SQL SERVER – Cannot open backup device. Operating system error 1326 (Logon failure: unknown user name or bad password.)

There might be various reasons for above error, but this case is very specific to a situation where SQL Server was installed on a machine which was in Workgroup whereas the backup destination was the server located in the domain.  Here is the error message seen in SQL Agent job history. Let us learn about how to fix Operating system error 1326.

Executed as user: NT Service\SQLSERVERAGENT. Microsoft (R) SQL Server Execute Package Utility Version 11.0.2100.60 for 64-bit Copyright (C) Microsoft Corporation. All rights reserved.
Started: 12:23:24 PM Progress: 2016-12-27 12:23:25.00 Source: {229AB1E3-E7E5-4185-B305-BF0F7657122A}
Executing query “DECLARE @Guid UNIQUEIDENTIFIER EXECUTE msdb..sp…”.: 100% complete End Progress Error: 2016-12-27 12:23:25.35 Code: 0xC002F210 Source: Back Up Database Task Execute SQL Task
Description: Executing the query “BACKUP DATABASE [master] TO DISK = N’\\192.168.3….” failed with the following error: “Cannot open backup device ‘\\192.168.3.55\backupShare\master_backup_2016_12_27_122325_2407734.bak’. Operating system error 1326(Logon failure: unknown user name or bad password.). BACKUP DATABASE is terminating abnormally.”. Possible failure reasons: Problems with the query, “ResultSet” property not set correctly, parameters not set correctly, or connection not established correctly. End Error

Generally, when the backup is taken SQL Agent Service account is used to take backup. In this case since SQL was on Workgroup, it was NT Service\SQLSERVERAGENT. This account is not a valid account to validate for a domain.

VERIFICAITON

First, let’s verify that we are hitting the same issue which I experienced. From Workgroup machine, we would try to query remote share using xp_cmdshell. Here is the command.

xp_cmdshell 'dir \\192.168.3.55\backupShare'

This command should fail with below error.

Logon failure: unknown user name or bad password.

SOLUTION

Since we are talking about authentication issue. So, we need to make sure that we map a drive to SQL Server (not windows). As per SQL Server Books-On-Line:

“For a network share to be visible to SQL Server, the share must be mapped as a network drive in the session in which SQL Server is running”

Here is the command to map the drive.

EXEC XP_CMDSHELL 'net use Z: \\192.168.3.55\backupShare password@123 /User:domain\user'

Once the above is completely successful, we should be able to see content on the Z drive by running below command.

EXEC XP_CMDSHELL 'dir Z:\'

After this we should be able to take backup on the Z drive as its mapped within SQL Server as a drive.

Backup database master to disk = 'Z:\master.bak'

The above command should work and create the backup file in \\192.168.3.55\backupShare

Have you encountered this error earlier? Did you find this solution interesting? Please comment and let me know.

Reference: Pinal Dave (https://blog.sqlauthority.com)