I have recently upgraded to OS X 10.8. Rooting around in directory /Volumes revealed a directory MobileBackups. Descending therein led me to what seemed to be several clones of my whole disk. Directory /Volumes/MobileBackups/Backups.backupdb/NormHardy holds these files:
drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-080612 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-105601 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-115600 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-133349 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-142452 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-21-194842 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-22-075526 drwxr-xr-x@ 3 root wheel 102 Apr 22 13:22 2013-04-22-094833 lrwxrwxrwx 0 root wheel 0 Apr 22 09:48 Latest -> 2013-04-22-094833It was pleasant to note that /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-194842/Macintosh HD/Volumes was empty thus avoiding infinite recursion.
If you know a little Unix lore you know that the inode of a file or directory is a very low level number that rather directly tells the disk hardware where to find said directory or file. The option -i on the shell command ls reveals the inode of the item. Shell command ls -li work4 yields 72057602630651821 -rw-r--r--@ 1 norm staff 139 Mar 13 2011 work4 which is a file I have not changed in many months. (72057602630651821 = 0x1000002002a8fad = 0x100000200000000 + 2789293) (- (string->number "1000002002a8fad" 16) (string->number "100000200000000" 16))
$ ls -li /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-194842/"Macintosh HD"/Users/norm/work4 72057602630651821 -rw-r--r--@ 1 norm staff 139 Mar 13 2011 … $ ls -li /Users/norm/work4 2789293 -rw-r--r--@ 1 norm staff 139 Mar 13 2011 /Users/norm/work4 $ vi work4I add a blank character to file. Time passes, indeed an hour mark:
$ ls -li /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-194842/"Macintosh HD"/Users/norm/work4 72057602655002000 -rw-r--r--@ 1 norm staff 139 Mar 13 2011 /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-194842/Macintosh HD/Users/norm/work4 $ ls -li /Users/norm/work4 27139470 -rw-r--r--@ 1 norm staff 141 Apr 22 13:59 /Users/norm/work4 $ ls -li /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-115600/"Macintosh HD"/Users/norm/work4 ls -li /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-080612/"Macintosh HD"/Users/norm/work4 72057602655002000 -rw-r--r--@ 1 norm staff 139 Mar 13 2011 /Volumes/MobileBackups/Backups.backupdb/NormHardy/2013-04-21-080612/Macintosh HD/Users/norm/work4Both inode numbers have changed as a result of the edit but it remains the case that the two old versions of the file have the same inode—not the same before and after the edit.