Type: disk - Incus documentation
Description: Disk devices supply additional storage to instances. For containers, they are essentially mount points inside the instance (either as a bind-mount of an existing file or directory on the host, or, ...

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# Type: `disk`

Note

The `disk` device type is supported for both containers and VMs. It supports hotplugging for both containers and VMs.

Disk devices supply additional storage to instances.

For containers, they are essentially mount points inside the instance (either as a bind-mount of an existing file or directory on the host, or, if the source is a block device, a regular mount). Virtual machines share host-side mounts or directories through `9p` or `virtiofs` (if available), or as VirtIO disks for block-based disks.

Warning

The device name affects the serial generated for the device. If the device name exceeds 14 characters for `nvme` and `virtio-blk`, or 30 characters for `virtio-scsi`, Incus will hash the device value to ensure the generated serial remains within supported length constraints. The device name itself is left unchanged.

## Types of disk devices

You can create disk devices from different sources. The value that you specify for the `source` option specifies the type of disk device that is added:

Storage volume

  The most common type of disk device is a storage volume. To add a storage volume, specify its name as the `source` of the device:

      incus config device add <instance_name> <device_name> disk pool=<pool_name> source=<volume_name> [path=<path_in_instance>]

  The path is required for file system volumes, but not for block volumes.

  Alternatively, you can use the `incus storage volume attach` command to Attach the volume to an instance. Both commands use the same mechanism to add a storage volume as a disk device.

  It’s possible to attach a sub-path of a custom volume to an instance using the `source=<volume_name>/<sub_path>` syntax. If the sub-path doesn’t exist inside the custom volume, it will be created automatically when the device is started. When new directories are created this way, the `device-disk-device-conf:initial.uid`, `device-disk-device-conf:initial.gid` and `device-disk-device-conf:initial.mode` options are used to set their ownership and permissions (defaulting to `0`, `0` and `0711` respectively).

Path on the host

  You can share a path on your host (either a file system or a block device) to your instance by adding it as a disk device with the host path as the `source`:

      incus config device add <instance_name> <device_name> disk source=<path_on_host> [path=<path_in_instance>]

  The path is required for file systems, but not for block devices.

Ceph RBD

  Incus can use Ceph to manage an internal file system for the instance, but if you have an existing, externally managed Ceph RBD that you would like to use for an instance, you can add it with the following command:

      incus config device add <instance_name> <device_name> disk source=ceph:<pool_name>/<volume_name> ceph.user_name=<user_name> ceph.cluster_name=<cluster_name> [path=<path_in_instance>]

  The path is required for file systems, but not for block devices.

CephFS

  Incus can use Ceph to manage an internal file system for the instance, but if you have an existing, externally managed Ceph file system that you would like to use for an instance, you can add it with the following command:

      incus config device add <instance_name> <device_name> disk source=cephfs:<fs_name>/<path> ceph.user_name=<user_name> ceph.cluster_name=<cluster_name> path=<path_in_instance>

ISO file

  You can add an ISO file as a disk device for a virtual machine. It is added as a ROM device inside the VM.

  This source type is applicable only to VMs.

  To add an ISO file, specify its file path as the `source`:

      incus config device add <instance_name> <device_name> disk source=<file_path_on_host>

VM `cloud-init`

  You can generate a `cloud-init` configuration ISO from the `cloud-init.vendor-data` and `cloud-init.user-data` configuration keys and attach it to a virtual machine. The `cloud-init` that is running inside the VM then detects the drive on boot and applies the configuration.

  This source type is applicable only to VMs.

  To add such a device, use the following command:

      incus config device add <instance_name> <device_name> disk source=cloud-init:config

VM `agent`

  You can generate an `agent` configuration ISO which will contain the agent binary, configuration files and installation scripts. This is required for environments where `9p` isn’t supported and where an alternative way to load the agent is required.

  This source type is applicable only to VMs.

  To add such a device, use the following command:

      incus config device add <instance_name> <device_name> disk source=agent:config

Tmpfs

  You can back a disk device with an in-memory file system by using the `tmpfs:` source.

      incus config device add <instance_name> <device_name> disk source=tmpfs: path=<path_in_instance> [size=<size>] [initial.uid=<uid>] [initial.gid=<gid>] [initial.mode=<mode>]

  Both `source` and `path` are required. This creates a `tmpfs` mount inside the instance and supports optional properties for size, ownership, and permissions.

Tmpfs with overlayfs behavior

  If you want the same tmpfs behavior but combined with overlayfs semantics, use `tmpfs-overlay:` as the source.

      incus config device add <instance_name> <device_name> disk source=tmpfs-overlay: path=<path_in_instance> [size=<size>] [initial.uid=<uid>] [initial.gid=<gid>] [initial.mode=<mode>]

  Both `source` and `path` are required. Additionally, the target `path` must already exist inside the container. This provides an ephemeral in-memory file system with overlayfs handling.

## Initial volume configuration for instance root disk devices

Initial volume configuration allows setting specific configurations for the root disk devices of new instances. These settings are prefixed with `initial.` and are only applied when the instance is created. This method allows creating instances that have unique configurations, independent of the default storage pool settings.

For example, you can add an initial volume configuration for `zfs.block_mode` to an existing profile, and this will then take effect for each new instance you create using this profile:

    incus profile device set <profile_name> <device_name> initial.zfs.block_mode=true

You can also set an initial configuration directly when creating an instance. For example:

    incus init <image> <instance_name> --device <device_name>,initial.zfs.block_mode=true

Note that you cannot use initial volume configurations with custom volume options or to set the volume’s size.

## `initial.uid`, `initial.gid` and `initial.mode`

`initial.uid`, `initial.gid` and `initial.mode` apply in three different scenarios:

- On root disk devices, they are passed to the storage driver to set the ownership and mode of the instance’s root volume at creation time (when supported by the driver).

- On `tmpfs:` and `tmpfs-overlay:` disk devices, they are translated into `uid=`, `gid=` and `mode=` mount options for the underlying `tmpfs` mount.

- On custom volume disks where the `source` includes a sub-path (for example `source=myvol/sub/path`), they are used as the ownership and mode of any sub-directory that has to be created automatically when the device is started.

In all cases, `initial.uid` and `initial.gid` default to `0` and `initial.mode` defaults to `0711` (octal).

## Device options

`disk` devices have the following device options:

`attached`

Only for VMs: Whether the disk is attached or ejected

Key: | `attached`
Type: | bool
Default: | `true`
Required: | no

`boot.priority`

Boot priority for VMs (higher value boots first)

Key: | `boot.priority`
Type: | integer
Required: | no

`ceph.cluster_name`

The cluster name of the Ceph cluster (required for Ceph or CephFS sources)

Key: | `ceph.cluster_name`
Type: | string
Default: | `ceph`
Required: | no

`ceph.user_name`

The user name of the Ceph cluster (required for Ceph or CephFS sources)

Key: | `ceph.user_name`
Type: | string
Default: | `admin`
Required: | no

`dependent`

Specifies if the disk is instance dependent

Key: | `dependent`
Type: | bool
Default: | `false`
Required: | no

`initial.*`

Initial volume configuration for instance root disk devices

Key: | `initial.*`
Type: | string
Required: | no

For root disk devices, this is used to override the storage pool’s default volume configuration when creating the instance’s root volume.

For custom volumes, only `initial.uid`, `initial.gid` and `initial.mode` are accepted and they are used when auto-creating sub-directories inside the custom volume (when the `source` includes a sub-path that doesn’t exist).

`initial.uid`, `initial.gid` and `initial.mode` are also used to set the ownership and mode of the file system when the `source` is `tmpfs:` or `tmpfs-overlay:`.

`io.bus`

Only for VMs: Override the bus for the device

Key: | `io.bus`
Type: | string
Default: | `virtio-scsi` for block, `auto` for file system
Required: | no

This controls what bus a disk device should be attached to.

For block devices (disks), this is one of:

- `nvme`

- `virtio-blk`

- `virtio-scsi` (default)

- `usb`

For file systems (shared directories or custom volumes), this is one of:

- `9p`

- `auto` (default) (`virtiofs` if possible, else `9p`)

- `virtiofs`

`9p` doesn’t support hotplugging and `virtiofs` doesn’t support live migration. `auto` tries to use `virtiofs` if possible (`migration.stateful` not set to `true` and host support for `virtiofsd`) and falls back to `9p` otherwise.

`io.cache`

Only for VMs: Override the caching mode for the device

Key: | `io.cache`
Type: | string
Default: | `none`
Required: | no

This controls what bus a disk device should be attached to.

For block devices (disks), this is one of:

- `none` (default)

- `writeback`

- `unsafe`

For file systems (shared directories or custom volumes), this is one of:

- `none` (default)

- `metadata`

- `unsafe`

`limits.max`

I/O limit in byte/s or IOPS for both read and write (same as setting both `limits.read` and `limits.write`)

Key: | `limits.max`
Type: | string
Required: | no

`limits.read`

I/O limit in byte/s (various suffixes supported, see Units for storage, memory and network limits) or in IOPS (must be suffixed with `iops`) - see also Configure I/O limits

Key: | `limits.read`
Type: | string
Required: | no

`limits.write`

I/O limit in byte/s (various suffixes supported, see Units for storage, memory and network limits) or in IOPS (must be suffixed with `iops`) - see also Configure I/O limits

Key: | `limits.write`
Type: | string
Required: | no

`path`

Path inside the instance where the disk will be mounted (only for file system disk devices)

Key: | `path`
Type: | string
Required: | yes

This controls which path inside the instance the disk should be mounted on.

With containers, this option supports mounting file system disk devices, and paths and single files within them.

With VMs, this option supports mounting file system disk devices and paths within them. Mounting single files is not supported.

`pool`

The storage pool to which the disk device belongs (only applicable for storage volumes managed by Incus)

Key: | `pool`
Type: | string
Required: | no

`propagation`

Controls how a bind-mount is shared between the instance and the host (can be one of `private`, the default, or `shared`, `slave`, `unbindable`, `rshared`, `rslave`, `runbindable`, `rprivate`; see the Linux Kernel shared subtree documentation for a full explanation)

Key: | `propagation`
Type: | string
Required: | no

`raw.mount.options`

File system specific mount options

Key: | `raw.mount.options`
Type: | string
Required: | no

`readonly`

Controls whether to make the mount read-only

Key: | `readonly`
Type: | bool
Default: | `false`
Required: | no

`recursive`

Controls whether to recursively mount the source path

Key: | `recursive`
Type: | bool
Default: | `false`
Required: | no

`required`

Controls whether to fail if the source doesn’t exist

Key: | `required`
Type: | bool
Default: | `true`
Required: | no

`shift`

Sets up a shifting overlay to translate the source UID/GID to match the instance (only for containers)

Key: | `shift`
Type: | bool
Default: | `false`
Required: | no

`size`

Disk size in bytes (various suffixes supported, see Units for storage, memory and network limits) - only supported for the `rootfs` (`/`)

Key: | `size`
Type: | string
Required: | no

`size.state`

Same as `size`, but applies to the file-system volume used for saving runtime state in VMs

Key: | `size.state`
Type: | string
Required: | no

`source`

Source of a file system or block device (see Types of disk devices for details)

Key: | `source`
Type: | string
Required: | yes

`wwn`

Only for VMs: Set the disk World Wide Name (only supported on `virtio-scsi` bus)

Key: | `wwn`
Type: | bool
Default: | ``
Required: | no