I'm trying to backup to a NAS box but I'm getting the following error:

Cannot open backup device '\\nas02\backup\SQL\instance\Full-Backups\OtherDBs\Daily\MGMT_TEST.bak'. Operating system error 1326(failed to retrieve text for this error. Reason: 15105).
Msg 3013, Level 16, State 1, Line 2
BACKUP DATABASE is terminating abnormally.

This was working before and I have checked permissions to the location by logging onto the server as the account sql is running under and I can go to the location above. From there i can create new files and update existing ones etc.

  • There is no space limitation
  • The user running the statement is a sysAdmin

I'm thinking some permissions of some type but struggling to see how.

  • Check to make sure you haven't exceeded a space limitation Sep 5 '16 at 13:56
  • Is there any additional information in the Sql Logs? Can you restart that server? Perhaps some AD authentication has gotten out of whack. Can you use XP_CMDSHELL to copy a file to the target? Can you 'read' a file from that target? Is this running in a Sql Job? Sep 5 '16 at 14:04
  • I get the following in sql log which is more or less the same:Message BackupDiskFile::CreateMedia: Backup device '\\nas02\Backup\SQL\instnace\TransactionLogShipping\db_test' failed to create. Operating system error 1326(failed to retrieve text for this error. Reason: 15105). I cant restart as its a production server so would need to schedule this in. I think the your right its AD getting out of sync ect. It wont read a file either doing a restore headeronly for example Sep 5 '16 at 14:12
  • Does the file you're backing up to already exist on the target? If it does, was it created with an expiration date? Can you delete it and retry? are you using WITH INIT? Sep 5 '16 at 14:18
  • Also check Windows Events Sep 5 '16 at 14:21

It means either it's permission issue or you are running out of space on target.

Permission Issue

The service account of SQL Server (which used to start SQL Server service) does not have access to the target.


Find SQL Server Service > Right click and go to PROPERTIES.

Go to LogOn/Security tab

If it's system account (NETWORK SERVICE, LOCAL SYSTEM etc.) then change it to any specific account (domain account like ex. dba\sqlserviceact).

Then restart SQL Server Service.

And grant the account (ex. dba\sqlserviceact) read & write privilege on the shared folder (network path).

If it's other then system account the grant the account ready/write privilege.


  • This is not the case the service account has access as mentioned ive logged on as this account and can access this location. Sep 5 '16 at 14:15
  • Because you are performing backup on SQL Server, So, the account SQL Server running through, should have read/write access on the shared target. Sep 5 '16 at 14:18
  • 1
    If UserA has access (who is performing backup) and SQL Server Service account does not have access to the target. You will face same error. Sep 5 '16 at 14:19

Check the permissions for the service account running the sql service and the job also has read/write permissions for the folder on the nas box. there is a gui for a Nas box you can configure this in




Thanks for all the responses it turned out to be the connection between the SQL servers and the QNAP device lost authentication with Active Directory.

I made some changes to how the permissions are calculated on the shared backup folders from the QNAP to being managed in windows.


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