To create or change a VM's boot disk, seeCreate a boot diskandDetach and reattach a boot disk,respectively.

To create a new disk, seeCreate a new Persistent Disk volumeandCreate a new Hyperdisk volume.

Required roles and permissions

To get the permissions that you need to attach a disk to a VM, ask your administrator to grant you the following IAM roles on the project:

• Compute Instance Admin (v1) (roles/compute.instanceAdmin.v1)
• To connect to a VM instance that can run as a service account: Service Account User (v1) (roles/iam.serviceAccountUser role)

For more information about granting roles, seeManage access to projects, folders, and organizations.

These predefined roles contain the permissions required to attach a disk to a VM. To see the exact permissions that are required, expand theRequired permissions section:

You might also be able to get these permissions withcustom roles or otherpredefined roles.

Disk attachment mode

When you attach a disk to a VM, you indicate how the VM can access the data onthe disk by specifying the disk attachment mode. You can choose read-onlyor read-write mode.

The default mode is read-write.

Share a disk between VMs

You can share the same disk between VMs so that each VM can simultaneouslyaccess the disk by attaching the disk to each VM. You can attach a disk to multipleVMs if the disk's type and the VM's machine type support it.

To attach a disk to multiple VMs, follow the procedure inAttach a non-boot disk to your VM for each VM.

You must use the same disk attachment mode for all VMs that you attach the diskto. For example, you can't attach a disk to one VM in read-write mode andattach it at the same time to another VM in read-only mode.

For information about attaching a disk to multiple VMs, including the supporteddisk types, seeShare a disk between VMs.

Attaching a Hyperdisk volume to multiple VMs

To attach a Hyperdisk volume to multiple VMs, make sure thedisk's access mode is set to an appropriate value for your use case. Forinstructions on setting the access mode, seeset the disk's access mode.

When you attach a Hyperdisk volume to a VM, you must choose adisk attachment mode that doesn't conflict with the disk's access mode. For example,you can't use read-only attachment mode with a disk that's in single-writer ormulti-writer mode.

Limitations

When attaching a disk to a VM, be aware of the following limitations:

• A disk must be in the same zone as the VM that you want to attach it to.For regional disks, the VM must be in the same zone as one of thedisk's replicas.

• You can attach up to 127 secondary, non-boot, zonal disks to a VM.

• You can't attach a disk to a VM if doing so will exceed theHyperdisk size and attachment limits.

• The following disk types don't support read-only mode:

  • Hyperdisk Balanced
  • Hyperdisk Balanced High Availability
  • Hyperdisk Throughput
  • Hyperdisk Extreme

• When you attach a disk to multiple VMs, you must use the same disk attachmentmode for all the VMs.

• When you attach a disk to multiple VMs, additional restrictions apply. See therestrictions for sharing a disk between VMs inread-only mode andmulti-writer mode.

• Disks attached to multiple VMs don't support auto-delete, that is, theycan't be automatically deleted when the VM is deleted.

Attach a non-boot disk to a VM

You can attach a non-boot zonal disk to a VM by using the Google Cloud console,the Google Cloud CLI, or REST.

When attaching a disk to a VM, keep the following points in mind:

• Use a custom device name: Google recommends that you specify a customdevice name when attaching a disk to a VM. The name you specify is used togenerate asymlink for the disk in theguest OS, which makes it easier to identify and manage disks on the VM.

  Caution: If you add a custom device name to a disk after you attach the diskto a VM, Compute Engine temporarily detaches the disk from the VM, whichmight disrupt your workloads.

• Attaching a disk to multiple VMs: To attach a disk to multiple VMs, repeatthe procedure in this section for each VM. You must use the same disk attachmentmode for all VMs that you attach the disk to.

To attach aRegional Persistent Disk orHyperdisk Balanced High Availability volume to your VM,see insteadAttach a regional disk to your VM.

gcloud compute instances attach-diskVM_NAME \    --diskDISK_NAME --device-name=DEVICE_NAME    --modeDISK_ATTACHMENT_MODE

resource "google_compute_instance" "test_node" {  name         = "test-node"  machine_type = "f1-micro"  zone         = "us-west1-a"  boot_disk {    initialize_params {      image = "debian-cloud/debian-11"    }  }  attached_disk {    source      = google_compute_disk.default.id    device_name = google_compute_disk.default.name  }  network_interface {    network = "default"    access_config {      # Ephemeral IP    }  }  # Ignore changes for persistent disk attachments  lifecycle {    ignore_changes = [attached_disk]  }}

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/VM_NAME/attachDisk{   "source": "/compute/v1/projects/PROJECT_ID/zones/ZONE/disks/DISK_NAME",   "deviceName":DEVICE_NAME,   "mode" : "DISK_ATTACHMENT_MODE"}

After you attach a disk to a VM, connect to the VM and enable the VM's operatingsystem (OS) to use the disk:

• If you attached a blank disk, format and mount the disk
• If you attached a non-empty disk, mount the disk

Learn how to format and mount your new disks onLinuxorWindows VMs.

What's next

• Prevent data loss by regularlybacking up your disks with snapshots
• Useregional persistent disksfor synchronous replication between two zones.