We've had this question come up from our customers more than once after new firmware was installed on the dedup appliance, or some other reason BUE and the OST login isn’t working.
The command is spauser. From the BUE 2010 admin guide page 1589 Symantec Backup Exec Deduplication Option
Changing the password for the logon account for a deduplication storage folder
When you specify a Backup Exec logon account for a deduplication storage folder, an additional user account is created for the deduplication components with the same user name and password. However, if you change the credentials for the
Sharing a deduplication device between multiple media servers
Backup Exec logon account, the credentials for the additional user account are not changed automatically. You must use the spauser.exe utility to update the password for the additional user account. This account is known as the “User 1” account when you use the spauser.exe utility to view a list of user names that are associated with the deduplication storage folder.
To change the password for the logon account for a deduplication storage folder
1 On the Backup Exec Network menu, click Logon Accounts.
2 Select the Backup Exec logon account that you want to change, and then click Edit.
3 Click Change Password. 4 Type the new password. 5 Click OK. 6 At a command prompt, type the following command:
spauser.exe -c -u
The user name is case-sensitive . If you do not know the user name, type the following command to find the user name that is associated with “User 1”:
spauser.exe -l
You will be prompted for the old password and a new password. Be sure that the new password is the same as the password that you used in step 4.
See “About deduplication storage folders” on page 1579.