That’s a first I’ve heard of this. No one has posted on here, that I’ve seen, as of yet either. Maybe another Community member has?

If you have a case, may be try posting on the Forums as well, and include case #, to see what PMs have to say...or confirm a bug?

Case #07083882   Cannot find Linux guest credentials. 

Hi @Moose - generally...if you post on the Forums, they require the # over there. We don’t here 

@Moose Please review the hosts and servers from Inventory and Backup Infrastructure to ensure no error or warning after the upgrade to 12.1.

I would check this and also check the stored credentials for Linux machines if you are doing the App Aware processing on them.  The other option if you don’t need application-aware then disable it for those systems in your jobs.

Chris makes a good point. I haven’t used guest processing in yrs...not even for DB servers (we do in-app backups within the guest OS). Always caused more headaches than it’s worth...for me, at least. 

We have discovered that combination backup tags seem to be an issue, because if we separate into individual backup tags.  The backup is working.

Interesting behavior 

But, it was working in v12 & earlier I presume? I wonder what developmental change they made to cause this issue to occur? 

yes, it was working on V12

That is interesting as the tag behavior from v12 to 12.1 should not have changed but maybe it did?  Glad to hear you worked it out.