Hello,
I’m trying to setup a Backup which saves files from a SMB Shared Folder. I’m using Duplicati as a service with an extra service user. After setting the “snapshot-policy” option to “Required” I get the following errorr message in attachment… The service user got local administration rights on both PCs…thanks for help 
Hello
Not possible. No one can do a snapshot on another computer. End of story. Other backup software manage this by installing an agent on the backed up computer, the agent is doing the snapshot, but these are high end backup software such as Veeam.
So the only thing you can do is install the backup software on your ‘server’.
Shared from what? If Windows, what version exactly? Microsoft once tried to allow this in a server version.
EDIT:
VSS for SMB File Shares describes it but I don’t know if the 2012 plan ever worked,or where it stands now.
I searched my Windows 10 system, and see neither the fssagent.dll nor fssprov.dll that it mentions.
You could check your systems. It might be possible to get another view using vssadmin list providers.
Basically it looks like maybe it’s possible under just the right conditions, but there are a lot of questions to it.
[MS-FSRVP]: File Server Remote VSS Protocol is a protocol description, but that’s just a piece of a puzzle.
