurations section, expand Advanced Settings.
On the Temporary Directories tab of the Storage section, click Add.
Enter a name for the emptyDir volume.

For example, enter emptydir-demo in the Name field.

Mount a volume

In the Container Configurations section, select a container and expand its advanced settings.
Turn on the Storage switch and click Add.

You can add only the volumes that you declared when you configured the container group.

Select the storage with the name emptydir-demo and type Temporary Directories, and set the mount path in the container to /data.

Note

If you want to mount volumes to multiple containers, select more containers and repeat the preceding operations.

Examples

The following examples show the parameters for calling the CreateContainerGroup operation to create an ECI instance and mount an emptyDir volume to the instance. For more information, see CreateContainerGroup.

Example 1: Share data between containers

ContainerGroupName=test-emptydir
# Declare a volume
Volume.1.Name=emptydir-demo
Volume.1.Type=EmptyDirVolume
# Mount the volume to container 1
Container.1.Name=nginx
Container.1.Image=registry-vpc.cn-hangzhou.aliyuncs.com/eci_open/nginx:1.14.2
Container.1.VolumeMount.1.Name=emptydir-demo
Container.1.VolumeMount.1.MountPath=/data1
# Mount the volume to container 2
Container.2.Name=busybox
Container.2.Image=registry-vpc.cn-hangzhou.aliyuncs.com/eci_open/busybox:1.30
Container.2.Command.1=sleep
Container.2.Arg.1=999999
Container.2.VolumeMount.1.Name=emptydir-demo
Container.2.VolumeMount.1.MountPath=/data2

In this example, Container 1 and Container 2 share an emptyDir volume. The /data1 directory in Container 1 and the /data2 directory in Container 2 are initially empty. Any files that you add to the emptyDir volume from one container can be accessed by the other container.

Example 2: Modify the shm size of an instance

ContainerGroupName=test-emptydir
# Declare a volume
Volume.1.Name=emptydir-shm
Volume.1.Type=EmptyDirVolume
Volume.1.EmptyDirVolume.Medium=Memory
Volume.1.EmptyDirVolume.SizeLimit=256Mi
# Mount the volume to container 1
Container.1.Name=nginx
Container.1.Image=registry-vpc.cn-hangzhou.aliyuncs.com/eci_open/nginx:1.14.2
Container.1.VolumeMount.1.Name=emptydir-shm
Container.1.VolumeMount.1.MountPath=/dev/shm

In this example, setting EmptyDirVolume.Medium to Memory and EmptyDirVolume.SizeLimit to 256Mi, and then mounting the emptyDir volume to the /dev/shm directory, changes the shm size of the ECI instance to 256 MiB.