> ## Documentation Index
> Fetch the complete documentation index at: https://docs.nebius.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Attaching and mounting Compute volumes to VMs
In this article, you will learn how to use [Compute disks and shared filesystems](./types) on virtual machines (VMs).
This article only covers additional volumes: non-boot disks and shared filesystems. You add a boot disk when you create a VM.
After [creating a disk](./manage#how-to-create-a-disk) or a [shared filesystem](./manage#how-to-create-a-shared-filesystem), you need to do the following to use it on a VM:
1. [Attach it to the VM](#how-to-attach-volumes-to-vms) by using Nebius AI Cloud interfaces.
2. [Mount it to the VM](#how-to-mount-volumes-to-vms) inside the VM's operating system.
A VM and its volumes must be located in the same project. For more details about projects and resource hierarchy in Nebius AI Cloud, see [How resources, identities and access are managed in Nebius AI Cloud](/iam/overview).
## How to attach volumes to VMs
To attach disks or shared filesystems to a VM:
* **New VM**
On the VM creation page ( **Compute** → **Virtual machines** → **Create virtual machine**), do the following:
1. Click **Attach disk** or **Attach shared filesystem**.
2. Set up the volume:
1. Select whether you want to add a new or existing volume.
If an existing disk is already added to another VM, you cannot add it to the new VM. A filesystem can be shared by multiple VMs.
2. For a new volume, set its [parameters](/compute/storage/manage#volume-parameters).
3. Set a device ID if you are adding a disk, or a mount tag if you are attaching a filesystem. Device IDs and mount tags are used to [mount volumes to VMs](/compute/storage/use#how-to-mount-volumes-to-vms).
3. Click the attach-volume button at the end of the window.
When you click **Create and add disk** or **Create and attach filesystem**, the disk or filesystem is created immediately and [charged](../resources/pricing#volumes-disks-and-shared-filesystems) separately even if you remove it from the VM later or do not proceed with creating the VM.
4. If you want to [manually mount the filesystem](#shared-filesystems) that you added to the VM, turn off the **Auto mount** option for the filesystem.
By default, Compute automatically mounts filesystems that you add to VMs via the web console.
If you add a disk, you always need to [mount it manually](#disks).
* **Existing VM**
**Disks**
1. In the sidebar, go to **Compute** → **Virtual machines**.
2. Open the page of the required VM.
3. Switch to the **Disks** tab.
4. Click **Attach resource** → **Disk**.
5. Select whether you want to attach a new or existing disk.
If an existing disk is already attached to another VM, you cannot attach it to a new VM.
6. For a new disk, set its [parameters](/compute/storage/manage#volume-parameters).
7. Set a device ID for the disk. Device IDs are used to [mount disks to VMs](/compute/storage/use#how-to-mount-volumes-to-vms).
8. Click the attach-volume button at the end of the window.
**Shared filesystems**
1. In the sidebar, go to **Compute** → **Virtual machines**.
2. Open the page of the required VM.
3. If the VM is not in the `Stopped` status, click **Stop VM** and then confirm the action.
4. After the VM has the `Stopped` status, switch to the **Filesystems** tab.
5. Click **Attach resource** → **Filesystem**.
6. Select whether you want to attach a new or existing filesystem.
A filesystem can be shared by multiple VMs.
7. For a new filesystem, set its [parameters](/compute/storage/manage#volume-parameters).
8. Set a mount tag for the filesystem. Mount tags are used to [mount filesystems to VMs](/compute/storage/use#how-to-mount-volumes-to-vms).
9. Click the attach-volume button at the end of the window.
1. [Create the volumes](./manage).
2. Create the following files locally:
* `secondary_disk.json` to attach disks:
```json theme={null}
[
{
"attach_mode": "",
"existing_disk": {
"id": ""
},
"device_id": ""
}
]
```
Where:
* Write permission, `READ_WRITE` (default) or `READ_ONLY`.
* `existing_disk.id`: Disk ID to be added. To get the ID, run `nebius compute disk list`.
* `device_id`: Disk device ID. This parameter is different from `existing_disk.id`, as `device_id` is used for [mounting a disk to a VM](/compute/storage/use#disks).
Create your own device ID, such as `my-disk`. Make sure that it is unique within a VM.
If you do not specify the device ID, it takes the `disk-N` default value where `N` is an integer. For example, `disk-0`.
* `filesystem.json` to attach shared filesystems:
```json theme={null}
[
{
"attach_mode": "",
"existing_filesystem": {
"id": ""
},
"mount_tag": ""
}
]
```
Where:
* Write permission, `READ_WRITE` (default) or `READ_ONLY`.
* `existing_filesystem.id`: Filesystem ID to be attached. To get the ID, run nebius compute filesystem list.
* `mount_tag`: Tag for [mounting a filesystem to a VM](#shared-filesystems).
Create your own tag, such as `my-filesystem`. Make sure that it is unique within a VM.
If you do not specify the tag, it takes the `filesystem-N` default value where `N` is an integer. For example, `filesystem-0`.
3. Create or update a VM with the volumes configured:
* To **create a VM**, run the following command:
```bash theme={null}
nebius compute instance create \
--secondary-disks "$(cat secondary_disk.json)" \
--filesystems "$(cat filesystem.json)" \
```
* To **attach disks to an existing VM**, run the following command:
```bash theme={null}
nebius compute instance update \
--patch \
--secondary-disks "$(cat secondary_disk.json)"
```
To get the ID of an existing VM, run nebius compute instance list.
The `--patch` parameter allows you to only update the specified parameters. Without it, the command resets the VM settings to their default values.
* To **attach shared filesystems to an existing VM**, stop the VM first:
```bash theme={null}
nebius compute instance stop --id
```
Then update the VM:
```bash theme={null}
nebius compute instance update \
--patch \
--filesystems "$(cat filesystem.json)"
```
After the update, start the VM:
```bash theme={null}
nebius compute instance start --id
```
## How to mount volumes to VMs
### Disks
1. [Attach the disk to a VM](#how-to-attach-volumes-to-vms).
2. If you have not saved the disk's device ID, for example, when adding it to the VM, get it from the information about the VM:
```bash theme={null}
nebius compute instance get --id --format json \
| jq -r --arg disk_id \
'.spec.secondary_disks[]
| select(.existing_disk.id == $disk_id)
| .device_id'
```
To get the VM ID, run nebius compute instance list. To get the disk ID, run nebius compute disk list.
3. [Connect to the VM over SSH](../virtual-machines/connect#connect-to-the-vm-using-ssh).
4. Switch to the `root` user:
```bash theme={null}
sudo su -
```
5. Partition the device. For example, you can use `cfdisk`. In the example below, we assume that you have named the device `disk-0`; for disks, all device IDs are prefixed with `virtio-`:
1. Run `cfdisk`:
```bash theme={null}
cfdisk /dev/disk/by-id/virtio-disk-0
```
Referring to a device by its name, e.g., `/dev/vdb`, does not guarantee it will function properly. Use the device ID instead, e.g., `/dev/disk/by-id/virtio-disk-0`.
2. Under **Select label type**, select **gpt** and press **Enter**.
3. Select **New** (partition) and press **Enter**.
4. Enter the partition size and press **Enter**. This will create a `/dev/disk/by-id/virtio-disk-0-part1` partition.
5. Select **Write** (the partition table to the device) and press **Enter**, then type `yes` and press **Enter**.
6. Select **Quit** and press **Enter**.
6. Format the partition:
```bash theme={null}
mkfs.ext4 /dev/disk/by-id/virtio-disk-0-part1
```
7. Mount the partition and configure permissions for it by using `chmod`. In the example below, the partition is mounted at `/mnt/disk-0`, and all VM users are granted write access to it:
```bash theme={null}
mkdir /mnt/disk-0
mount /dev/disk/by-id/virtio-disk-0-part1 /mnt/disk-0
chmod a+w /mnt/disk-0
```
8. If you want the partition to be mounted automatically after every VM restart, add it to `/etc/fstab` by its UUID:
```bash theme={null}
echo "UUID=$(blkid -s UUID -o value /dev/disk/by-id/virtio-disk-0-part1) /mnt/disk-0 ext4 defaults,nofail 0 2" >> /etc/fstab
```
Do not omit `nofail`. If it is not specified and the VM cannot find the partition on restart (for example, the disk has been repartitioned), the VM will not boot.
9. Exit the `root` user shell:
```bash theme={null}
exit
```
### Shared filesystems
If you create a VM in the web console, you can automatically attach and mount a shared filesystem to the VM by using the **Auto mount** option. If you do not use it, mount the filesystem manually. To do this:
1. [Attach the shared filesystem to a VM](#how-to-attach-volumes-to-vms).
2. If you have not saved the filesystem's mount tag, for example, when adding it to the VM, get the mount tag from the information about the VM:
```bash theme={null}
nebius compute instance get --id --format json \
| jq -r --arg fs_id \
'.spec.filesystems[]
| select(.existing_filesystem.id == $fs_id)
| .mount_tag'
```
To get the VM ID, run nebius compute instance list. To get the disk ID, run nebius compute filesystem list.
3. [Connect to the VM over SSH](../virtual-machines/connect#connect-to-the-vm-using-ssh).
4. Switch to the `root` user:
```bash theme={null}
sudo su -
```
5. Mount the filesystem as a `virtiofs` device and configure permissions for it by using `chmod`. In the example below, a filesystem has the mount tag `filesystem-0` and is mounted at `/mnt/fs`. All VM users are granted write access to it:
```bash theme={null}
mkdir /mnt/fs
mount -t virtiofs filesystem-0 /mnt/fs
chmod a+w /mnt/fs
```
6. If you want the filesystem to be mounted automatically after every VM restart, add it to `/etc/fstab`:
```bash theme={null}
echo "filesystem-0 /mnt/fs virtiofs rw,nofail 0 0" >> /etc/fstab
```
Do not omit `nofail`. If it is not specified and the VM cannot find the filesystem on restart (for example, it has been deleted), the VM will not boot.
7. Exit the `root` user shell:
```bash theme={null}
exit
```
## See also
* [How to detach additional volumes from virtual machines](./detach-volume)
* [Types of storage volumes in Compute](./types)
* [Creating and resizing Compute volumes](./manage)
* [How to create a virtual machine in Nebius AI Cloud](../virtual-machines/manage)