Azure Files
An Azure service that offers file shares in the cloud.
Port 2049 is open, but neither the Azure nor the on-premises network can reach it.
Connection to 10.101.255.4 2049 port [tcp/nfs] succeeded!
nfs connectivity issuses
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Shing Fan LEE
20
Reputation points
I haven't been able to connect to my NFS all day, and it is still down.
Azure Files
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Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator2026-07-01T21:21:07.95+00:00 Hello Shing Fan LEE,
You’re seeing NFS connectivity issues—if your NFS share has been down all day, the root cause is often one of a few common Azure Files NFS conditions: missing NFS client packages, network/firewall blocking port 2049, storage account network access (untrusted client), or secure-transfer/encryption settings mismatch.Here are the most useful checks to try for Azure Files NFS:
1) Confirm the NFS utilities are installed (Linux)
Before mounting, install one of:
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nfs-utils(RHEL/CentOS/Oracle Linux) -
nfs-client(SLES) -
nfs-common(Ubuntu/Debian)
Example install commands:
- RHEL/CentOS:
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sudo yum install nfs-utils(orsudo dnf install nfs-utilson newer versions) - Ubuntu:
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sudo apt update && sudo apt install nfs-common
2) Verify port 2049 is reachable
Azure Files NFS uses TCP 2049. Make sure it’s open from the client to the storage account’s NFS endpoint.
Run from the client:
sudo nc -zv <storageaccountname>.file.core.windows.net 2049If this fails, your firewall/NSG/network path is likely blocking port 2049.
3) If it is “untrusted,” ensure correct endpoint configuration
For NFS, auth is based on network security rule configuration (not user-based auth). If you are from an untrusted network/IP, mounting can fail.
Use one of:
- Service endpoint
- Private endpoint
(For on-prem access with private connectivity requirements, you may also need VPN/ExpressRoute.)
4) Check Secure transfer / encryption-in-transit settings for NFS mounts
If the storage account enforces secure transfer/encryption in transit for NFS, mounting can fail—especially if you’re not using the recommended mount helper.
For NFS encryption-in-transit:
- Use the AZNFS Mount Helper for NFSv4.1 TLS tunnels, or
- Disable the relevant secure settings on the storage account (per the guidance) if you don’t need encrypted-in-transit NFS.
5) Double-check you’re mounting with the right options/protocol version
Incorrect mount options can cause mount failures (for example, errors like “incorrect mount option”). Also ensure both sides use compatible NFS versions (Azure Files NFS is commonly mounted as NFSv4.1).
Can you please update us if the action plan provided was helpful?
Should there be any follow-up questions or concerns, please let us know and we shall try to address them.
If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
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2 answers
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Shing Fan LEE 20 Reputation points
2026-07-02T13:19:12.49+00:00 -
Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator
2026-07-02T18:29:47.1433333+00:00 Thank you for the update.
Since the connectivity test to port 2049 was successful, this indicates that the network path to the NFS endpoint is reachable and the issue is likely occurring during the NFS mount process rather than due to a basic connectivity block.
To help narrow down the cause of the
mount.nfs: Remote I/O error, could you please provide the following details:- The exact mount command being used (please redact any sensitive information).
- Confirmation that the Azure file share was created as an NFS file share and not an SMB file share, as mounting an SMB share using NFS can result in a Remote I/O error.
- The Linux distribution and version.
- Whether the storage account is configured with a Private Endpoint or Service Endpoint.
The output of:
- nslookup <storage-account-name>.file.core.windows.net
and
- sudo mount -vvv -t nfs <mount-command>
Additionally, if Encryption in Transit is enabled for the NFS share, please confirm whether you are using the AZNFS mount helper, as Azure Files NFS with encryption in transit requires the appropriate mount method.
Can you please update us if the action plan provided was helpful?
Should there be any follow-up questions or concerns, please let us know and we shall try to address them.
If these answer your question, click "Upvote" which may be beneficial to other community members reading this thread.
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Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator
2026-07-05T19:15:41.9633333+00:00 Hello Shing Fan LEE,
Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions.
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Harshavardhan Sriramula 0 Reputation points Microsoft External Staff Moderator
2026-07-06T21:43:59.28+00:00 Hello Shing Fan LEE,
Following up to see if you had a chance to check the above response and if it was helpful. Please let me know if you have any questions.
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Shing Fan LEE 20 Reputation points
2026-07-02T13:46:51.39+00:00 i got the following return when i do mount
mount.nfs: Remote I/O error