How to mount the existing shared disk to Linux VM

Lin Hua 0

I created a shared disk and shared it to 2 Linux VMs.

According to the following page's instruction, I prepare a new empty disk with partprobe command on 1st VM, but when I tried to mount it to the 2nd vm, I don't want to format the disk again, but it seems like I can't retrieve the disk partition information.

https://learn.microsoft.com/en-us/azure/virtual-machines/linux/add-disk?tabs=ubuntu

VasimTamboli 4,420

To mount an existing shared disk to a Linux VM without formatting it again, you can follow these steps:

Attach the Shared Disk to the Second VM:

In the Azure portal, navigate to the second Linux VM.
Under "Settings," select "Disks" and click on "Attach existing" to attach the shared disk you created.

Choose the appropriate disk from the list and click on "OK" to attach it to the VM.

1. Identify the Disk Partition:

      - SSH into the second Linux VM.

- Use the following command to list the available disks and their partitions:

lsblk

Identify the shared disk and its corresponding partition. It will typically be listed as /dev/sdc or similar.

Mount the Disk Partition:

Create a mount point directory where you want to mount the shared disk. For example, /mnt/shared-disk:

sudo mkdir /mnt/shared-disk

Mount the disk partition to the mount point directory:

sudo mount /dev/sdc1 /mnt/shared-disk

3. Validate the Mount:

Check if the shared disk is successfully mounted by listing the contents of the mount point directory:

ls /mnt/shared-disk

The shared disk should now be mounted on the second Linux VM without formatting it again. You can access and use the shared data on the disk from the /mnt/shared-disk directory.

Note: Make sure to replace /dev/sdc1 with the appropriate disk partition identifier for your environment. Use the lsblk command to identify the correct partition.

Lin Hua 0 Reputation points

2023-06-05T10:37:01.2566667+00:00

I executed the following command,

sudo mount /dev/sdc1 /mnt/shared-disk

but got the error msg on the 2nd vm like:

mount: special device /dev/sdc1 does not exist

Looking forward to your comment, thanks.
VasimTamboli 4,420 Reputation points

2023-06-05T11:12:49.64+00:00
Check if the Disk is Attached: Confirm that the shared disk is successfully attached to the second Linux VM. You can check this by going to the Azure portal, navigating to the VM's "Disks" settings, and verifying that the shared disk is listed as attached.

Verify Disk and Partition Identifier: SSH into the second Linux VM and use the following command to list the available disks and their partitions:

lsblk

Ensure that the shared disk (/dev/sdc or similar) and its corresponding partition (/dev/sdc1 or similar) are listed in the output. Note down the correct disk and partition identifiers.

Check Disk Availability: Run the following command to rescan the SCSI bus and make sure the OS detects the newly attached disk:

bash sudo partprobe /dev/sdc

After running the above command, re-run the lsblk command to verify if the disk and partition are now available.

Mount the Disk: Once the disk and partition are correctly identified and available, you can proceed with mounting the shared disk using the appropriate disk and partition identifiers:

bash sudo mount /dev/sdc1 /mnt/shared-disk

Make sure to replace /dev/sdc1 with the correct disk partition identifier you obtained from the lsblk command.

If the above steps still don't resolve the issue, there might be some other configuration or connectivity problems specific to your environment. In such cases, it would be helpful to provide additional information about your setup or consider reaching out to Azure support for further assistance.
Lin Hua 0 Reputation points

2023-06-05T11:52:46.5366667+00:00
Thanks a lot VasimTamboli

After executing

sudo partprobe /dev/sdc

it seems like we can retrieve the formatting information from shared disk, and I can mount the /dev/sdc1 to /mnt/share-disk on the vm2.

but when I touched 2 files (test.file, test2.file) on vm1 /mnt/share-disk and execute ls command on the vm2 /mnt/share-disk, but only test.file was listed, @VasimTamboli would please comment, really appreciate !!
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deherman-MSFT 33,701 Reputation points Microsoft Employee

2023-06-13T16:07:01.5333333+00:00

@Lin Hua

If you still have questions, please let us know in the "comments" and we would be happy to help you. Comment is the fastest way of notifying the experts.

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1 answer

deherman-MSFT 33,701 Reputation points Microsoft Employee

2023-06-05T18:56:06.6366667+00:00

@Lin Hua

The above information provided is not correct. Shared disks cannot be mounted and managed like regular disks. You need to use a cluster manager, like Windows Server Failover Cluster (WSFC), or Pacemaker, that handles cluster node communication and write locking. This is because traditional file systems aren't designed for simultaneous access and can result in data corruption if two systems try to write to the same area of the disk at the same time. You can find examples of Supported OS and the cluster manager here.

If you don't want to setup a cluster manager but want to access the same directory from multiple VMs then I would suggest using either Azure Files NFS or Azure Blob Storage with Blobfuse.

If you still have questions, please let us know in the "comments" and we would be happy to help you. Comment is the fastest way of notifying the experts.

If the answer has been helpful, we appreciate hearing from you and would love to help others who may have the same question. Accepting answers helps increase visibility of this question for other members of the Microsoft Q&A community.

Thank you for helping to improve Microsoft Q&A!
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