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Creating a disk snapshot

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A disk snapshot is a copy of the disk file system at a specific point in time.

You can only create snapshots of replicated network disks. To work with non-replicated disks and disks on dedicated hosts, use Yandex Cloud Backup (the service is at the Preview stage and only supports Ubuntu and CentOS).

Preparation

A disk snapshot only contains the data that was already written to the disk when the snapshot was created. If the disk is attached to a running VM, the cache of the apps and OS will not be included in the snapshot.

To ensure the integrity of the snapshot data:

Linux systems:

  1. Stop all disk write operations in applications.

  2. Write the OS cache to the disk:

    sync

  3. Freeze the file system:

    sudo fsfreeze --freeze <mount_point>

    Where --freeze is the parameter to freeze the file system. Instead of <mount_point>, specify the folder the file system is connected to. For example, /mnt/vdc2.

  4. Create a snapshot following the instructions below.

  5. Unfreeze the file system:

    sudo fsfreeze --unfreeze <mount_point>

    Where --unfreeze is the parameter to unfreeze the file system. Instead of <mount_point>, specify the folder the file system is connected to. For example, /mnt/vdc2.

For other systems:

  1. Stop the virtual machine (see Stop).
  2. Wait until the VM status changes to STOPPED.

Creating a snapshot

To create a disk snapshot:

  1. In the management console, select the folder where the disk is located.

  2. Select Compute Cloud.

  3. On the left-hand panel, select Disks.

  4. In the row with the desired disk, click and select Create snapshot.

  5. Enter a name for the snapshot:

    • The length can be from 3 to 63 characters.
    • It may contain lowercase Latin letters, numbers, and hyphens.
    • The first character must be a letter. The last character can't be a hyphen.

  6. If necessary, enter a description of the snapshot.

  7. Click Create.

If you don't have the Yandex Cloud command line interface yet, install and initialize it.

The folder specified in the CLI profile is used by default. You can specify a different folder using the --folder-name or --folder-id parameter.

  1. View a description of the CLI create snapshot commands:

    yc compute snapshot create --help

  2. Select the disk to take a snapshot of. To get a list of disks in the default folder, run the command:

    yc compute disk list

    Result:

    +----------------------+--------------+-------------+---------------+--------+----------------------+-------------------------+
|          ID          |     NAME     |    SIZE     |     ZONE      | STATUS |     INSTANCE IDS     |       DESCRIPTION       |
+----------------------+--------------+-------------+---------------+--------+----------------------+-------------------------+
| a7lqgbt0bb9s40tifuhc | first-disk   | 20401094656 | ru-central1-a | READY  | a7lcvu28njbhnkcteb5n |                         |
| a7lv5j5hm1p1hppprga7 | second-disk  | 21474836480 | ru-central1-a | READY  |                      |                         |
+----------------------+--------------+-------------+---------------+--------+----------------------+-------------------------+

  3. Create a snapshot in the default folder:

    yc compute snapshot create \
  --name first-snapshot \
  --description "my first snapshot via CLI" \
  --disk-id fhm4aq4hvq5g3nepvt9b

    As a result, a disk snapshot is created with the name first-snapshot and description my first snapshot via CLI.

    • The length can be from 3 to 63 characters.
    • It may contain lowercase Latin letters, numbers, and hyphens.
    • The first character must be a letter. The last character can't be a hyphen.

If you don't have Terraform, install it and configure the Yandex Cloud provider.

  1. Describe the resource parameters in the yandex_compute_snapshot configuration file.

    Example configuration file structure:

    resource "yandex_compute_snapshot" "snapshot-1" {
  name           = "disk-snapshot"
  source_disk_id = "<disk ID>"
}

    For more information on resources that you can create with Terraform, see the provider documentation.

  2. Make sure that the configuration files are correct.

    1. In the command line, go to the directory where you created the configuration file.

    2. Run the check using the command:

      terraform plan

    If the configuration is described correctly, the terminal displays a list of created resources and their parameters. If the configuration contain errors, Terraform will point them out.

  3. Deploy the cloud resources.

    1. If the configuration doesn't contain any errors, run the command:

      terraform apply

    2. Confirm that you want to create the resources.

    Afterwards, all the necessary resources are created in the specified folder. You can check that the resources are there with the correct settings using the management console.

A snapshot is created asynchronously. The snapshot is created with the Creating status immediately after the create command is run. From this point on, you can resume writing data to disk, and disk operations will not affect the data in the snapshot.

Once the snapshot has been created, the snapshot status will change to Ready. From this point on, you can use the snapshot to create images, populate disks, and so on.

Alert

When creating a snapshot or image in Linux, the UUID and PARTUUID of disk partitions are saved. Linux uses this data when mounting partitions, including the root one, so the IDs must be unique. For example, if you clone a boot disk and attach it to the same VM, two partitions with the same UUIDs appear on the VM. As a result, after starting the VM, the root partition may not be the one you specified as the boot disk.

To avoid this, attach the disk to the VM and change all the duplicate UUIDs. Learn more in the instructions for attaching disks.

See also

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