Detach an Amazon EBS volume from an Amazon EC2 instance - Amazon EBS
ConsiderationsUnmount and detach a volumeTroubleshoot

Detach an Amazon EBS volume from an Amazon EC2 instance

You need to detach an Amazon Elastic Block Store (Amazon EBS) volume from an instance before you can attach it to a different instance or delete it. Detaching a volume does not affect the data on the volume.

Considerations

  • You can detach an Amazon EBS volume from an instance explicitly or by terminating the instance. However, if the instance is running, you must first unmount the volume from the instance.

  • If an EBS volume is the root device of an instance, you must stop the instance before you can detach the volume.

  • You can reattach a volume that you detached (without unmounting it), but it might not get the same mount point. If there were writes to the volume in progress when it was detached, the data on the volume might be out of sync.

  • After you detach a volume, you are still charged for volume storage as long as the storage amount exceeds the limit of the AWS Free Tier. You must delete a volume to avoid incurring further charges. For more information, see Delete an Amazon EBS volume.

Unmount and detach a volume

Use the following procedures to unmount and detach a volume from an instance. This can be useful when you need to attach the volume to a different instance or when you need to delete the volume.

Step 1: Unmount the volume

From your Linux instance, use the following command to unmount the /dev/sdh device.

[ec2-user ~]$ sudo umount -d /dev/sdh

From your Windows instance, unmount the volume as follows.

  1. Start the Disk Management utility.

    • (Windows Server 2012 and later) On the taskbar, right-click the Windows logo and choose Disk Management.

    • Windows Server 2008) Choose Start, Administrative Tools, Computer Management, Disk Management.

  2. Right-click the disk (for example, right-click Disk 1) and then choose Offline. Wait for the disk status to change to Offline before opening the Amazon EC2 console.

Step 2: Detach the volume from the instance

To detach the volume from the instance, use one of the following methods:

Console
To detach an EBS volume using the console

  1. Open the Amazon EC2 console at https://console.aws.amazon.com/ec2/.

  2. In the navigation pane, choose Volumes.

  3. Select the volume to detach and choose Actions, Detach volume.

  4. When prompted for confirmation, choose Detach.

AWS CLI
To detach an EBS volume from an instance using the AWS CLI

After unmounting the volume, use the detach-volume command.

Tools for Windows PowerShell
To detach an EBS volume from an instance using the Tools for Windows PowerShell

After unmounting the volume, use the Dismount-EC2Volume command.

Step 3: (Windows instances only) Uninstall the offline device locations

When you unmount and detach a volume from an instance, Windows flags the device location as offline. The device location remains offline after rebooting, and stopping and restarting the instance. When you restart the instance, Windows might mount one of the remaining volumes to the offline device location. This causes the volume to be unavailable in Windows. To prevent this from happening and to ensure that all volumes are attached to online device locations the next time Windows starts, perform the following steps:

  1. On the instance, open the Device Manager.

  2. In the Device Manager, select View, Show hidden devices.

  3. In the list of devices, expand the Storage controllers node.

    The device locations to which the detached volumes were mounted are named AWS NVMe Elastic Block Storage Adapter and they should appear greyed out.

  4. Right-click each greyed out device location named AWS NVMe Elastic Block Storage Adapter, select Uninstall device and choose Uninstall.

    Important

    Do not select the Delete the driver software for this device check box.

Troubleshoot

The following are common problems encountered when detaching volumes, and how to resolve them.

Note

To guard against the possibility of data loss, take a snapshot of your volume before attempting to unmount it. Forced detachment of a stuck volume can cause damage to the file system or the data it contains or an inability to attach a new volume using the same device name, unless you reboot the instance.

  • If you encounter problems while detaching a volume through the Amazon EC2 console, it can be helpful to use the describe-volumes CLI command to diagnose the issue. For more information, see describe-volumes.

  • If your volume stays in the detaching state, you can force the detachment by choosing Force Detach. Use this option only as a last resort to detach a volume from a failed instance, or if you are detaching a volume with the intention of deleting it. The instance doesn't get an opportunity to flush file system caches or file system metadata. If you use this option, you must perform the file system check and repair procedures.

  • If you've tried to force the volume to detach multiple times over several minutes and it stays in the detaching state, you can post a request for help to AWS re:Post. To help expedite a resolution, include the volume ID and describe the steps that you've already taken.

  • When you attempt to detach a volume that is still mounted, the volume can become stuck in the busy state while it is trying to detach. The following output from describe-volumes shows an example of this condition:

    "Volumes": [
    {
        "AvailabilityZone": "us-west-2b",
        "Attachments": [
            {
                "AttachTime": "2016-07-21T23:44:52.000Z",
                "InstanceId": "i-fedc9876",
                "VolumeId": "vol-1234abcd",
                "State": "busy",
                "DeleteOnTermination": false,
                "Device": "/dev/sdf"
            }
        ...
    }
]

    When you encounter this state, detachment can be delayed indefinitely until you unmount the volume, force detachment, reboot the instance, or all three.