Hi All,
Wanted to drop a note here describing a problem I was having with TimeMachine and a new TrueNAS server, it took longer than it should have to stumble over someone’s bug report and fix. I’m sharing it here where other folks might find it more easily.
I set up a fresh install of TrueNAS (25.10.4 - Goldeye) and had run a backup from my laptop without any issues.
Then I moved the NAS to another location and reconfigured the pool to something fancier and, sigh, backups started failing with a permission error.
I didn’t have any trouble setting up the backup destination (in fact, I could watch the share get mounted while working through the dialogue) but then I’d get an almost instant failure when I started a backup. When I expanded the notification it would warn me that I needed to re-add the user or password. I spent a long time making sure that I had all of my ducks in a row, assuming it was something funky I’d done with my TrueNAS setup.
I finally stumbled across Dmitry Porotnikov’s description and workaround for the bug in his post: Time Machine backup failure to Linux/Samba target - Missing kown [SIC] server marker, it seems that there’s a list of hosts that are recognized as backup servers and unless the destination is in the list, the system won’t share the auth into.
His post has a nice explanation and he provides a little script that fixes things. Here’s his original:
PL='/private/var/root/Library/Group Containers/group.com.apple.NetworkAuthorization.ServerMarkers/serverMarkers.plist'
sudo cp "$PL" "$PL.bak.$(date +%Y%m%d-%H%M%S)"
sudo /usr/libexec/PlistBuddy -c 'Print' "$PL"
sudo /usr/libexec/PlistBuddy -c 'Add :"192.168.88.99" bool true' "$PL" 2>/dev/null || \
sudo /usr/libexec/PlistBuddy -c 'Set :"192.168.88.99" true' "$PL"
sudo plutil -p "$PL"
In my case, I replaced the IP addresses (192.168.88.99) with the mDNS domain name my server was using (truenas.local), ran the script, rebooted, and backups started working.