TIL: Apple Broke Time Machine Again on Tahoe

Summary

So… Here we are again. Today, after a minor disaster with my Obsidian vault, I decided to restore from Time Machine, and… I realized that it had silently broken across both my Tahoe machines. I use a Synology NAS as Time Machine target, exporting the share over SMB and that has worked flawlessly for years, but this came as a surprise because I could have sworn it was working fine a couple of months ago–but no, it wasn’t. After some research, I found out that the issue is with Apple’s unilateral decision to change their SMB defaults (without apparently notifying anyone), and came across a few possible fixes. What Seems To Be Working NowI found this gist, which I am reproducing here for posterity, that seems to be working for me, but which entails editing the nsmb.conf file on the Mac itself–which is not exactly ideal, since I’m pretty sure Apple will break this again in the future. sudo nano /etc/nsmb.conf # I used vim, of course …and adding the following lines (the file should be empty): [default] signing_required=yes streams=yes soft=yes dir_cache_max_cnt=0 protocol_vers_map=6 mc_prefer_wired=yes The explanation here is that macOS Tahoe changed the default from signing_required=no to stricter control, and NAS devices with relaxed SMB settings cannot handle this without explicit configuration. Another common pitfall is name encoding issues in machine names, so you should remove Non-ASCII Characters from the .sparsebundle name (that wasn’t an issue for me, but YMMV). On the Synology side, the recommendation was to go to Control Panel > File Services > SMB > Advanced and set: Maximum SMB protocol: SMB3 Enable Opportunistic Locking: Yes Enable SMB2 Lease: Yes Enable SMB Durable Handles: Yes Server signing: No (or “Auto”) Transport encryption: Disabled That doesn’t quite match my DSM UI, but it’s close enough, and my settings now look like this: My SMB settings, as of DSM 7.3.2-86009-1 My Backup Backup PlanSince I’m tired of Apple breaking Time Machine every few years a...