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.
For clarity: It just stopped doing backups, silently. No error messages, no notifications, nothing. Just no backups for around two months. On my laptop, I only noticed because I was trying to restore a file and the latest backup was from December. On my desktop, I had a Thunderbolt external drive as a secondary backup.
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 Now
I 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.
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