Mounting Volumes

Article
08/17/2022

Specifying a volume attaches the device(s) to your instance, but does not mount and format the device. If you prefer to have the volumes mounted and formatted when the node is started, set the optional attribute Mount to the name of the mountpoint configuration you wish to use with that volume:

[[[volume reference-data]]]
Size = 100
Mount = data              # The name of the mountpoint to use with this volume

The mountpoint named data is then defined in the configuration section on the node:

[[[configuration cyclecloud.mounts.data]]]
mountpoint = /mount
fs_type = ext4

The above configuration specifies that you are configuring a cyclecloud.mountpoint named data using all volumes which include Mount = data. This volume would be formatted with the ext4 filesystem and would appear at /mount.

Devices

By defining volumes with a mountpoint attribute, the device names will be automatically assigned and used for a given mountpoint. However, you can customize a mountpoint with your own device names. For example:

[[node scheduler]]
  [[[configuration cyclecloud.mounts.data]]]
  mountpoint = /data
  Azure.LUN=0

In Azure, devices are assigned using Logical Unit Numbers (LUN)

In most cases, Azure CycleCloud will automatically assign devices for you. Specifying devices manually is advanced usage, and useful in cases where the image you are using for your node has volumes that will be automatically attached because their attachment was baked into the image. Specifying the devices by hand can also be useful when the ordering of devices has special meaning.

Note

The reserved name boot is used to modify the built-in boot volume.

Advanced Usage

The previous example was a fairly simple: mounting a single, pre-formatted snapshot to a node. However, more advanced mounting can take place, including RAIDing multiple devices together, encrypting, and formatting new filesystems. As an example, the following will describes how to RAID several volumes together and encrypt them before mounting them as a single device on a node:

[[node scheduler]]
....
  [[[volume vol1]]]
  VolumeId = vol-1234abcd
  Mount = giant

  [[[volume vol2]]]
  VolumeId = vol-5678abcd
  Mount = giant

  [[[volume vol3]]]
  VolumeId = vol-abcd1234
  Mount = giant

  [[[configuration cyclecloud.mounts.giant]]]
  mountpoint = /mnt/giant
  fs_type = xfs
  raid_level = 0
  encryption.bits = 256
  encryption.key = "0123456789abcdef9876543210"

The above example shows there are three volumes that should be attached to the node named scheduler, and that their mountpoint is named giant. The configuration for the mountpoint says that these three volumes should be RAIDed together using raid_level = 0 for RAID0, formatted using the xfs filesystem, and the resulting device should be mounted at /mnt/giant. The device should also have block level encryption using 256-bit AES with an encryption key as defined in the template.

Server-Side Encryption with Azure Disk Encryption Sets

CycleCloud supports server-side encryption for OS and data disk Volumes using Azure Disk Encryption Sets. Server-side encryption supports both Platform Managed Keys (the default) and Customer Managed Keys (CMK).

To enable SSE with CMK, you must first set up an Azure Disk Encryption Set and a Key Vault with your key. Follow the documention here to set up your Disk Encryption Set.

Record the ResourceID of the Disk Encryption Set when you create it. If you are using an existing set, then you can find the ResourceID in the Azure Portal in the Disk Encryption Sets blade.

To apply SSE with CMK to your CycleCloud node's Volumes add the following to your [[[volume]]] definition:

Azure.Encryption.Type = EncryptionAtRestWithCustomerKey
Azure.Encryption.DiskEncryptionSetId = /subscriptions/$SUBSCRIPTION-ID/resourceGroups/$RESOURCEGROUPNAME/providers/Microsoft.Compute/diskEncryptionSets/$DISK-ENCRYPTION-SET-NAME

For example:

[[node scheduler]]
....
  [[[volume encryptedVolume]]]
  VolumeId = vol-1234abcd
  Mount = encrypted

  # Insert your RESOURCE ID here:
  Azure.Encryption.DiskEncryptionSetId = /subscriptions/a1234567-1234-1ab2-34c5-a1aab0123456/resourceGroups/myResouceGroup/providers/Microsoft.Compute/diskEncryptionSets/myCMKDiskEncryptionSet
  Azure.Encryption.Type = EncryptionAtRestWithCustomerKey

  [[[configuration cyclecloud.mounts.encrypted]]]
  mountpoint = /mnt/encrypted
  fs_type = ext4
  raid_level = 0

See the Volume Configuration Reference for details.

Mounting Configuration Options

Option	Definition
mountpoint	The place where the device(s) will be mounted after any additional configuration is applied. If a mountpoint is not specified, the name of the mount will be used as part of the mountpoint. For example, if your mount was named ‘data’, the mountpoint would default to ‘/media/data’.
options	Any non-default options to use when mounting the device.
fs_type	The filesystem to use when formatting and/or mounting. Available options are: ext3, ext4, xfs.
size	The size of the filesystem to create when formatting the device(s). Omitting this parameter will use all the space on the device. Size can be specified using M for megabytes (e.g. 150M for 150MB) G for gigabytes (e.g. 200G for 20GB), or percentages (e.g. 100% to use all of the available space).
disabled	If true, the mountpoint will not be created. Useful for quick toggling of mounts for testing and to disable automatic ephemeral mounting. Default: false.
raid_level	The type of RAID configuration to use when multiple devices/volumes are being used. Defaults to a value of 0, meaning RAID0, but other raid levels can be used such as 1 or 10.
raid_device_symlink	When a raid device is created, specifying this attribute will create a symbolic link to the raid device. By default, this attribute is not set and therefore no symlink is created. This should be set in cases where you need access to the underlying raid device.
devices	This is a list of devices that should compose the mountpoint. In general, this parameter shouldn’t need to be specified (as CycleCloud will set this for you based on [[[volume]]] sections), but you can manually specify the devices if so desired.
vg_name	Devices are configured on Linux using the Logical Volume Manager (LVM). The volume group name will be automatically assigned, but in cases where a specific name is used, this attribute can be set. The default is set to `cyclecloud-vgX`, where X is an automatically assigned number.
lv_name	Devices are configured on Linux using the Logical Volume Manager (LVM). This value is automatically assigned and does not need specification, but if you want to use a custom logical volume name, it can be specified using this attribute. Defaults to `lv0`.
order	By specifying an order, you can control the order in which mountpoints are mounted. The default order value for all mountpoints is 1000, except for ‘ephemeral’ which is 0 (ephemeral is always mounted first by default). You can override this behaviour on a case-by-case basis as needed.
encryption.bits	The number of bits to use when encrypting the filesystem. Standard values are `128` or `256` bit AES encryption. This value is required if encryption is desired.
encryption.key	The encryption key to use when encrypting the filesystem. If omitted, a random 2048 bit key will be generated. The automatically generated key is useful for when you are encrypting disks that do not persist between reboots (e.g. encrypting ephemeral devices).
encryption.name	The name of the encrypted filesystem, used when saving encryption keys. Defaults to `cyclecloud_cryptX`, where X is an automatically generated number.
encryption.key_path	The location of the file the key will be written on disk to. Defaults to `/root/cyclecloud_cryptX.key`, where X is a automatically generated number.

Mounting Configuration Defaults

Use these options to set system defaults for mountpoints, which will be used unless otherwise specified:

Options	Definition
cyclecloud.mount_defaults.fs_type	The filesystem type to use for mounts, if not otherwise specified. Default: ext3/ext4 (depending on the platform).
cyclecloud.mount_defaults.size	The default filesystem size to use, if not otherwise specified. Default: 50GB.
cyclecloud.mount_defaults.raid_level	The default raid level to use if multiple devices are assigned to the mountpoint. Default: 0 (RAID0).
cyclecloud.mount_defaults.encryption.bits	The default encryption level unless otherwise specified. Default: undefined.