Most pages that come up when google researching tell you to...
1) enable unsupported drives with
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
2) create a sparsebundle locally
3) copy it to your network share
...but forget the last crucial step:
In the root of the sparsebundle, create a file com.apple.TimeMachine.MachineID.plist containing:
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>com.apple.backupd.HostUUID</key>
<string>YOURUUIDHERE</string>
</dict>
</plist>
where YOURUUIDHERE is a string containing dashes which can be obtained from
> system_profiler | grep UUID
I could have saved myself a lot of hours of frustration if I could have found this link more easily. The bash script hosted there in particular works wonders. With this knowledge I was able to change an existing Time Machine backup's UUID to match that of my current machine and get into the backup to restore files. I can't explain how happy I am about that.
