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What are the proper xattr in Time Machine folder hierarchy?

Hi there,


this is a highly technical question as I am trying to reconnect a corrupt Time Machine volume to its original Macs, one of them running SL, the other Yosemite.


I tried what Pondini advises on his website, including a migration of the network preferences. When first plugging the TM volume, I get this in the Console:


16/01/15 02:32:12 com.apple.backupd[38751] Starting standard backup

16/01/15 02:32:12 com.apple.backupd[38751] Backing up to: /Volumes/TW2/Backups.backupdb

16/01/15 02:32:13 com.apple.backupd[38751] Detected system migration from: /Volumes/Time Machine/Backups.backupdb/snowy/2014-09-16-141637/Macintosh HD

16/01/15 02:33:19 com.apple.backupd[38751] Backup content size: 646.7 GB excluded items size: 444.5 GB for volume Macintosh HD

16/01/15 02:33:19 com.apple.backupd[38751] Starting pre-backup thinning: 242.65 GB requested (including padding), 69.61 GB available

16/01/15 02:33:19 com.apple.backupd[38751] No expired backups exist - deleting oldest backups to make room

16/01/15 02:33:19 com.apple.backupd[38751] Error: backup disk is full - all 0 possible backups were removed, but space is still needed.

16/01/15 02:33:19 com.apple.backupd[38751] Backup Failed: unable to free 242.65 GB needed space

16/01/15 02:33:24 com.apple.backupd[38751] Backup failed with error: Not enough available disk space on the target volume.


I don't understand how it can detect a migration but still can't delete older backups on this drive to make room.


MAC address

So I followed a rather old link on MacOSX Hints to reset the MAC address on the drive, and now I have:

drwxrwxr-x@ 9 cubytus staff 986 15 jan 22:01 .
drwxrwxrwt@ 174 root admin 5916 16 jan 01:41 ..
-rw-r--r-- 1 root staff 0 15 jan 22:01 .0026b0XXXXXX
-rw-r--r-- 1 root staff 0 15 jan 20:25 .3c0754XXXXXX
-rw-r--r--@ 1 cubytus staff 15364 16 jan 01:34 .DS_Store
drwx------ 4 cubytus staff 170 19 nov 04:45 .Spotlight-V100
drwxrwxrwt 4 cubytus staff 136 19 nov 04:45 .TemporaryItems
d-wx-wx-wt 3 cubytus staff 102 16 jan 01:41 .Trashes
-rw-r--r-- 1 cubytus staff 162570 4 déc 23:27 .VolumeIcon.icns
-rw-r--r-- 1 cubytus staff 302 13 déc 14:58 .apdisk
-rw-r--r-- 1 cubytus staff 0 4 déc 23:27 .com.apple.timemachine.donotpresent
-rw-r--r-- 1 cubytus staff 0 4 déc 23:27 .com.apple.timemachine.supported
-rw-r--r-- 1 cubytus staff 785 4 déc 23:27 .disk_label
-rw-r--r-- 1 cubytus staff 3149 4 déc 23:27 .disk_label_2x
drwx------@ 2 cubytus staff 748 16 jan 01:39 .fseventsd
-rw-r--r-- 1 cubytus staff 0 16 jan 02:07 .keepThisDriveSpinning
drwxr-xr-x 2 cubytus staff 68 17 aoû 2013 .prpro.scratch
drwxr-xr-x 2 cubytus staff 68 31 mai 2008 .vol
drwxr-xr-x@ 4 cubytus staff 204 16 jan 01:44 Backups.backupdb
lrwxr-xr-x 1 cubytus staff 11 26 fév 2009 etc -> private/etc
-r-xr-xr-x 1 cubytus staff 47712 24 sep 2007 fsaclctl
-rw-r--r-- 1 cubytus staff 10310496 9 déc 00:41 mach_kernel
-rwxr-xr-x 1 cubytus staff 115716 9 déc 00:41 tmbootpicker.efi
lrwxr-xr-x 1 cubytus staff 11 26 fév 2009 tmp -> private/tmp
lrwxr-xr-x 1 cubytus staff 11 26 fév 2009 var -> private/var


The MAC address in 3c belongs to the Snow Leopard Machine, the 00 one to the Yosemite machine. I know it sounds weird, but it is unclear how TM recognizes its backup drive. I first disabled ACL with fsaclctl (taken from a Leopard install DVD), and it worked, as said by:

sudo /Volumes/TW2/fsaclctl -p /Volumes/TW2

Access control lists are not supported or currently disabled on /Volumes/TW2.


Made sure the hidden file with the MAC address was correct, then re-enabled the ACLs.


ACLs and Xattr

Since the internal HDD had to be replaced, I wrote the com.apple.backupd.SnapshotVolumeUUID with the new HDD UUID in directory "Backups.backupdb/snowy/Latest":


Latest cubytus$ sudo xattr -w com.apple.backupd.SnapshotVolumeUUID 361B184E-E1FF-3860-95E2-XXXXXXXXXXAE "Macintosh HD"


Then went up two levels and checked the xattr:


Backups.backupdb cubytus$ ls -al@

total 0

drwxr-xr-x@ 4 cubytus staff 204 16 jan 01:44 .

com.apple.FinderInfo 32

drwxrwxr-x@ 9 cubytus staff 986 15 jan 22:01 ..

com.apple.FinderInfo 32

drwxr-xr-x@ 14 cubytus staff 578 15 jan 20:39 snowy

com.apple.backupd.BackupMachineAddress 17

com.apple.backupd.HostUUID 36

com.apple.backupd.ModelID 13

drwxr-xr-x@ 31 cubytus staff 1088 16 jan 02:18 Whitebook

com.apple.FinderInfo 32

com.apple.backupd.BackupMachineAddress 17

com.apple.backupd.HostUUID 36

com.apple.backupd.ModelID 10


And checked their content:


snowy:Backups.backupdb cubytus$ sudo xattr -l Whitebook/

com.apple.FinderInfo:

00000000 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|

00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0B |................|

00000020

com.apple.backupd.BackupMachineAddress: 00:26:b0:XX:XX:XX

com.apple.backupd.HostUUID: BBD6D268-F58D-5407-974E-XXXXXXXXXXXX

com.apple.backupd.ModelID: MacBook5,2

snowy:Backups.backupdb cubytus$ sudo xattr -l snowy/

com.apple.backupd.BackupMachineAddress: 3c:07:54:XX:XX:XX

com.apple.backupd.HostUUID: 94BE92F5-E652-546C-8B33-XXXXXXXXXXXX

com.apple.backupd.ModelID: MacBookPro8,1


Each computer has the correct addresses and HostUUID, i.e. the current ones.

Yet neither of those give the "Reuse existing backups" shown on Pondini's website, and tmutil on Yosemite doesn't succeed in reconnecting to the backups.

What is the point I am missing?

MacBook Pro, Mac OS X (10.6.8), 2.8 GHz i7, 16GB RAM

Posted on Jan 16, 2015 11:56 AM

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What are the proper xattr in Time Machine folder hierarchy?

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