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Customizing Ephemeral Drive Mounting and Configuration via Cloud-Init

Ephemeral drives provide temporary storage for active workloads during a VM’s runtime. The mounting behavior of ephemeral drives can be customized at the time of VM creation by passing a cloud-init configuration file. This guide covers different ways to handle ephemeral drives using cloud-init, including mounting to custom locations, changing the filesystem format, or disabling the mount entirely. For more details on ephemeral storage, see this article.

Mounting ephemeral drive to a custom location​

By default, ephemeral drives are mounted under /ephemeral. To mount them elsewhere follow these steps:

  1. Navigate to the Deploy a new virtual machine page in the Hyperstack console.

  2. Set up your VM with the desired specifications, then scroll to the bottom of the page and click Configure Additional Settings.

  3. In the Cloud-init Script section, select YAML syntax format. Then, paste the following cloud-init configuration, replacing /your/custom/path to any directory path where you'd like to mount the ephemeral drive (e.g. /var/opt):

    #cloud-config

    mounts:
      - [ephemeral0, /your/custom/path]

  4. Deploy your VM and the ephemeral drive will be mounted to the custom directory during creation.

Changing filesystem format and mount location​

To format the ephemeral drive with a different filesystem (e.g., xfs) and mount it to a custom location (e.g., /data), follow the steps outlined here but modify the configuration file as follows:

#cloud-config

disk_setup:
  ephemeral0:
    table_type: "gpt"
    layout: true
    overwrite: True

fs_setup:
  - label: ephemeral0
    filesystem: xfs
    device: "ephemeral0"
    partition: "auto"
    overwrite: True

mounts:
  - [ephemeral0, /data, xfs]

This mounts the ephemeral drive under /data and uses the xfs filesystem.

Choosing not to mount the ephemeral drive​

To prevent the ephemeral drive from being mounted, follow the steps outlined in Hyperstack here but modify the configuration file as follows:

#cloud-config

mounts:
  - [ephemeral0, null]

Using the API to manage ephemeral mounting​

  1. Save your cloud-init configuration content, as defined in the examples above, in a file (e.g., user-data.txt). You can also use a bash script, as shown in the example below.

    cat << EOF > user_data.txt
    #cloud-config

    disk_setup:
      ephemeral0:
        table_type: "gpt"
        layout: true
        overwrite: True

    fs_setup:
      - label: ephemeral0
        filesystem: xfs
        device: "ephemeral0"
        partition: "auto"
        overwrite: True

    mounts:
      - [ephemeral0, /data, xfs]
    EOF

  2. Use the file in the user_data field of the Create Virtual Machine API request. You can refer to the API documentation for details on how to automate VM creation with this configuration. See an example API call below.

    # First convert the user data to a single line JSON string
    user_data_content=$(jq -Rs '.' < user_data.txt)

    # Then use the API to create a VM with the user data
    curl --location 'https://infrahub-api.nexgencloud.com/v1/core/virtual-machines' \
    --header 'Content-Type: application/json' \
    --header "api_key: $HYPERSTACK_API_KEY" \
    --data '{
        "name": "ephemeral-mount-example",
        "environment_name": "default-CANADA-1",
        "image_name": "Ubuntu Server 22.04 LTS R550 CUDA 12.4 with Docker",
        "flavor_name": "n3-A100x1",
        "key_name": "default-CANADA-1-key",
        "count": 1,
        "assign_floating_ip": true,
        "user_data": '"$user_data_content"'
    }'

  3. Check the mount location and filesystem format of the ephemeral drive on the VM after creation.

lsblk -f

Below is an example of the expected output (output may vary slightly based on the configuration):

NAME FSTYPE FSVER LABEL      UUID                                 FSAVAIL FSUSE% MOUNTPOINTS
[.. truncated ..]
vdb
└─vdb1
     xfs          ephemeral0 aefb82e5-f27c-4b33-9d58-b65eb32ffd35  744.4G     1% /data