"Multiple connections to a server or shared resource" Error


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Colin Hamilton
Colin Hamilton
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Setup MR on a family members Windows PC to backup to a NAS and it has been running successfully for a month, however last few weeks the "Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed." error appears each time the unattended backup tries to run.  Backups run fine when started manually.

I have double checked it is set to use the Macrium Task Scheduler and the "Use Windows System account to run scheduled tasks" is not selected.

Any advice on getting this to start working again would be appreciated. 
jphughan
jphughan
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SMB connections to a NAS are per-user, not system-wide.  It sounds like somehow the SYSTEM account context, which is where scheduled backups occur, might have some sort of stuck connection under different credentials than Reflect is trying to use.  That would prevent Reflect from opening another connection using separate credentials (hence the error) but would not prevent backups that are launched in the context of your own user session.  But if that's the case, a simple restart should solve that.

Patrick O'Keefe
Patrick O'Keefe
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This might be an instance of Windows allowing a user to have only one set of network credentials for a NAS.  That restriction is part of Windows' SMB support.  The scheduled task runs under the "NT AUTHORITY\SYSTEM" user name.  If that system account already has a set of credentials for that NAS your scheduled backup will fail if it needs a different set of credentials.  If you manually start the backup from the Definition Files tab, the backup will run under your userid which may have the required credentials (or none at all).

Does this sound like your problem?  If so I can mention some circumventions, but that would be a lot of useless verbiage if your problem lies somewhere else.

Colin Hamilton
Colin Hamilton
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jphughan - 27 September 2021 7:41 PM
SMB connections to a NAS are per-user, not system-wide.  It sounds like somehow the SYSTEM account context, which is where scheduled backups occur, might have some sort of stuck connection under different credentials than Reflect is trying to use.  That would prevent Reflect from opening another connection using separate credentials (hence the error) but would not prevent backups that are launched in the context of your own user session.  But if that's the case, a simple restart should solve that.

Both the NAS and the PC have been restarted several times, but unfortunately it makes no difference. Thank you anyway.
Colin Hamilton
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Patrick O'Keefe - 27 September 2021 7:49 PM
This might be an instance of Windows allowing a user to have only one set of network credentials for a NAS.  That restriction is part of Windows' SMB support.  The scheduled task runs under the "NT AUTHORITY\SYSTEM" user name.  If that system account already has a set of credentials for that NAS your scheduled backup will fail if it needs a different set of credentials.  If you manually start the backup from the Definition Files tab, the backup will run under your userid which may have the required credentials (or none at all).

Does this sound like your problem?  If so I can mention some circumventions, but that would be a lot of useless verbiage if your problem lies somewhere else.

It does....

"verbiage" appreciated.
jphughan
jphughan
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While Patrick elaborates, any chance you're using a batch file or PS/VBS script to perform your backups rather than a basic definition file?  If so, have you customized it to include creating any network connections or drive mappings prior to the portion of the script that starts the backup?

Patrick O'Keefe
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Colin Hamilton - 27 September 2021 8:38 PM
Patrick O'Keefe - 27 September 2021 7:49 PM
...
Does this sound like your problem?  If so I can mention some circumventions, but that would be a lot of useless verbiage if your problem lies somewhere else.

It does....

"verbiage" appreciated.
  1. I think the first thing to check is whether the two sets of credentials are really needed.   If both your System credentials aren't needed you can delete them.  Or if your System-based connection and your Reflect connections could use the same set of credentials you could pick just one of them.  (But you might have to change the privileges of the userid on the NAS.  That may not be desirable.)
  2. Windows is sort of dumb about this; the credential saving process doesn't notice if an IP address and a DNS host name point to the same device.  So you could use the IP address for your backups and the host name for the existing System connection.
  3. If your NAS has a static IP address you can use the C:\Windows\System32\drivers\etc\hosts file to define a new host name for the NAS.
  4. If your router's DNS service allows you to add definitions you use CNAME records to define alias names for the NAS.  The advantage of this is that all your computers will get the same set of names.  Also, if you decide to move the share containing your backups to a different NAS you have just one place to change the name mapping.



jphughan
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Patrick O'Keefe - 27 September 2021 9:24 PM
  1. I think the first thing to check is whether the two sets of credentials are really needed.   If both your System credentials aren't needed you can delete them.  Or if your System-based connection and your Reflect connections could use the same set of credentials you could pick just one of them.  (But you might have to change the privileges of the userid on the NAS.  That may not be desirable.)
  2. Windows is sort of dumb about this; the credential saving process doesn't notice if an IP address and a DNS host name point to the same device.  So you could use the IP address for your backups and the host name for the existing System connection.
  3. If your NAS has a static IP address you can use the C:\Windows\System32\drivers\etc\hosts file to define a new host name for the NAS.
  4. If your router's DNS service allows you to add definitions you use CNAME records to define alias names for the NAS.  The advantage of this is that all your computers will get the same set of names.  Also, if you decide to move the share containing your backups to a different NAS you have just one place to change the name mapping.



Re #1, connections in the interactive user session and the SYSTEM context would not interfere with each other, and there are solid use cases for using different credentials in those two areas.  For example, a user might give Reflect read/write credentials to their NAS as is needed for making backups, while using read-only credentials for the persistent connection that exists in their user session.  The idea is that a user will only need to be able to browse backups rather than modify or delete them, and restricting the persistent connection to read-only access is a mitigation against ransomware.

Re #2, that's true, but that workaround shouldn't be necessary here.

Re #3, I strongly disagree with this approach.  I can't tell you how many times people have created problems by using hosts file entries.  They add something there as a workaround, then much farther down the line it creates some problem, but by that point they've forgotten they even made that change, so they pull their hair out trying to diagnose the problem.  I work in IT and a surprising number of IT admins don't even know the hosts file exists, which would of course complicate troubleshooting.  I've also seen cases where some team member makes that change, and of course never documents it, then leaves the company, and their replacements have no idea about it.  The hosts file is a relic of a long bygone era, and it is a dirty, filthy workaround that is likely to cause you more hurt than it spares you.

Re #4, I've never seen a router-hosted DNS environment that allows creating CNAMEs, except maybe third-party firmware packages that can be flashed onto some routers.  But even if that's possible, I'm not sure the benefit of being able to cut over to a new NAS that for some reason can't take over the name of the replaced NAS is worth the effort.  And while it won't affect NAS-hosted shares, I'll note that Windows by default will refuse incoming SMB connections that used a CNAME rather than a hostname.  You have to set a registry key on the file server to allow it to accept SMB connections that used a CNAME.  So if you WERE using a Windows-hosted share, this setup wouldn't work without some additional work.

Patrick O'Keefe
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Re #1, connections in the interactive user session and the SYSTEM context would not interfere with each other, and there are solid use cases for using different credentials in those two areas. For example, a user might give Reflect read/write credentials to their NAS as is needed for making backups, while using read-only credentials for the persistent connection that exists in their user session. The idea is that a user will only need to be able to browse backups rather than modify or delete them, and restricting the persistent connection to read-only access is a mitigation against ransomware.

I obviously did not word my comment very well. 

I understand that connections are currently independent and do not interfere with each other, but the current situation does not work.

I was assuming that the OP wanted SYSTEM to be able to run the backup that now works under the OP's userid (which I assume is what you mean by "the interactive user session".  If so the current SYSTEM connection and the backup are going to have to use the same credentials.  That means the userid associated with those credentials would have to both whatever NAS permissions associated with the current SYSTEM's use and whatever NAS permissions needed for the backup.

Re #2, that's true, but that workaround shouldn't be necessary here.

#2, #3, and #4 all assume that there are 2 SMB connections to the NAS and the OP needs both of these (with different credentials for each) to run under SYSTEM.  If that assumption is wrong then nothing that I've said applies to the situation and can be ignored.  But if the assumption is correct then I think Windows has to be fooled into thinking that the SMB connections are associated with different remote hosts.  Using host name for one connection and IP address for the other provides a solution (although not a very appealing one). 

Re #3, I strongly disagree with this approach. I can't tell you how many times people have created problems by using hosts file entries. ...

I absolutely agree with you.  This is a terrible solution, but it works.  I used it for a while when I needed both a public and a private share on the same NAS.  In the end I bout another NAS for the public share.

Re #4, I've never seen a router-hosted DNS environment that allows creating CNAMEs, except maybe third-party firmware packages that can be flashed onto some routers. ...

The Merlin firmware for ASUS routers - 3rd party firmware, but based on official ASUS firmware and developed in close cooperation with ASUS - provides this support.  I use it to provide a NAS with 2 names ... for uses unrelated to SMB connections.  I've never tried it for multiple SMB connection with different sets of credentials but I'll try it this evening.  Maybe my brilliant scheme doesn't work at all.

Edited 28 September 2021 1:13 AM by Patrick O'Keefe
Colin Hamilton
Colin Hamilton
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Patrick O'Keefe - 27 September 2021 9:24 PM
Colin Hamilton - 27 September 2021 8:38 PM
Patrick O'Keefe - 27 September 2021 7:49 PM
...
Does this sound like your problem?  If so I can mention some circumventions, but that would be a lot of useless verbiage if your problem lies somewhere else.

It does....

"verbiage" appreciated.
  1. ....
  2. Windows is sort of dumb about this; the credential saving process doesn't notice if an IP address and a DNS host name point to the same device.  So you could use the IP address for your backups and the host name for the existing System connection.
  3. ....



Have been chatting to MR support and it was point 2 that fixed the issue. 

The Windows user account connection to the NAS uses the UNC address and we changed the backup definition file to use the IP address rather than UNC.  This seems to trick Windows into thinking it is two different devices and as such success.

Thanks for all the support and help....
GO

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